Effect of freeze–thaw cycles on the void topologies and mechanical properties of asphalt

Frost and thawing damage asphalt in cold climates. Water that enters the pores of asphalt at low temperatures may accelerate its degradation. Water can expand into pores, altering the void content and shape, thus affecting the asphalt's internal structure and fracture properties. We can develop more durable asphalt types if we understand how void topology changes with freeze–thaw cycles. The purpose of this study is to establish a correlation between the mechanical properties of asphalts and the topological properties of voids. To determine their internal structure, various asphalt types representing dense asphalt and asphalt with voids were made and X-rayed before and after each freeze–thaw cycle. We also obtained the mechanical properties of asphalt and correlated them with the void properties. It was found that dense asphalt has the lowest degradation rate in wet conditions characterised by non-connected gaps, which was approximately constant with freeze–thaw cycles; however, dense asphalt was least durable under dry conditions compared with asphalts with more voids. Due to its high water retention rate, asphalt with a 10% void content degraded at an accelerated rate during the initial cycles. As a result of bigger voids, asphalt with a higher pore content plateaued in later cycles due to reduced water retention. This study demonstrates that the internal void topology affects the mechanical properties of asphalt during freeze–thaw cycles. These results can be used to understand changes in asphalt mechanical losses resulting from freeze-thaw cycles and to validate numerical models to perform parametric studies of the asphalt's freeze–thaw degradation

Isometries of Almost-Riemannian structures on nonnilpotent, solvable 3D Lie groups

In this paper we prove that automorphisms are the only isometries between rank two Almost-Riemannian Structures on the class of nonnilpotent, solvable, connected 3D Lie groups. As a consequence, a classification result for rank two ARSs on the groups in question is obtained.Comment: arXiv admin note: substantial text overlap with arXiv:2201.0641

Obtaining preforms by additive fused deposition modelling (FDM) extrusion technology for the manufacture of high-performance composites

The composites industry is present in practically all industrial sectors with an annual growth rate of 5%. Its contribution to the priority "light-weighting" driver in the transport sector is key. The efficiency of the industry is made possible by the evolution of manufacturing processes that also improve the performance of the products obtained. For example, out-of-autoclave (OOA) processes can obtain high-performance composites such as those obtained by the autoclave process at lower costs. A key aspect in the development of this type of process is the preforming of continuous fibre reinforcements, which can achieve high fibre percentages while facilitating processing. Manufacturing these preforms currently requires multiple steps, equipment and tooling. TECNALIA's work developing the ADDICOMP technology, an alternative preform manufacturing method using an additive process based on Fused Deposition Modelling (FDM) is detailed in this article. This development is patented by Tecnalia and was conducted in 2 phases: (a) development of continuous fibre filaments coated with polymeric material and printable by FDM and (b) fine-tuning of FDM technology to print filaments with a very high content of continuous fibre

Simulation of fuel particles motion in a 2D fluidized bed using a hybrid-model considering wall friction

The mixing of fuel particles is a key issue on the performance of fluidized bed reactors. In this work, the motion of a non-reactive fuel particle in a 2D bubbling fluidized bed at ambient conditions is simulated employing a hybrid-model. The hybrid-model, implemented in the code MFIX, simulates the dense and gas phases using a Two-Fluid Model (TFM) while the fuel particles are modeled using a Discrete Element Method (DEM). The importance of the present hybrid-model is that the interaction of the continuum phases with the fuel particles behavior is fully coupled. In a previous study, Hernández-Jiménez et al. (1) compared the fuel particles motion obtained from the simulation with experimental results measured in a cold 2D fluidized bed by Soria-Verdugo et al. (2, 3). The simulation results related to the location of the fuel particle in the bed were similar to the experimental data (Figure-1). Nevertheless, some discrepancies were found in important parameters such as the circulation time of the fuel particles. These discrepancies were associated to the overprediction of the simulated solids velocity. In the present work, in order to improve the accuracy of the simulated fuel particle motion in a bubbling fluidized bed, a friction term accounting for the effect of the walls of the bed on the continuum solid phase is introduced in the hybrid-model, as proposed by Hernández-Jiménez et al. (4). According to the results, prediction of the fuel circulation time is clearly improved when the friction term is included in the simulation (Figure-2). REFERENCES Hernández-Jiménez F. , Garcia-Gutierrez L.M., Soria-Verdugo A., Acosta-Iborra A. 2015. Fully coupled TFM-DEM simulations to study the motion of fuel particles in a fluidized bed, Chem. Eng. Sci.,134, 29, 57-66. Soria-Verdugo, A., Garcia-Gutierrez, L.M., Sánchez-Delgado, S., Ruiz-Rivas,U., 2011a. Circulation of an object immersed in a bubbling fluidized bed. Chem. Eng. Sci. 66, 78–87. Soria-Verdugo, A., Garcia-Gutierrez, L.M., García-Hernando, N., Ruiz-Rivas, U., 2011b. Buoyancy effects on objects moving in a bubbling fluidized bed. Chem. Eng. Sci.66, 2833–2841. Hernández-Jiménez, F., Cano-Pleite, E., Sánchez-Prieto, J., Garcia-Gutierrez, L.M., Acosta-Iborra, A. Development of an empirical wall-friction model for 2D simulations of pseudo-2D fluidized beds. Submitted for publication. Please click Additional Files below to see the full abstract

Divisibility networks of the rational numbers in the unit interval

[EN] Divisibility networks of natural numbers present a scale-free distribution as many other process in real life due to human interventions. This was quite unexpected since it is hard to find patterns concerning anything related with prime numbers. However, it is by now unclear if this behavior can also be found in other networks of mathematical nature. Even more, it was yet unknown if such patterns are present in other divisibility networks. We study networks of rational numbers in the unit interval where the edges are defined via the divisibility relation. Since we are dealing with infinite sets, we need to define an increasing covering of subnetworks. This requires an order of the numbers different from the canonical one. Therefore, we propose the construction of four different orders of the rational numbers in the unit interval inspired in Cantor's diagonal argument. We motivate why these orders are chosen and we compare the topologies of the corresponding divisibility networks showing that all of them have a free-scale distribution. We also discuss which of the four networks should be more suitable for these analysesJAC was funded by MEC grant number MTM2016-75963-P. PASH acknowledges the support of MESCyT-RD, Casa Brugal, and Fundacion Proyecto Escuela Hoy Inc. for his PhD grants. MAGM acknowledges funding from the Spanish Ministry of Education and Vocational Training (MEFP) through the Beatriz Galindo program 2018 (BEAGAL18/00203) and Spanish Ministry MINECO FIDEUA PID2019-106901GB-I00/10.13039/501100011033.Solares-Hernández, PA.; Garcia March, MA.; Conejero, JA. (2020). Divisibility networks of the rational numbers in the unit interval. Symmetry (Basel). 12(11):1-12. https://doi.org/10.3390/sym12111879S112121

U B V R I Photometry of Stellar Structures throughout the Disk of the Barred Galaxy NGC 3367

We report new detailed surface U, B, V, R, and I photometry of 81 stellar structures in the disk of the barred galaxy NGC 3367. The images show many different structures indicating that star formation is going on in the most part of the disk. NGC 3367 is known to have a very high concentration of molecular gas distribution in the central regions of the galaxy and bipolar synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a triple structure similar to a radio galaxy. We have determined the U, B, V, R, and I magnitudes and U - B, B - V, U - V, and V - I colors for the central region (nucleus), a region which includes supernovae 2003 AA, and 79 star associations throughout NGC 3367. Estimation of ages of star associations is very difficult due to several factors, among them: filling factor, metallicity, spatial distribution of each structure and the fact that we estimated the magnitudes with a circular aperture of 16 pixels in diameter, equivalent to $6''.8\sim1.4$ kpc. However, if the colors derived for NGC 3367 were similar to the colors expected of star clusters with theoretical evolutionary star tracks developed for the LMC and had a similar metallicity, NGC 3367 show 51 percent of the observed structures with age type SWB I (few tens of Myrs), with seven sources outside the bright surface brightness visible disk of NGC 3367.Comment: Accepted for publication (abr 2007) in The Astronomical Journal (July 2007 issue

Biogeomorphological processes in an arid transgressive dunefield as indicators of human impact by urbanization

This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. This author accepted manuscript is made available following 24 month embargo from date of publication (August 2018) in accordance with the publisher’s archiving policyUrban and tourist developments can have long-lasting impacts on coastal environments and fundamentally alter the evolution of coastal dune systems. This is the case of the Maspalomas dunefield (Gran Canaria, Canary Islands), hosting one of the largest tourist resorts in Spain. The resort was built on top of a sedimentary terrace at 25 m above sea level (El Inglés) in the 1960s, and has subsequently affected local winds and therefore aeolian sediment transport patterns. Buildings on the terrace deflect the winds to the south of the dunefield, where the rate of sediment transport accelerated. A shadow zone appeared to the lee side of the resort with a consequent decrease in wind speed and aeolian sediment transport and an increase in vegetation cover. In this paper, first we characterize the environmental changes around El Inglés terrace in recent decades, and describe the changes in the shadow zone through an analysis of the evolution of sedimentary volumes and vegetation characteristics (density, spatial patterns, and plants communities). A series of historical aerial photographs, recent orthophotos and digital elevation models obtained by digital photogrammetry and LiDAR, as well as fieldwork were used to characterize plant communities and spatial-temporal changes in erosive landforms. Results show changes in the pattern and migration rates of dunes located at the southern edge of the urbanization, as well as the formation of blowouts and large deflation areas, where the vegetation increases in density and number of plant communities. We discuss eco-anthropogenic factors that have produced these environmental changes.This work is a contribution of projects CSO2013-43256-R and CSO2016-79673-R (National R & D & I Plan) co-financed with ERDF funds and a PhD contract of the Canary Islands Agency for Research, Innovation and Information Society and by the European Social Fund (ESF)

Effect of the thermal treatment on the chemical components, sorption, and shrinkage properties of Tectona grandis juvenile wood

The effect of thermal treatment on the chemical components, equilibrium moisture content (EMC), and shrinkage of teak juvenile wood was studied. Heartwood and sapwood samples were thermally-treated at 180 ºC and 200 ºC. Extractive, Klason lignin, holocellulose, and α-cellulose contents, as well as pH on untreated and thermally-treated woods, were determined. The EMC was reached at five relative humidity (RH) levels using saturated salt solutions: 86 % (KCl), 76 % (NaCl), 58 % (NaBr), 33 % (MgCl2), and 0 % (P2O5). Linear and volumetric shrinkages were calculated for all EMCs. The ratio of sorption (S), coefficient of shrinkage (h), and fiber saturation point (FSP) were also determined. Thermally-treated wood exhibited lower holocellulose and α-cellulose contents than untreated wood and increased acidity due to degradation of the hemicelluloses. The thermal treatment reduced the EMC of heartwood and sapwood. However, sapwood was more sensitive to RH variations than heartwood regardless of the treatment. Thermally-treated woods had higher hygroscopic and dimensional stabilities, and lower FSP than untreated wood. The thermal treatment did not affect radial shrinkage of the heartwood between 33 % and 86 % RH. Heartwood was more sensitive to the effect of the thermal treatment on shrinkage and degradation of cell wall polymers compared to sapwood

Is DNA Damage Response Ready for Action Anywhere?

Organisms are continuously exposed to DNA damaging agents, consequently, cells have developed an intricate system known as the DNA damage response (DDR) in order to detect and repair DNA lesions. This response has to be rapid and accurate in order to keep genome integrity. It has been observed that the condensation state of chromatin hinders a proper DDR. However, the condensation state of chromatin is not the only barrier to DDR. In this review, we have collected data regarding the presence of DDR factors on micronuclear DNA lesions that indicate that micronuclei are almost incapable of generating an effective DDR because of defects in their nuclear envelope. Finally, considering the recent observations about the reincorporation of micronuclei to the main bulk of chromosomes, we suggest that, under certain circumstances, micronuclei carrying DNA damage might be a source of chromosome instability