Development of approximating functions to model and predict the properties of fresh and hardened fly ash-based geopolymer concrete

The manuscript presented herein is based on the investigation of the mechanical properties of fly ash-based geopolymer concrete and their link to fly ash (FA) characteristics. A database of 32 FA samples was created. Each FA sample was analyzed in terms of chemical composition, crystallographic properties and particle size distribution. The mechanical performance of geopolymer concrete (GPC) made from each FA sample was evaluated in terms of density, setting time, compressive and flexural strength, static elastic modulus and Poisson\u27s ratio. It is worth mentioning that the author has already published preliminary results of this study (Diaz and Allouche, 2010; Diaz et al. 2010) in peer-reviewed journals. The database was randomly divided into two sets; one consisting of 24 FA samples for model building using linear regression and another consisting of eight FA samples for validation. The first set was analyzed to detect correlations between fly ash characteristics and mechanical properties of GPC. Correlations within the elastic modulus, the compressive and flexural strengths of GPC were also sought and correlations were developed. These equations were tested on the second set of eight FA samples that were not included during the model building process. The results show that the elastic modulus, as well as the compressive and flexural strengths of GPC can be predicted with reasonable accuracy by analyzing the chemical, physical and crystallographic properties of a given FA and following the steps presented in this study. Additionally, it was also found that the mechanical behavior of CPC is similar to that of ordinary Portland cement (OPC) concrete, suggesting that equations, akin to those given by the American Concrete Institute\u27s Building Code (ACI 318, 2008), could be applied for CPC to determine its flexural strength and static elastic modulus

Juegos para desarrollar la motricidad fina en la Educación Inicial

El siguiente trabajo de investigación monográfica “Juegos para desarrollar la motricidad fina en la educación inicial”, tiene como propósito que mediante el juego va a desarrollar las funciones motrices de los niños. La investigación incluye conocer la relación de las formas de los juegos para el desarrollo de la motricidad y atraer la atención de los niños, para brindarles enseñanza en su temprana edad de formación que es orientada a la motricidad fina. La motricidad fina es primordial dado que contribuye al progreso integral, proporcionando beneficios que estimula, así como las actividades de movimiento musculares que coadyuvan a que el niño sea más independiente para realizar actividades vinculadas al desarrollo de habilidades sociales. La investigación también nos dice que se tiene que aplicar los siete principios de la educación inicial, como es el principio de un buen estado de salud, de respeto, de seguridad, del juego libre, de la comunicación, de la autonomía y del movimiento

Analysis of the Machinability of Carbon Fiber Composite Materials in Function of Tool Wear and Cutting Parameters Using the Artificial Neural Network Approach

[EN] Local delamination is the most undesirable damage associated with drilling carbon fiber reinforced composite materials (CFRPs). This defect reduces the structural integrity of the material, which affects the residual strength of the assembled components. A positive correlation between delamination extension and thrust force during the drilling process is reported in literature. The abrasive effect of the carbon fibers modifies the geometry of the fresh tool, which increases the thrust force and, in consequence, the induced damage in the workpiece. Using a control system based on an artificial neural network (ANN), an analysis of the influence of the tool wear in the thrust force during the drilling of CFRP laminate to reduce the damage is developed. The spindle speed, feed rate, and drill point angle are also included as input parameters of the study. The training and testing of the ANN model are carried out with experimental drilling tests using uncoated carbide helicoidal tools. The data were trained using error-back propagation-training algorithm (EBPTA). The use of the neural network rapidly provides results of the thrust force evolution in function of the tool wear and cutting parameters. The obtained results can be used by the industry as a guide to control the impact of the wear of the tool in the quality of the finished workpiece.The Ministry of Economy and Competitiveness of Spain, projects DPI2017-89197-C2-1-R and DPI2017-89197-C2-2-R] and the Ministry of Science, Innovation and Universities, grant number [FJCI-2017-34910], funded this research.Feito-Sánchez, N.; Muñoz-Sánchez, A.; Diaz-Alvarez, A.; Loya, J. (2019). Analysis of the Machinability of Carbon Fiber Composite Materials in Function of Tool Wear and Cutting Parameters Using the Artificial Neural Network Approach. Materials. 12(17):1-13. https://doi.org/10.3390/ma12172747S1131217Huang, X. (2009). Fabrication and Properties of Carbon Fibers. Materials, 2(4), 2369-2403. doi:10.3390/ma2042369Yang, Y., Jiang, Y., Liang, H., Yin, X., & Huang, Y. (2019). Study on Tensile Properties of CFRP Plates under Elevated Temperature Exposure. Materials, 12(12), 1995. doi:10.3390/ma12121995Liu, D., Tang, Y., & Cong, W. L. (2012). A review of mechanical drilling for composite laminates. Composite Structures, 94(4), 1265-1279. doi:10.1016/j.compstruct.2011.11.024Hocheng, H., & Tsao, C. . (2003). Comprehensive analysis of delamination in drilling of composite materials with various drill bits. Journal of Materials Processing Technology, 140(1-3), 335-339. doi:10.1016/s0924-0136(03)00749-0Hocheng, H., & Tsao, C. C. (2006). Effects of special drill bits on drilling-induced delamination of composite materials. International Journal of Machine Tools and Manufacture, 46(12-13), 1403-1416. doi:10.1016/j.ijmachtools.2005.10.004Hocheng, H., & Tsao, C. C. (2005). The path towards delamination-free drilling of composite materials. Journal of Materials Processing Technology, 167(2-3), 251-264. doi:10.1016/j.jmatprotec.2005.06.039Davim, J. ., & Reis, P. (2003). Study of delamination in drilling carbon fiber reinforced plastics (CFRP) using design experiments. Composite Structures, 59(4), 481-487. doi:10.1016/s0263-8223(02)00257-xSardiñas, R. Q., Reis, P., & Davim, J. P. (2006). Multi-objective optimization of cutting parameters for drilling laminate composite materials by using genetic algorithms. Composites Science and Technology, 66(15), 3083-3088. doi:10.1016/j.compscitech.2006.05.003Fernandes, M., & Cook, C. (2006). Drilling of carbon composites using a one shot drill bit. Part I: Five stage representation of drilling and factors affecting maximum force and torque. International Journal of Machine Tools and Manufacture, 46(1), 70-75. doi:10.1016/j.ijmachtools.2005.03.015Fernandes, M., & Cook, C. (2006). Drilling of carbon composites using a one shot drill bit. Part II: empirical modeling of maximum thrust force. International Journal of Machine Tools and Manufacture, 46(1), 76-79. doi:10.1016/j.ijmachtools.2005.03.016Feito, N., Diaz-Álvarez, A., Cantero, J. L., Rodríguez-Millán, M., & Miguélez, H. (2015). Experimental analysis of special tool geometries when drilling woven and multidirectional CFRPs. Journal of Reinforced Plastics and Composites, 35(1), 33-55. doi:10.1177/0731684415612931Feito, N., Díaz-Álvarez, J., Díaz-Álvarez, A., Cantero, J., & Miguélez, M. (2014). Experimental Analysis of the Influence of Drill Point Angle and Wear on the Drilling of Woven CFRPs. Materials, 7(6), 4258-4271. doi:10.3390/ma7064258Iliescu, D., Gehin, D., Gutierrez, M. E., & Girot, F. (2010). Modeling and tool wear in drilling of CFRP. International Journal of Machine Tools and Manufacture, 50(2), 204-213. doi:10.1016/j.ijmachtools.2009.10.004Abrão, A. M., Rubio, J. C. C., Faria, P. E., & Davim, J. P. (2008). The effect of cutting tool geometry on thrust force and delamination when drilling glass fibre reinforced plastic composite. Materials & Design, 29(2), 508-513. doi:10.1016/j.matdes.2007.01.016Rawat, S., & Attia, H. (2009). Wear mechanisms and tool life management of WC–Co drills during dry high speed drilling of woven carbon fibre composites. Wear, 267(5-8), 1022-1030. doi:10.1016/j.wear.2009.01.031Fernández-Pérez, J., Cantero, J. L., Díaz-Álvarez, J., & Miguélez, M. H. (2017). Influence of cutting parameters on tool wear and hole quality in composite aerospace components drilling. Composite Structures, 178, 157-161. doi:10.1016/j.compstruct.2017.06.043Tsao, C. C., & Hocheng, H. (2007). Effect of tool wear on delamination in drilling composite materials. International Journal of Mechanical Sciences, 49(8), 983-988. doi:10.1016/j.ijmecsci.2007.01.001Chen, W.-C. (1997). Some experimental investigations in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates. International Journal of Machine Tools and Manufacture, 37(8), 1097-1108. doi:10.1016/s0890-6955(96)00095-8Murphy, C., Byrne, G., & Gilchrist, M. D. (2002). The performance of coated tungsten carbide drills when machining carbon fibre-reinforced epoxy composite materials. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 216(2), 143-152. doi:10.1243/0954405021519735Fernández-Pérez, J., Cantero, J., Díaz-Álvarez, J., & Miguélez, M. (2019). Hybrid Composite-Metal Stack Drilling with Different Minimum Quantity Lubrication Levels. Materials, 12(3), 448. doi:10.3390/ma12030448Tsao, C. ., & Hocheng, H. (2004). Taguchi analysis of delamination associated with various drill bits in drilling of composite material. International Journal of Machine Tools and Manufacture, 44(10), 1085-1090. doi:10.1016/j.ijmachtools.2004.02.019Palanikumar, K., Prakash, S., & Shanmugam, K. (2008). Evaluation of Delamination in Drilling GFRP Composites. Materials and Manufacturing Processes, 23(8), 858-864. doi:10.1080/10426910802385026Mohan, N. S., Kulkarni, S. M., & Ramachandra, A. (2007). Delamination analysis in drilling process of glass fiber reinforced plastic (GFRP) composite materials. Journal of Materials Processing Technology, 186(1-3), 265-271. doi:10.1016/j.jmatprotec.2006.12.043Srinivasa Rao, B., Rudramoorthy, R., Srinivas, S., & Nageswara Rao, B. (2008). Effect of drilling induced damage on notched tensile and pin bearing strengths of woven GFR-epoxy composites. Materials Science and Engineering: A, 472(1-2), 347-352. doi:10.1016/j.msea.2007.03.023Enemuoh, E. U., El-Gizawy, A. S., & Chukwujekwu Okafor, A. (2001). An approach for development of damage-free drilling of carbon fiber reinforced thermosets. International Journal of Machine Tools and Manufacture, 41(12), 1795-1814. doi:10.1016/s0890-6955(01)00035-9Saravanan, M., Ramalingam, D., Manikandan, G., & Kaarthikeyen, R. R. (2012). Multi Objective Optimization of Drilling Parameters Using Genetic Algorithm. Procedia Engineering, 38, 197-207. doi:10.1016/j.proeng.2012.06.027Feito, N., Milani, A. S., & Muñoz-Sánchez, A. (2015). Drilling optimization of woven CFRP laminates under different tool wear conditions: a multi-objective design of experiments approach. Structural and Multidisciplinary Optimization, 53(2), 239-251. doi:10.1007/s00158-015-1324-yKrishnaraj, V., Prabukarthi, A., Ramanathan, A., Elanghovan, N., Senthil Kumar, M., Zitoune, R., & Davim, J. P. (2012). Optimization of machining parameters at high speed drilling of carbon fiber reinforced plastic (CFRP) laminates. Composites Part B: Engineering, 43(4), 1791-1799. doi:10.1016/j.compositesb.2012.01.007Krishnamoorthy, A., Rajendra Boopathy, S., Palanikumar, K., & Paulo Davim, J. (2012). Application of grey fuzzy logic for the optimization of drilling parameters for CFRP composites with multiple performance characteristics. Measurement, 45(5), 1286-1296. doi:10.1016/j.measurement.2012.01.008Abhishek, K., Datta, S., & Mahapatra, S. S. (2014). Optimization of thrust, torque, entry, and exist delamination factor during drilling of CFRP composites. The International Journal of Advanced Manufacturing Technology, 76(1-4), 401-416. doi:10.1007/s00170-014-6199-3El Kadi, H. (2006). Modeling the mechanical behavior of fiber-reinforced polymeric composite materials using artificial neural networks—A review. Composite Structures, 73(1), 1-23. doi:10.1016/j.compstruct.2005.01.020Altinkok, N., & Koker, R. (2004). Neural network approach to prediction of bending strength and hardening behaviour of particulate reinforced (Al–Si–Mg)-aluminium matrix composites. Materials & Design, 25(7), 595-602. doi:10.1016/j.matdes.2004.02.014Karnik, S. R., Gaitonde, V. N., Rubio, J. C., Correia, A. E., Abrão, A. M., & Davim, J. P. (2008). Delamination analysis in high speed drilling of carbon fiber reinforced plastics (CFRP) using artificial neural network model. Materials & Design, 29(9), 1768-1776. doi:10.1016/j.matdes.2008.03.014Altinkok, N., & Koker, R. (2006). Modelling of the prediction of tensile and density properties in particle reinforced metal matrix composites by using neural networks. Materials & Design, 27(8), 625-631. doi:10.1016/j.matdes.2005.01.005Stone, R., & Krishnamurthy, K. (1996). A neural network thrust force controller to minimize delamination during drilling of graphite-epoxy laminates. International Journal of Machine Tools and Manufacture, 36(9), 985-1003. doi:10.1016/0890-6955(96)00013-2Kuo, C.-F. J., Chang, C.-D., Su, T.-L., & Fu, C.-T. (2008). Optimization of the Dyeing Process and Prediction of Quality Characteristics on Elastic Fiber Blending Fabrics. Polymer-Plastics Technology and Engineering, 47(7), 678-687. doi:10.1080/03602550802129569Chen, W.-C., Fu, G.-L., Tai, P.-H., & Deng, W.-J. (2009). Process parameter optimization for MIMO plastic injection molding via soft computing. Expert Systems with Applications, 36(2), 1114-1122. doi:10.1016/j.eswa.2007.10.020Ko, Y.-D., Moon, P., Kim, C. E., Ham, M.-H., Myoung, J.-M., & Yun, I. (2009). Modeling and optimization of the growth rate for ZnO thin films using neural networks and genetic algorithms. Expert Systems with Applications, 36(2), 4061-4066. doi:10.1016/j.eswa.2008.03.010Faraz, A., Biermann, D., & Weinert, K. (2009). Cutting edge rounding: An innovative tool wear criterion in drilling CFRP composite laminates. International Journal of Machine Tools and Manufacture, 49(15), 1185-1196. doi:10.1016/j.ijmachtools.2009.08.002Ashrafi, H. R., Jalal, M., & Garmsiri, K. (2010). Prediction of load–displacement curve of concrete reinforced by composite fibers (steel and polymeric) using artificial neural network. Expert Systems with Applications, 37(12), 7663-7668. doi:10.1016/j.eswa.2010.04.076Levenberg, K. (1944). A method for the solution of certain non-linear problems in least squares. Quarterly of Applied Mathematics, 2(2), 164-168. doi:10.1090/qam/10666Khashaba, U. A., El-Sonbaty, I. A., Selmy, A. I., & Megahed, A. A. (2010). Machinability analysis in drilling woven GFR/epoxy composites: Part II – Effect of drill wear. Composites Part A: Applied Science and Manufacturing, 41(9), 1130-1137. doi:10.1016/j.compositesa.2010.04.011Heisel, U., & Pfeifroth, T. (2012). 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Allopregnanolone preclinical acute pharmacokinetic and pharmacodynamic studies to predict tolerability and efficacy for Alzheimer's disease.

To develop allopregnanolone as a therapeutic for Alzheimer's disease, we investigated multiple formulations and routes of administration in translationally relevant animal models of both sexes. Subcutaneous, topical (transdermal and intranasal), intramuscular, and intravenous allopregnanolone were bolus-administered. Pharmacokinetic analyses of intravenous allopregnanolone in rabbit and mouse indicated that peak plasma and brain levels (3-fold brain/plasma ratios) at 5min were sufficient to activate neuroregenerative responses at sub-sedative doses. Slow-release subcutaneous suspension of allopregnanolone displayed 5-fold brain/plasma ratio at Cmax at 30min. At therapeutic doses by either subcutaneous or intravenous routes, allopregnanolone mouse plasma levels ranged between 34-51ng/ml by 30min, comparable to published endogenous human level in the third trimester of pregnancy. Exposure to subcutaneous, topical, intramuscular, and intravenous allopregnanolone, at safe and tolerable doses, increased hippocampal markers of neurogenesis including BrdU and PCNA in young 3xTgAD and aged wildtype mice. Intravenous allopregnanolone transiently and robustly phosphorylated CREB within 5min and increased levels of neuronal differentiation transcription factor NeuroD within 4h. Neurogenic efficacy was achieved with allopregnanolone brain exposure of 300-500hr*ng/g. Formulations were tested to determine the no observable adverse effect level (NOAEL) and maximally tolerated doses (MTD) in male and female rats by sedation behavior time course. Sex differences were apparent, males exhibited ≥40% more sedation time compared to females. Allopregnanolone formulated in sulfobutyl-ether-beta-cyclodextrin at optimized complexation ratio maximized allopregnanolone delivery and neurogenic efficacy. To establish the NOAEL and MTD for Allo-induced sedation using a once-per-week intravenous regenerative treatment regimen: In female rats the NOAEL was 0.5mg/kg and MTD 2mg/kg. The predicted MTD in human female is 0.37mg/kg. In male rats the NOAEL and MTD were less than those determined for female. Outcomes of these PK/PD studies predict a safe and efficacious dose range for initial clinical trials of allopregnanolone for Alzheimer's disease. These findings have translational relevance to multiple neurodegenerative conditions

Paleoseismology of a major crustal seismogenic source near Mexico City. The southern border of the Acambay Graben

The Trans-Mexican Volcanic Belt is an active continental volcanic arc related to subduction along the Middle America trench. It is characterized by intra-arc extension resulting into several major arc-parallel active fault systems and tectonic basins. The Acambay graben, one of the largest of these basins, is located near Mexico City, in the central part of this province. In 1912, a M 6.9 earthquake ruptured the surface along the northern border of the graben together with at least two other faults. In this paper, we analyze the paleoseismic history of the southern border of the Acambay Graben, with new observations made in one natural outcrop and four paleoseismological trenches excavated across branches of the Venta de Bravo Fault at the site where it overlaps with the Pastores Fault. We present evidence of at least two paleo-earthquakes that occurred between 12,190 +/- 175 and 5,822 +/- 87 cal year BP and between 647 +/- 77 and 250 cal year BP. On one of these branches, we estimate a minimum slip-rate value between 0.1 and 0.23 mm/year for the last 12 ka and a mean recurrence interval of 8.5 +/- 3 ka. By considering several likely rupture lengths along the Venta de Bravo and Pastores faults, we calculated a maximum possible magnitude of M-w 7.01 +/- 0.27. Finally, by correlating events recorded along different faults within the Acambay Graben, we discuss several possible rupture coalescent scenarios and related consequences for Mexico City

Análisis experimental y numérico del material compuesto de aramida frente a impacto balístico

Ponencia presentada en el XXII Congreso Nacional de Ingeniería Mecánica (CNIM 18) celebrado del 19 al 21 de septiembre de 2018 en Madrid.En este trabajo se ha realizado un estudio experimental y numérico del comportamiento mecánico un casco de combate frente a impacto balístico de projectiles esféricos de 1.7 gramos. Se ha desarrollado un modelo numérico que ha sido calibrado y validado mediante ensayos experimentales en placas de diferente espesor. Un vez validado el modelo, se han desarrollado los ensayos experimentales en el casco de combate. Entre las conclusiones de este trabajo destaca que localización del impacto en el casco influye notablemente en el límite balístico. Cabe destacar que el modelo numérico es capaz de reproducir cada capa del casco de combate lo cual puede ser beneficioso para llevar a cabo futuras investigaciones sobre el casco con aramida u otro material.Los autores agradecen al Ministerio de Economía y Competitividad de España y al programa FEDER del Proyecto RTC-2015-3887-8 y al Proyecto DPI2017-88166-R por el apoyo financiero de la obra

Investigation of engineering properties of normal and high strength fly ash based geopolymer and alkali-activated slag concrete compared to ordinary Portland cement concrete

Fly ash-based geopolymer (FAGP) and alkali-activated slag (AAS) concrete are produced by mixing alkaline solutions with aluminosilicate materials. As the FAGP and AAS concrete are free of Portland cement, they have a low carbon footprint and consume low energy during the production process. This paper compares the engineering properties of normal strength and high strength FAGP and AAS concrete with OPC concrete. The engineering properties considered in this study included workability, dry density, ultrasonic pulse velocity (UPV), compressive strength, indirect tensile strength, flexural strength, direct tensile strength, and stress-strain behaviour in compression and direct tension. Microstructural observations using scanning electronic microscopy (SEM) are also presented. It was found that the dry density and UPV of FAGP and AAS concrete were lower than those of OPC concrete of similar compressive strength. The tensile strength of FAGP and AAS concrete was comparable to the tensile strength of OPC concrete when the compressive strength of the concrete was about 35 MPa (normal strength concrete). However, the tensile strength of FAGP and AAS concrete was higher than the tensile strength of OPC concrete when the compressive strength of concrete was about 65 MPa (high strength concrete). The modulus of elasticity of FAGP and AAS concrete in compression and direct tension was lower than the modulus of elasticity of OPC concrete of similar compressive strength. The SEM results indicated that the microstructures of FAGP and AAS concrete were more compact and homogeneous than the microstructures of OPC concrete at 7 days, but less compact and homogeneous than the microstructures of OPC concrete at 28 days for the concrete of similar compressive strength

Flexural strength and elastic modulus of ambient-cured blended low-calcium fly ash geopolymer concrete

Fly ash geopolymer is an emerging alternative binder with low environmental impact and potential to enhance sustainability of concrete construction. Most previous works examined the properties of fly ash-based geopolymer concrete (GPC) subjected to curing at elevated temperature. To extend the use of GPC in cast-in-situ applications, this paper investigated the properties of blended low-calcium fly ash geopolymer concrete cured in ambient condition. Geopolymer concretes were produced using low-calcium fly ash with a small percentage of additive such as ground granulated blast furnace slag (GGBFS), ordinary Portland cement (OPC) or hydrated lime to enhance early age properties. Samples were cured in room environment (18–23 °C and 70 ± 10% relative humidity) until tested. The results show that, density of hardened GPC mixtures is similar to that of normal-weight OPC concrete. Inclusion of additives enhanced the mechanical strengths significantly as compared to control concrete. For similar compressive strength, flexural strength of ambient cured GPC was higher than that of OPC concrete. Modulus of elasticity of ambient cured GPC tend to be lower than that of OPC concrete of similar grade. Prediction of elastic modulus by Standards and empirical equations for OPC concrete were found not conservative for GPC. Thus, an equation for conservative prediction of elastic modulus of GPC is proposed

In situ effects of simulated overfishing and eutrophication on settlement of benthic coral reef invertebrates in the Central Red Sea

In the Central Red Sea, healthy coral reefs meet intense coastal development, but data on the effects of related stressors for reef functioning are lacking. This in situ study therefore investigated the independent and combined effects of simulated overfishing through predator/grazer exclusion and simulated eutrophication through fertilizer addition on settlement of reef associated invertebrates on light-exposed and -shaded tiles over 4 months. At the end of the study period invertebrates had almost exclusively colonized shaded tiles. Algae were superior settling competitors on light-exposed tiles. On the shaded tiles, simulated overfishing prevented settlement of hard corals, but significantly increased settlement of polychaetes, while simulated eutrophication only significantly decreased hard coral settlement relative to controls. The combined treatment significantly increased settlement of bryozoans and bivalves compared to controls and individual manipulations, but significantly decreased polychaetes compared to simulated overfishing. These results suggest settlement of polychaetes and hard corals as potential bioindicators for overfishing and eutrophication, respectively, and settlement of bivalves and bryozoans for a combination of both. Therefore, if the investigated stressors are not controlled, phase shifts from dominance by hard corals to that by other invertebrates may occur at shaded reef locations in the Central Red Sea