Amalgamated products and properly 3-realizable groups

In this paper, we show that the class of all properly 3-realizable groups is closed under amalgamated free products (and HNN-extensions) over finite groups. We recall that $G$ is said to be properly 3-realizable if there exists a compact 2-polyhedron $K$ with $\pi_1(K) \cong G$ and whose universal cover $\tilde{K}$ has the proper homotopy type of a 3-manifold (with boundary).Comment: J. Pure Appl. Alg., to appea

Universal covers and 3-manifolds

AbstractIn this paper, we show that if a finitely presented group G is the fundamental group of a finite fake surface in which the link of any vertex is not homeomorphic to the 1-skeleton of a tetrahedron, then there is a finite 2-complex K with π1(K)≅G and whose universal cover K̃ has the proper homotopy type of a 3-manifold. As a consequence, the cohomology group H2(G;ZG) is free abelian

Weak Z\mathcal Z-structures and one-relator groups

Motivated by the notion of boundary for hyperbolic and $CAT(0)$ groups, M. Bestvina in "Local Homology Properties of Boundaries of Groups" introduced the notion of a (weak) $\mathcal Z$-structure and (weak) $\mathcal Z$-boundary for a group $G$ of type $\mathcal F$ (i.e., having a finite $K(G,1)$ complex), with implications concerning the Novikov conjecture for $G$. Since then, some classes of groups have been shown to admit a weak $\mathcal Z$-structure (see "Weak $\mathcal Z$-structures for some classes of groups" by C.R. Guilbault for example), but the question whether or not every group of type $\mathcal F$ admits such a structure remains open. In this paper, we show that every torsion free one-relator group admits a weak $\mathcal Z$-structure, by showing that they are all properly aspherical at infinity; moreover, in the $1$-ended case the corresponding weak $\mathcal Z$-boundary has the shape of either a circle or a Hawaiian earring depending on whether the group is a virtually surface group or not. Finally, we extend this result to a wider class of groups still satisfying a Freiheitssatz property

Advances in complex systems and their applications to cybersecurity

Cybersecurity is one of the fastest growing and largest technology sectors and is increasingly being recognized as one of the major issues in many industries, so companies are increasing their security budgets in order to guarantee the security of their processes. Successful menaces to the security of information systems could lead to safety, environmental, production, and quality problems. One of the most harmful issues of attacks and intrusions is the ever-changing nature of attack technologies and strategies, which increases the difficulty of protecting computer systems. As a result, advanced systems are required to deal with the ever-increasing complexity of attacks in order to protect systems and information

Base Case Analysis of a HYSOL Power Plant

Concentrating solar power (CSP) plants are regarded as an alternative solution for electricity generation. The main drawback of this technology is related to the intermittent and seasonal nature of the solar irradiation. As a consequence, most CSP plants have a reduced capacity factor and difficulties to supply electricity on demand to the grid. The integration of energy back-up systems may contribute to increasing power generation capacity and stability. Several options are being developed at present which are based on the incorporation of Thermal Energy Storage (TES) and also the use of auxiliary fuels. HYSOL is a new concept in CSP technology that relies on the integration of a molten salt TES system operating in hybrid mode with a biogas turbine with a Heat Recovery System (HRS). This paper illustrates the methodology and first results obtained during the development of the static model, considering a Base Case of HYSOL configuration. The study of this Base Case allows evaluating the impact of HYSOL technology, providing preliminary plant information and defining the required tools to be used in the project

Influencia del tratamiento «a fuego» en las características del estuco tradicional con cal

This research advances in the attempt to recover the traditional technique of stucco by fire; paradigm of indoor decoration until half of 20th century due to its high quality marbled imitations. On its implementation process, it was used lime mortars with marble aggregates, mineral pigments and greases. With these materials, masses were prepared and extended into the walls, they were painted in fresco and ended with the passage of a heated metal tool. As with any other technique, the time passing over has blurred the knowledge on the subject, making very difficult the preservation or restoration of examples in our heritage. Despite of the limited literature, the process has been recovered; subjecting the samples prepared at different trials that have characterized the finished, both in its merits and its conferred characteristics by finally protecting the samples with a layer of wax, as was done traditionally.Esta investigación avanza en el intento de recuperar la técnica tradicional del estuco a fuego, paradigma de la decoración de espacios interiores hasta la mitad del s. XX por sus imitaciones marmóreas de gran calidad. Para ejecutarlos se utilizaban morteros de cal con áridos de mármol, pigmentos minerales y grasas; con estos materiales se preparaban y tendían las masas, se pintaban al fresco y se terminaban con el paso de una herramienta metálica caliente. Como sucede con otras técnicas, el paso del tiempo ha difuminado los conocimientos sobre la materia, haciendo muy difícil la conservación o restauración de los ejemplos en nuestro patrimonio. A partir de la escasa bibliografía existente se ha recuperado el proceso, sometiendo las muestras elaboradas a diferentes ensayos que han caracterizado el acabado final, tanto en sus características intrínsecas como en las que le son conferidas al proteger finalmente las muestras con una capa de cera, tal y como se realizaba tradicionalmente

Modelo de argumentación técnica para el dictamen de patología de la edificación

In the field of construction, a technical pathology report is a document where a technical expert in this discipline makes known their technical opinion thereon to a layman who has no real understanding or to another expert with less knowledge. In order for the addressee to trust the technician’s opinion, it’s necessary to appreciate internal consistency and plausibility in the report, among other things. Scientific and technical knowledge, presupposed in the author is not enough because the best technical argumentation can not properly transmit its content. Therefore, it’s possible and necessary to introduce argument criteria, supplementary to purely technical ones, in order to improve transparency and comprehensibility in the report. For this reason, we are presenting a technical argumentation model, developed from others logic argument models, especially Toulmin’s one. It was exposed in 1979 and has been applied in very different fields, but not, unless we know, in building pathology.En el campo de la construcción, un dictamen de patología es un documento en el que un técnico experto en esta disciplina traslada su opinión técnica a un profano o a otro menos experto que él. Para que el destinatario confíe en la opinión del técnico, ha de apreciar coherencia interna y verosimilitud en el dictamen, entre otras cosas. Los conocimientos científicos y técnicos que se le presuponen al autor del dictamen no son suficientes, porque la mejor argumentación técnica puede no transmitir adecuadamente su contenido. Así, es posible y deseable utilizar criterios lógicos de argumentación complementarios a los puramente técnicos, para potenciar la transparencia y comprensibilidad del dictamen, para lo que presentamos un modelo de argumentación técnica desarrollado a partir de otros modelos de argumentación lógica, especialmente del expuesto por Stephen Toulmin en 1979, que se ha aplicado a diferentes campos, pero no, que sepamos, al de patología en edificación

Modelo matemático del comportamiento mecánico en flexión del cartón-yeso

The article proposes a mathematical model which predicts the bearing load capacity of gypsum plasterboard sheets in bending tests, based on the geometric dimensions and the mechanical properties of the constituent materials. Thus obtained values are compared with those proposed by various European and American Standards for the minimum bearing load capacity as well as with experimental laboratory measurements. In both cases the results obtained reached an excellent level of agreement.Se presenta un modelo matemático que predice la carga de rotura de las placas de cartón-yeso en ensayos a flexotracción, a partir del conocimiento de sus dimensiones geométricas y de las propiedades mecánicas de los materiales componentes. Los valores así obtenidos se comparan con los que proponen diversas normas europeas y americanas para la carga de rotura mínima, así como con medidas experimentales en laboratorio, obteniéndose en ambos casos un acuerdo excelente