Effective medium electrical response model of carbon nanotubes cement-based composites

The electrical properties of carbon nanotubes (CNT) cement-based composites have been modeled in previous works by circuit models or homogenization theories. An alternative approach is the use of an effective medium theory with induced polarization: In this work, a new model based on the generalized effective medium theory of induced polarization (GEMTIP) with cylindrical inclusions is proposed. The presented results and discussion show its applicability to interpret the electrical impedance spectra of cylindrical cement samples doped with multi-walled CNTs (MWCNTs). The MWCNTs were dispersed in different media: one nonionic surfactant, two superplasticizers, a cationic type polycarboxylate ether, and an anionic type naphthalene sulfonate. Particle dispersion and their sizes were analyzed by Ultraviolet–Visible (UV–Vis) spectroscopy, and Scanning Electron Microscopy (SEM) measurements. Two electrode electrical impedance spectra were measured and analyzed by circuital models and the proposed GEMTIP model. The results demonstrate the efficiency of the proposed model in describing the Alternating Current (AC) response of cement/CNT composites irrespective of the dispersant agent used to elaborate the samples.CBUAConsejería de Transformación Económica, Conocimiento, Empresas Universidades de la Junta de Andalucía P18-RT-3128MinCiencias 82779Piezoresistividad en Pasta de Cemento con Adición de Nanopartículas de Oro o Materiales CarbonososUniversidad de GranadaInstituto Colombiano de Crédito Educativo y Estudios Técnicos en el Exterio

Cement-Based Piezoelectricity Application: A Theoretical Approach

The linear theory of piezoelectricity has widely been used to evaluate the material constants of single crystals and ceramics, but what happens with amorphous structures that exhibit piezoelectric properties such as cement-based? In this chapter, we correlate the theoretical and experimental piezoelectric parameters for small deformations after compressive stress–strain, open circuit potential, and impedance spectroscopy on cement-based. Here, in detail, we introduce the theory of piezoelectricity for large deformations without including a functional for the energy; also, we show two generating equations in terms of a free energy’s function for later it will be reduced to constitutional equations of piezoelectricity for infinitesimal deformations. Finally, here is shown piezoelectric and electrical parameters of gold nanoparticles mixed to cement paste: the axial elasticity parameter Y=323.5±75.3kN/m2, the electroelastic parameter γ=−20.5±6.9mV/kN, and dielectric constant ε=939.6±82.9ε0F/m, which have an interpretation as linear theory parameters sijklD, gkij and εikT discussed in the chapter

Piezoelectric composite cements: Towards the development of self-powered and self-diagnostic materials

Piezoresistivity is the most commonly used sensing principle in cement-based smart composites for strainmonitoring applications. Nonetheless, the need for external electric power to conduct electrical resistivity measurements restricts the scalability of this technology, especially when implemented in remote structures. To address this issue, this manuscript thoroughly analyses the piezoelectric properties of cement composites doped with reduced graphene oxide (rGO) and evaluates their potential as self-powered strain sensors. To do so, a comprehensive methodology involving voltammetry measurements, open circuit potential determination, and uniaxial compression testing is developed to determine the piezoelectric coefficients of charge �33 and voltage �33. Furthermore, a novel circuital model for signal processing of the electromechanical response is developed and experimentally validated in terms of time series of output voltage, resistance, and the generated electric power. The developed methodology is applied to laboratory samples manufactured following two different filler dispersion methods. The presented results evidence that samples prepared by ultrasonic cleaner dispersion achieve optimal properties, with a piezoelectric charge coefficient of 1122.28 ± 246.67 pC/N, about 47 times greater than previously reported composites in the literature. Unlike piezoresistive cement-based composites, a remarkable nonlinear correlation between the fractional change in the intrinsic resistance of the material and the applied mechanical strain has been observed. Instead, a considerable linearity (R 2 = 0.96) between the externally applied mechanical strain and the generated (piezoelectric) electric power has been found, which suggests the great potential of the latter for conducting off-the-grid strain monitoring applications

Pypiezo-GO: A software tool for processing electromechanical measurements of piezoelectric reduced graphene oxide-cement composites

Self-diagnostic composites have become increasingly popular for structural health monitoring due to their ability to develop load-bearing strain sensors. Piezoelectric cement composites, in particular, represent an emerging area of research with vast potential for developing innovative self-powered or ultra-low power consumption sensors. In this context, this paper presents Pypiezo-GO, a software tool designed for the electromechanical characterization of reduced graphene oxide (rGO)-cement composites. The software tool, developed as an online cloud computing platform, accesses a database organized into DataFrame structures. The database contains the measurements from a set of experiments conducted on rGO-cement samples, including open circuit potential, cyclic voltammetry, and compressive testing. On this basis, Pypiezo-GO allows extracting the electrical properties of the samples, including their capacitance and piezoelectric factors. Furthermore, the platform enables the comparison of experimental time series with numerical predictions from a lumped circuit model implemented in MATLAB/Simulink, which is also included in this contribution. The presented software code is intended to represent a valuable tool for the development of new piezoelectric cement composites for strain self-sensing applications

Method for fabricating self-powered cement sensors based on gold nanoparticles

Nowadays, cement industry researchers are working hard to develop cement sensors based on nanocomposites because they can be used to develop intelligent and sustainable civil structures, self-powered, self-healing, or self-monitoring. In this light, this paper shows a methodology to obtain piezoelectric cement sensors, which produce enough energy not to require an external power source in sensing-strain applications. Mainly, two proposed experimental procedures increased the piezoelectric properties of these cement-based composites: add gold nanoparticles in the proper concentrations and apply a constant electric field during the curing stage. Firstly, the gold nanoparticles were obtained through a pulsed laser ablation system, and their particle size distribution was measured with a particle analyzer Litesizer 500 from Anton Paar, and their morphology was corroborated using a scanning electron microscope. Two concentrations (442 ppm and 658 ppm) of gold nanoparticles were obtained by changing the total ablation time. Next, we fabricated the cement sensors as described by ASTM standards C39-C39M. Hence, the cement was hand mixed with a water-to-cement ratio (w/c) of 0.47 for then poured on cylindrical molds saving the proportions recommended by the ASTM standard; in this stage, the gold nanoparticles were already part of the water ratio. Then, the cement sensors were cured under an external electric field and dried for 24 hours more in an oven to be finally ready for electromechanical characterization. Meanwhile, the electric response in altern current and the piezoelectric behavior were corroborated through electrical impedance spectroscopy and open circuit potential measurements, respectively. The piezoelectric behavior was obtained when a compressive strength was applied to the sensor, and the generated voltage was simultaneously measured. Finally, the electrical and mechanical characterization measurements were processed and analyzed using Python scripts. • The particle size and the families amount of Au NPs are affected by the ablation time. • The correct proportion of Au NPs increases the inherent piezoelectricity of cement paste. • The piezoelectric response can be addressed by coupling electric and mechanical tests

Diagnóstico y erradicación de la violencia - grupo violencia

IP 0101-10-001-87cotidiano, lo social y lo politico / Olga Amparo Sanchez,MarthaLucia Uribe -- La familia y la socializacion;de la violencia / Maria Himelda Ramirez -- Violencia y mediosdecomunicacion / Ramon Jimeno, Ana Maria Cano; Violencia y medios de comunicacion / Arturo Guerrero --Violencia y medios de comunicacion Guillermo Callej;M.;carcelaria en Colombia / Annette Pearson, Jesus Antonio Muñoz--Violenciaintrafamiliar : una mirada desde lo;Cauca : la violencia en el cauca vision sintetica -- Economiade la violencia / Salomon Kalmanovitz -- La;violencia y el problema agrario / Alejandro Reyes Posada -'- Reforma politica y proceso de paz / Alvaro;Echeverry Uruburu -- La violencia y los pueblos indigenasde hoy/ VictorManuel Bonilla S. -- Administracion;de justicia y nuevo codigo penal / Humberto Rendon Arango'-- Politica internacional y pacificacion nacional /;Juan Tokatlian, Rodrigo Pardo -- La crisis de la justiciay lasacciones requeridas para su transformacion /;Jorge Acevedo B. -- El aumento de la violencia delincuencial estambien una expresion de la crisis del derecho;penal / Pastor Alberto Acevedo -- Investigacion criminologica:homicidiosen Cali 1980 - 1985 / Jaime Patiño;'-- organizaciones populares- civiles e institucionalizacion /Carlos Vicente de Roux -- La violencia;[et al.] -- Manifestaciones de violencia en la zona esmeraldifera y el occidente de Boyaca / Javier Guerrero;Baron -- Bases para un posible estatuto del indigena / AdolfoTriana Antorveza -- Violencia y Colonizacion /;Alfredo Molano -- El programa de inversiones del PNR y elPPAyla inversion publica en la actual coyuntura /;Alberto Corchuelo -- Inspecciones de policia / Luisa MargaritaH. de Yepes'-- Consejo Regional indigena del;LIBROS: Colombia : violencia y democracia informe presentado aMinisteriode Gobierno / Jaime Arocha R. ..

XX Semana de la Enseñanza de la Física

25 a 29 de septiembre de 2017Facultad de Ciencias y EducaciónProyecto Curricular de Licenciatura en FísicaUniversidad Distrital Francisco José de Calda

Revista Temas Agrarios Volumen 26; Suplemento 1 de 2021

1st International and 2nd National Symposium of Agronomic Sciences: The rebirth of the scientific discussion space for the Colombian Agro.1 Simposio Intenacional y 2 Nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano

Alirocumab and cardiovascular outcomes after acute coronary syndrome

BACKGROUN

Alirocumab and Cardiovascular Outcomes after Acute Coronary Syndrome

BACKGROUN