Associated top production in ATLAS and CMS

A set of measurements of top quark pair and single top quark production in association with standard model (SM) bosons performed by the CMS and ATLAS Collaborations is presented. The consistency of these results among themselves and with the SM prediction is discussed. The latest results on four top quark production are also shown

A Careful Design for a Tool to Detect Child Pornography in P2P Networks

This paper addresses the social problem of child pornography on peer-to-peer (P2P) networks on the Internet and presents an automated system with effective computer and telematic tools for seeking out and identifying data exchanges with pedophilic content on the Internet. The paper analyzes the social and legal context in which the system must operate and describes the processes by which the system respects the rights of the persons investigated and prevents these tools from being used to establish processes of surveillance and attacks on the privacy of Internet users

Una propuesta de enseñanza del área y perímetro para estudiantes de 4° en un contexto rural

En el presente documento se muestra de manera general, el diseño de una serie de actividades enfocadas a la enseñanza del área y perímetro en estudiantes de cuarto grado, por medio del establecimiento de un espacio rectangular, reconociendo las unidades totales que lo componen, y la longitud que lo delimita, a partir de procesos de recubrimiento de un terreno; gracias a su aplicación dentro de un contexto rural, haciendo uso de la resolución de problemas como metodología de enseñanza

Defluidization and agglomeration of a fluidized bed reactor during Cynara cardunculus L. gasification using sepiolite as a bed material

This work studies the defluidization time and the agglomerate generation in a bubbling fluidized bed (BFB) reactor during Cynara cardunculus L. gasification using, separately, two different bed materials, silica sand and sepiolite 〖(MG〗_8 〖Si〗_12 O_30 (OH)_4 〖(OH〗_2)(_4^)8 H_2). The high adsorption capacity and the elemental composition of the sepiolite make it suitable as an alternative bed material in order to reduce agglomeration. Experiments were performed on a stainless steel lab-scale BFB reactor operating with air as a gasifying agent at different air excess ratios (u/umf). A quartz reactor was alternatively used for the visualization of bed material and biomass during gasification, allowing one to observe the agglomerate formation process. Pressure signals were analyzed both in time and frequency domain to determine the defluidization time. Furthermore, the shape and size of the bed material after the experiments were evaluated. Higher defluidization times in the case of sepiolite were measured. Particle sizes were affected by the type of bed material and the air excess and agglomerates of different shapes were formed for sepiolite and silica sand.Publicad

Distributor performance in a bubbling fluidized bed: Effects of multiple gas inlet jet and bubble generation

This study considers the role of the distributor effect during the bubble generation, growth and interaction within a bubbling fluidized bed. To characterize this effect, short-term and long-term dynamics are explored in time and frequency domains. Controversy occurs when inspecting what is actually known of the gas distribution mechanism in bubbling fluidized beds. To sustain discussion, classical and innovative techniques, such as Digital Image Analysis, DIA, and Wavelet Analysis WA, are used. As a result, the conclusion is that the distributor not only has no effect in the averaged long-term dynamics but also has no effect on the general bubble generation characteristic frequencies. The analysis performed on the bubble generation region concludes that the distributor design has a great influence at the short-term scale such as during the bubble generation process controlling the spatial distribution of the bubble nucleation sites over the distributor plate

Solar multiple optimization of a DSG linear Fresnel power plant

Linear Fresnel power plants are currently one of the most promising concentrating solar power plants. However there are only a few commercial projects. These power plants have a lower efficiency than parabolic trough collector plants and are still expensive. To increase the efficiency of these plants, the utilization of water/steam in the receivers (direct steam generation, DSG) and thermal storage (TES) have been considered. As case study, a 50 MWe solar-only linear Fresnel power plant located in Seville, Spain is considered. The effects of the solar field size and the thermal storage size on the annual production of the plant are analyzed: Nine different solar field sizes and up to eight thermal storage sizes have been compared. An economic optimization is presented in order to determine which plant has lowest Levelized Cost of Electricity (LCOE). It has been found that for the power plants with no-storage the optimum solar multiple (SM) is 1.7, whereas for the cases with thermal storage, the optimum configuration is a larger solar field (SM = 2), with a thermal storage of 2 h

Estimation and experimental validation of the circulation time in a 2D gas-solid fluidized beds

The circulation time is defined as the time required for a group of particles to reach the freeboard from the bottom of a fluidized bed and return to their original height. This work presents an estimation and validation of the circulation time in a 2D gas solid bubbling fluidized bed under different operating conditions. The circulation time is based on the concept of the turnover time, which was previously defined by Geldart [1] as the time required to turn the bed over once. The equation tc,est =2Ah′/Qb is used to calculate the circulation time, where A is the cross section of the fluidized bed, h′ is the effective fluidized bed height and Qb is the visible bubble flow. The estimation of the circulation time is based on the operating parameters and the bub ble phase properties, including the bubble diameter, bubble velocity and bed expansion. The experiments for the validation were carried out in a 2D bubbling fluidized bed. The dense phase velocity was measured with a high speed camera and non intrusive techniques such as particle image velocimetry (PIV) and digital image analysis (DIA), and the experimental circulation time was calculated for all cases. The agreement between the theoretical and experimental circulation times was satisfactory, and hence, the proposed estimation can be used to reliably predict the circulation time.Publicad

Current Trends in Pan-European Identity Management Systems

The demand for electronic identity has grown as a result of governments? promotion of e-Government, in which the citizen-public administration relationship often has a strictly personal nature and requires digital identification systems that are univocal, secure, and global. The management of this identity by public administrations is an important challenge, accentuated when interoperability among public administrations of different countries become necessary. In this paper current trends in pan-euroean identity management systems are analysized and a outlook of the future European scenary is shown

District cooling network connected to a solar power tower

During the operation of solar power towers there are occasions, commonly in the summer season, where some of the heliostats have to stop focussing on the central receiver, located at the top of the tower, because the maximum thermal power that the receiver can withstand has been reached. The highest cooling demand takes place at these same occasions. In the present paper, the exceeding heliostats are focused to a second receiver, using the extra heat as a source of absorption chillers. The chilled water is used to cool buildings or offices, using a district cooling network, reducing greatly the electricity usage. In this work we have analysed the case of a circular field of heliostats focussing at an external receiver of 120 MW of thermal power. The thermal power of the exceeding heliostats is able to supply steam to eight absorption chillers that produce cold water for a population of more that 90000 people via a network of more than the 50 km. The economical analysis shows that the district cooling system is profitable and an advantageous option for the consumers, that can obtain up to 75% savings on their electricity bills.The authors would like to thank the financial support by the Spanish Ministry of Economy and Competitiveness under Project No. ENE2012-34255 as well as the MOSARELA (Molten salt receiver lab) project, IDI-20120128, supported by CDTI and S2m Solutions.Publicad

Solving identity delegation problem in the e-government environment

At present, many countries allow citizens or entities to interact with the government outside the telematic environment through a legal representative who is granted powers of representation. However, if the interaction takes place through the Internet, only primitive mechanisms of representation are available, and these are mainly based on non-dynamic offline processes that do not enable quick and easy identity delegation. This paper proposes a system of dynamic delegation of identity between two generic entities that can solve the problem of delegated access to the telematic services provided by public authorities. The solution herein is based on the generation of a delegation token created from a proxy certificate that allows the delegating entity to delegate identity to another on the basis of a subset of its attributes as delegator, while also establishing in the delegation token itself restrictions on the services accessible to the delegated entity and the validity period of delegation. Further, the paper presents the mechanisms needed to either revoke a delegation token or to check whether a delegation token has been revoked. Implications for theory and practice and suggestions for future research are discussed