On synchrony in dynamic distributed systems

[EN] Many modern distributed services are deployed in dynamic systems. Cloud services are an example. They are expected to provide service to a potentially huge amount of users and may require a wide geographical deployment in multiple data centres. Their service processes vary in volume in accordance with workload variations, showing an adaptive behaviour in order to minimise economical costs. Dynamic distributed systems may be classifed considering two axes: (a) the number of processes that compose the system, and (b) the diameter of the networking graph that interconnects those processes. Other important features of dynamic systems can be derived from these two characteristics, e.g., their attainable synchrony. We analyse the level of synchrony that may be achieved in each dynamic system class and revise the existing techniques for transforming an initially asynchronous large dynamic system into another one with a higher synchrony level. With this, a larger set of problems may be handled in dynamic distributed systems. This facilitates the implementation and provision of additional services in those systems.Muñoz-Escoí, FD.; Juan Marín, RD. (2018). On synchrony in dynamic distributed systems. Open Computer Science. 8(1):154-164. https://doi.org/10.1515/comp-2018-0014S1541648

The AVA Multi-View Dataset for Gait Recognition

In this paper, we introduce a new multi-view dataset for gait recognition. The dataset was recorded in an indoor scenario, using six convergent cameras setup to produce multi-view videos, where each video depicts a walking human. Each sequence contains at least 3 complete gait cycles. The dataset contains videos of 20 walking persons with a large variety of body size, who walk along straight and curved paths. The multi-view videos have been processed to produce foreground silhouettes. To validate our dataset, we have extended some appearance-based 2D gait recognition methods to work with 3D data, obtaining very encouraging results. The dataset, as well as camera calibration information, is freely available for research purpose

Pre-multisymplectic constraint algorithm for field theories

We present a geometric algorithm for obtaining consistent solutions to systems of partial differential equations, mainly arising from singular covariant first-order classical field theories. This algorithm gives an intrinsic description of all the constraint submanifolds. The field equations are stated geometrically, either representing their solutions by integrable connections or, what is equivalent, by certain kinds of integrable m-vector fields. First, we consider the problem of finding connections or multivector fields solutions to the field equations in a general framework: a pre-multisymplectic fibre bundle (which will be identified with the first-order jet bundle and the multimomentum bundle when Lagrangian and Hamiltonian field theories are considered). Then, the problem is stated and solved in a linear context, and a pointwise application of the results leads to the algorithm for the general case. In a second step, the integrability of the solutions is also studied. Finally, the method is applied to Lagrangian and Hamiltonian field theories and, for the former, the problem of finding holonomic solutions is also analized.Comment: 30 pp. Presented in the International Workshop on Geometric Methods in Modern Physics (Firenze, April 2005

CAP Theorem: Revision of its related consistency models

[EN] The CAP theorem states that only two of these properties can be simultaneously guaranteed in a distributed service: (i) consistency, (ii) availability, and (iii) network partition tolerance. This theorem was stated and proved assuming that "consistency" refers to atomic consistency. However, multiple consistency models exist and atomic consistency is located at the strongest edge of that spectrum. Many distributed services deployed in cloud platforms should be highly available and scalable. Network partitions may arise in those deployments and should be tolerated. One way of dealing with CAP constraints consists in relaxing consistency. Therefore, it is interesting to explore the set of consistency models not supported in an available and partition-tolerant service (CAP-constrained models). Other weaker consistency models could be maintained when scalable services are deployed in partitionable systems (CAP-free models). Three contributions arise: (1) multiple other CAP-constrained models are identified, (2) a borderline between CAP-constrained and CAP-free models is set, and (3) a hierarchy of consistency models depending on their strength and convergence is built.Muñoz-Escoí, FD.; Juan Marín, RD.; García Escriva, JR.; González De Mendívil Moreno, JR.; Bernabeu Aubán, JM. (2019). CAP Theorem: Revision of its related consistency models. The Computer Journal. 62(6):943-960. https://doi.org/10.1093/comjnl/bxy142S943960626Davidson, S. B., Garcia-Molina, H., & Skeen, D. (1985). Consistency in a partitioned network: a survey. ACM Computing Surveys, 17(3), 341-370. doi:10.1145/5505.5508Gilbert, S., & Lynch, N. (2002). Brewer’s conjecture and the feasibility of consistent, available, partition-tolerant web services. ACM SIGACT News, 33(2), 51-59. doi:10.1145/564585.564601Muñoz-Escoí, F. D., & Bernabéu-Aubán, J. M. (2016). A survey on elasticity management in PaaS systems. Computing, 99(7), 617-656. doi:10.1007/s00607-016-0507-8Brewer, E. (2012). CAP twelve years later: How the «rules» have changed. Computer, 45(2), 23-29. doi:10.1109/mc.2012.37Attiya, H., Ellen, F., & Morrison, A. (2017). Limitations of Highly-Available Eventually-Consistent Data Stores. IEEE Transactions on Parallel and Distributed Systems, 28(1), 141-155. doi:10.1109/tpds.2016.2556669Viotti, P., & Vukolić, M. (2016). Consistency in Non-Transactional Distributed Storage Systems. ACM Computing Surveys, 49(1), 1-34. doi:10.1145/2926965Burckhardt, S. (2014). Principles of Eventual Consistency. Foundations and Trends® in Programming Languages, 1(1-2), 1-150. doi:10.1561/2500000011Herlihy, M. P., & Wing, J. M. (1990). Linearizability: a correctness condition for concurrent objects. ACM Transactions on Programming Languages and Systems, 12(3), 463-492. doi:10.1145/78969.78972Lamport. (1979). How to Make a Multiprocessor Computer That Correctly Executes Multiprocess Programs. IEEE Transactions on Computers, C-28(9), 690-691. doi:10.1109/tc.1979.1675439Ladin, R., Liskov, B., Shrira, L., & Ghemawat, S. (1992). Providing high availability using lazy replication. ACM Transactions on Computer Systems, 10(4), 360-391. doi:10.1145/138873.138877Yu, H., & Vahdat, A. (2002). Design and evaluation of a conit-based continuous consistency model for replicated services. ACM Transactions on Computer Systems, 20(3), 239-282. doi:10.1145/566340.566342Curino, C., Jones, E., Zhang, Y., & Madden, S. (2010). Schism. Proceedings of the VLDB Endowment, 3(1-2), 48-57. doi:10.14778/1920841.1920853Das, S., Agrawal, D., & El Abbadi, A. (2013). ElasTraS. ACM Transactions on Database Systems, 38(1), 1-45. doi:10.1145/2445583.2445588Chen, Z., Yang, S., Tan, S., He, L., Yin, H., & Zhang, G. (2014). A new fragment re-allocation strategy for NoSQL database systems. Frontiers of Computer Science, 9(1), 111-127. doi:10.1007/s11704-014-3480-4Kamal, J., Murshed, M., & Buyya, R. (2016). Workload-aware incremental repartitioning of shared-nothing distributed databases for scalable OLTP applications. Future Generation Computer Systems, 56, 421-435. doi:10.1016/j.future.2015.09.024Elghamrawy, S. M., & Hassanien, A. E. (2017). A partitioning framework for Cassandra NoSQL database using Rendezvous hashing. The Journal of Supercomputing, 73(10), 4444-4465. doi:10.1007/s11227-017-2027-5Muñoz-Escoí, F. D., García-Escrivá, J.-R., Sendra-Roig, J. S., Bernabéu-Aubán, J. M., & González de Mendívil, J. R. (2018). Eventual Consistency: Origin and Support. Computing and Informatics, 37(5), 1037-1072. doi:10.4149/cai_2018_5_1037Fischer, M. J., Lynch, N. A., & Paterson, M. S. (1985). Impossibility of distributed consensus with one faulty process. Journal of the ACM, 32(2), 374-382. doi:10.1145/3149.21412

Structural and vibrational study of Bi2Se3 under high pressure

The structural and vibrational properties of bismuth selenide (Bi2Se3) have been studied by means of x-ray diffraction and Raman scattering measurements up to 20 and 30 GPa, respectively. The measurements have been complemented with ab initio total-energy and lattice dynamics calculations. Our experimental results evidence a phase transition from the low-pressure rhombohedral (R-3m) phase (B-Bi2Se3) with sixfold coordination for Bi to a monoclinic C2/m structure (B-Bi2Se3) with sevenfold coordination for Bi above 10 GPa. The equation of state and the pressure dependence of the lattice parameters and volume of a and B phases of Bi2Se3 are reported. Furthermore, the presence of a pressure-induced electronic topological phase transition in B-Bi2Se3 is discussed. Raman measurements evidence that Bi2Se3 undergoes two additional phase transitions around 20 and 28 GPa, likely toward a monoclinic C2/c and a disordered body-centered cubic structure with 8-fold and 9- or 10-fold coordination, respectively. These two high-pressure structures are the same as those recently found at high pressures in Bi2Te3 and Sb2Te3. On pressure release, Bi2Se3 reverts to the original rhombohedral phase after considerable hysteresis. Symmetries, frequencies, and pressure coefficients of the Raman and infrared modes in the different phases are reported and discussed.This work was done under financial support from Spanish Ministry of Science and Innovation under Projects No. MAT2007-66129, No. MAT2010-21270-C04-03/04, and No. CSD-2007-00045 and from the Valencian government under Project No. Prometeo/2011-035. It is also supported by the Ministry of Education, Youth and Sports of the Czech Republic Project No. MSM 0021627501

High-pressure vibrational and optical study of Bi2Te3

We report an experimental and theoretical lattice dynamics study of bismuth telluride (Bi2Te3) up to 23 GPa together with an experimental and theoretical study of the optical absorption and reflection up to 10 GPa. The indirect bandgap of the low-pressure rhombohedral (R-3m) phase (α-Bi2Te3) was observed to decrease with pressure at a rate of −6 meV/GPa. In regard to lattice dynamics, Raman-active modes of α-Bi2Te3 were observed up to 7.4 GPa. The pressure dependence of their frequency and width provides evidence of the presence of an electronic-topological transition around 4.0 GPa. Above 7.4 GPa a phase transition is detected to the C2/m structure. On further increasing pressure two additional phase transitions, attributed to the C2/c and disordered bcc (Im-3m) phases, have been observed near 15.5 and 21.6 GPa in good agreement with the structures recently observed by means of x-ray diffraction at high pressures in Bi2Te3. After release of pressure the sample reverts back to the original rhombohedral phase after considerable hysteresis. Raman- and IR-mode symmetries, frequencies, and pressure coefficients in the different phases are reported and discussed.This work has been done under financial support from Spanish MICINN under projects MAT2008-06873-C02- 02, MAT2007-66129, Prometeo/2011-035, MAT2010-21270-C04-03/04, and CSD2007-00045 and supported by the Ministry of Education, Youth and Sports of the Czech Republic (MSM 0021627501)

HST/WFPC2 imaging of the circumnuclear structure of LLAGNs. I Data and nuclear morphology

To advance our knowledge of the nature of the central source in LLAGNs and its relation with stellar clusters, we are carrying out several imaging projects with HST at near-UV, optical and near-IR wavelengths. In this paper, we present the first results obtained with observations of the central regions of 57 LLAGNs imaged with the WFPC2 through any of the V (F555W, F547M, F614W) and I (F791W, F814W) filters that are available in the HST archive. The sample contains 34% of the LINERs and 36% of the TOs in the Palomar sample. The mean spatial resolution of these images is 10 pc. With these data we have built an atlas that includes structural maps for all the galaxies, useful to identify compact nuclear sources and, additionally, to characterize the circumnuclear environment of LLAGNs, determining the frequency of dust and its morphology. The main results obtained are: 1) We have not found any correlation between the presence of nuclear compact sources and emission-line type. Thus, nucleated LINERs are as frequent as nucleated TOs. 2) The nuclei of "Young-TOs" are brighter than the nuclei of "Old-TOs" and LINERs. These results confirm our previous results that Young-TOs are separated from other LLAGNs classes in terms of their central stellar population properties and brightness. 3) Circumnuclear dust is detected in 88% of the LLAGNs, being almost ubiquitous in TOs. 4) The dust morphology is complex and varied, from nuclear spiral lanes to chaotic filaments and nuclear disk-like structures. Chaotic filaments are as frequent as dust spirals; but nuclear disks are mainly seen in LINERs. These results suggest an evolutionary sequence of the dust in LLAGNs, LINERs being the more evolved systems and Young-TOs the youngest. The full collection of figures are at http://www.iaa.es/~rosa/research/LLAGNs2007/LLAGNs-HSTIma1.htmlComment: Paper accepted in AJ, pdf file and the full collection of figures are at the ULR: http://www.iaa.es/~rosa/research/LLAGNs2007/LLAGNs-HSTIma1.htm

Claiming the patrimonial value of the agrarian. Sugar cane in oriental Malaga

En el ámbito de protección del patrimonio, cada vez existen más autores y trabajos que inciden en la necesidad y la importancia de no concebir aisladamente los testigos inmuebles, muebles y territoriales de una determinada actividad a la hora de aplicarle una protección, pues los unos sin los otros no tienen razón de ser. En la industria de la caña de azúcar esta protección podría en muchos casos incluir el suelo agrario y fuente de materia prima que hizo funcionar dicha industria. De esta forma, la protección tendría efecto por igual sobre los elementos inmuebles (arquitectura), muebles (maquinaria y herramientas) y el territorio (suelo agrario donde se cultivaba la caña que suministraba la fábrica). El trabajo que se presenta a continuación se centra en la importancia de esta coexistencia entre fábrica-maquinariasuelo agrario. El estudio se focaliza en una de las fábricas existentes en el litoral este malagueño cuya situación en la actualidad se torna un tanto confusa debida a la ambigüedad de la norma aplicable. Por este motivo, se investiga la evolución del parcelario agrario en el entorno de la fábrica, así como el marco legislativo que da lugar al grado de protección actual ya que podría verse afectado por diversas actividades proyectadas en el municipio a corto-medio plazo. Se plantea una reflexión sobre la forma de proceder a la hora de proteger el patrimonio agrario en general, y más concretamente aquel vinculado a ciertas industrias que dejaron una profunda huella en el territorio de la Axarquía y sus habitantes.In the field of heritage protection, more and more authors and research emphasize the need and importance of not considering the immovable, movable and territorial testimonies of a certain activity independently when deciding the protection they deserve, since one without the other have no reason to exist. In the sugar cane industry, this protection could in many cases include the agricultural land which was the main source of raw material to such industry. This way, the protection would have an equal effect on the immovable elements (architecture), movable (machinery and tools), and the territory (lands where the canes were grown to supply the factory). The following work stresses on the significance of this coexistence between Factory-machinery- agricultural land. The study focusses on one of the existing factories on the east coast of Malaga, show current situation is somewhat confusing due to the ambiguity of the applicable regulations. For this reason, the evolution of the agricultural land in the area that surrounds the factory is throughtfully studied together with the legislative framework that gives rise to the current degree of protection, since this could be affected by various activities that are planned in the shortmedium term in the town. A reflection on how to proceed when it comes to protecting agricultural heritage in general, and more specifically that linked to certain industries that imprinted a deep agrarian character into the ‘Axarquia’ territory and its inhabitants

The Starburst-AGN connection: The role of stellar clusters in AGNs

Nuclear stellar clusters are a common phenomenon in spirals and in starbursts galaxies, and they may be a natural consequence of the star formation processes in the central regions of galaxies. HST UV imaging of a few Seyfert 2 galaxies have resolved nuclear starbursts in Seyfert 2 revealing stellar clusters as the main building blocks of the extended emission. However, we do not know whether stellar clusters are always associated with all types of nuclear activity. We present NUV and optical images provided by HST to find out the role that stellar clusters play in different types of AGNs (Seyferts and LLAGNs). Also with these images, we study the circumnuclear dust morphology as a probe of the circumnuclear environment of AGNs. Here we present a summary of the the first results obtained for the sample of Seyferts and LLAGN galaxies.Comment: Contribution to the conference proceedings "Space Astronomy: The UV window to the Universe", El Escorial (Spain), May 28-June 1 2007, submitted to Ap&SS, invited ed. Gomes de Castro, A.I. Further explanations are in Mu\~noz Marin, et al (2007) and Gonzalez Delgado et al (2007); and the full collection of figures are at the ULR: http://www.iaa.es/~rosa/research/LLAGNs2007/LLAGNs-HSTIma1.html http://www.iaa.es/~manuel/publications/paper01.htm

Motivos de la práctica del pádel en relación a la edad, el nivel de juego y el género

The aim of this study was to determine the motivations that may explain the actual increment in padel practice through different socio-demographic parameters such as sex, age or category. A total of 77 participants (43male and 34female), completed a questionnaire addressing sociodemographic information and the "Measurement Scale Motives for Physical Activity-Revised (MPAM-R)". The results point outed enjoyment (6.07) as the most valued reason for practice. Other appreciated reasons were competition (5.43), fitness / health (5.49) and sociability (5.07), being appearance the least scored (3.97). Significant differences were observed between categories (p<0.05). Current data provide useful information to sports centres managers in designing action plans to improve the quality of services offered, as well as supporting the teaching and learning process in padel.El objetivo de este estudio fue determinar los motivos que han provocado el actual crecimiento en la práctica del pádel en diferentes parámetros sociodemográficos como el género, la edad, el tiempo de práctica y la categoría de juego. Un total de77 participantes (43 hombres y 34 mujeres) respondió a las preguntas de un cuestionario sociodemográfico y de la “Escala de Medida de los Motivos para la Actividad Física-Revisada (MPAM-R)”. Los resultados muestran que el motivo más valorado fue el disfrute (6.07) como causa principal de la práctica del pádel. Otros motivos también valorados han sido la competencia (5.43), el fitness/salud (5.49) y la sociabilidad (5.07), mientras que el menos valorado fue la apariencia (3.97). Se encontraron diferencias significativas en los motivos de práctica en función de la categoría de juego (p<0.05). Estos datos ofrecen información muy útil a la hora de diseñar planes de actuación que aumenten la calidad de servicios ofrecidos en los centros deportivos, así como para la mejora del proceso enseñanza-aprendizaje del pádel