bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of correlation of compressive strength with maturity of concrete mixed with accelerator
Authors: Medrano C T , Peña-Rodríguez G , García-Páez I H
Published: November 2019

The compressive strength of concrete mixtures with accelerator additives designed for structural elements with strength of 5000 psi was correlated with the maturity index of concrete at an early age. The design of the mixture was made by adding the quantity of additives according to the specifications of the supplier. The maturity index was calculated using the thermal profile of the concrete dependent of the setting time, which was obtained through an automated adiabatic system. The number of thermal sensors required for temperature measurement dependent of setting time (1, 3, 7, 14 and 28 days) was determined by a factorial experimental design of two factors. The correlation coefficient was 0.96, so the logarithmic model adequately explains the variability of the compressive strength. The equation obtained was validated by means of the values of resistance to compression measured by the standard method for each age of the concrete; all values are within the calibration range of the resistances estimated by the maturity method.
Vitrification of the solid waste obtained from the vacuum crushing of fluorescent lamps: chemical analysis and determination of the chemical stability in water of the vitrified solids
Authors: Amaya-Manjarrés G , Jiménez-Martínez J , Delvasto P
Published: November 2019

This paper deals with the vitrification processing of the wastes of glass and phosphor powder obtained after the vacuum crushing of spent fluorescent lamps. Both materials were characterized by means of scanning electron microscopy and X-ray fluorescence chemical analysis. The vitrification tests were performed at 1,100°C and 20 wt % borax was added to the samples as fluxing aid. Four formulations (batches) of glasses were made, the first one consisted only of spent lamp glass, the second one of spent lamp glass plus borax, the third one was the same as the second, but incorporating 20% weight of spent phosphor powder. The fourth one, a control, was made combining soda-lime glass cullet and borax. All four batches were chemically analyzed by X-ray fluorescence and no Hg was found on them. Rare earth elements were detected in the third batch glass prepared. The chemical stability of all batches was tested by contacting tests of the glasses with distilled water. As indicative of the stability, pH and electrical conductivity of the supernatants was measured. It was found that the more stable glasses were those incorporating only borax and spent lamp glass.
Mechanical strength of experimental mortars for plastering with partial addition of fly ash and hydrated lime
Authors: Hurtado-Figueroa O , Vega-Vanegas EJ , Cárdenas-Gutiérrez JA
Published: November 2019

In order to highlight the implementation of fly ash and hydrated lime in replacement of a % of the weight of the cementitious material traditionally used for the elaboration of mortar mixtures, a conventional mixture was made for mortars where the materials that compose this type of mixtures were previously selected, analyzed and implemented. The evaluations of the materials were carried out under the standards indicated by the Norma Técnica Colombiana that guarantee the reliability of the resulting mixture. The fly ash that was used was obtained from the power plant Termotasajero of the Municipality of San Cayetano located in the department of north Santander-Colombia. The hydrated lime was obtained in the municipality of Malaga located in the department of Santander-Colombia. The experimental mixtures presented a replacement of 40%, 50%, 60% and 70% of the weight of the cementitious material traditionally used in the city. At the same time, 10%, 20% and 30% of hydrated lime was added to the experimental mixtures in relation to the weight of the added fly ash. With each one of the elaborated mixtures, both traditional and experimental, 3 cubes were made as indicated in the Norma Técnica Colombiana for this purpose. After the 21 days of its elaboration to each one of the cubes their resistance to compression was determined by means of their respective test in the ibertest machine property of the Francisco de Paula Santander university located in the city of San Jose de Cucuta-Colombia. The data obtained in the tests were compared determining the viability of the addition of fly ash and hydrated lime in the mixtures for paste mortar, with the incorporation of a %. additional water in their designs. Thus generating a positive environmental, social and economic impact through the final disposal and marketing of an industrial waste, fly ash, and the use of a natural material, hydrated lime, in mixtures with cementitious matrix for mortars.
Comparative study of the effect of the exchange-correlation functional on the structural and electronic properties of rutile
Authors: Bolívar Marín Y , Alcalá Varilla L A , González Ramirez I A
Published: November 2019

A comparative study is presented, based on density functional theory, of the influence that the different approximations of the exchange-correlation functional have on the structural and electronic properties of titanium dioxide in the rutile phase. In this work, the method of plane waves and pseudopotentials, as implemented in the Quantum Espresso package was used. The approximations to the exchange-correlation functional that were considered are the local density approximation, the generalized gradient approximation in the form of Perdew- Burke-Ernzerhof, the Perdew-Burke-Ernzerhof for solids, and the Perdew-Wang 91. For each case, the effects due to the inclusion of spin (spin polarization), and the correction of Hubbard (U = 4.2 eV for Ti) were also studied. We found that the Perdew-Burke-Ernzerhof for solids functional offers the best results for the calculation of the lattice parameters and bond lengths, followed by the Perdew-Burke-Ernzerhof and Perdew-Wang 91. For the bond angles, the best description was obtained with the Perdew-Burke-Ernzerhof and Perdew-Wang 91 approximations. The density analysis of states showed that the functional PW91 and PBE, better describe the band gap compared with the functional PBEsol and LDA when the Hubbard correction it is not been included, however, when this is included all the functional show the same deviation with respect to the experimental value (E
gap
= 3.0 eV). With and without the Hubbard correction (U = 4.2), all functionals underestimate the band gap.
Effect of expanded polystyrene waste in the creation of waterproofing paint
Authors: Bellon D , Zamudio W H , Tiria L C , Durán S M , Useche I E , Peña J
Published: November 2019

The production, use, and poor management of polymers, and especially of expanded polystyrene, have resulted in various environmental challenges, such as large-scale waste generation, accumulation of toxic substances, and the pollution of natural resources, chiefly of water and soil. Consequently, nations around the world are investing considerable research effort into developing waste treatment and reduction solutions. Some areas have even enacted bans against the use of the material, however, in the Colombian case, it continues to be highly represented in the industry, and given the low cost of this packaging, little effort has been made to find a replacement. Expanded polystyrene is a thermoplastic polymer with low weight, low thermal conductivity, low cost, and low water absorption; factors which have made it a less attractive target for recycling. It has, however, excellent resistance to mechanical compression, which makes it viable for study in other applications such as those considered in the present study, offering advantages in terms of environmental protection without the need to completely eliminate the use of the material. The present study analyses the effects of integrating waste expanded polystyrene into the process of creating waterproofing paint. The research is divided into three major phases: the first focusing on the determination of the paint’s technical requirements using previous research and by means of initial testing; the second, on elimination tests to validate the properties of various samples before preparing the final paint mixture; and finally, a third phase of final tests required for a waterproof paint. The final formula is applied to common materials in the construction sector, such as wood, metal, glass, and concrete, to validate each of the required properties. Among the main results, technical viability was identified in the second sample, which demonstrated the best results at a ratio of 1: 2.5: 2.5 of waste expanded polystyrene, D-limonene and methyl acetate, respectively.
Determination of the adequate dosage of the soil-cement, using clay of high plasticity
Authors: Rojas-Suárez J P , Orjuela-Abril M S , Prada-Botía G C
Published: November 2019

The clay is used in the area of constructions, ceramics and industrial applications: insecticides, pharmaceutical industry, cosmetics and painting, for its physical and chemical properties that are suitable for different civil projects (roads, public services network, constructions); the dosage is a technique to modify and improve the conditions of the soil-cement in reference to the resistance, conditions of insolubility, impermeability, durability and appearance. In this study, high plasticity clay was evaluated through different laboratory tests (humidity test, soil liquid limit, plasticity index, granulometric analysis, California Bearing Ratio) for three samples and specifying the methodology used in each step, with the objective of knowing its structure and functioning in rural roads in combination with soil-cement, looking for a more profitable and lasting option in this sector, in order to benefit the people surrounding these sectors, improving the income of the sector and seeking to mitigate the environmental impact.
Study of low plasticity clay for optimum dosage of the soil-cement
Authors: Rojas-Suárez J P , Orjuela-Abril M S , Prada-Botía G
Published: November 2019

The need to improve people’s living conditions starts from the reality of the durability of rural road constructions, which have a short useful life and have a negative impact on the inhabitants of these regions. This project aims to improve access to rural areas, rural economic development and thus improve the quality of life of people in the sector; taking into account that at the moment of building a rural road, has a better resistance and durability in time, this was done by analyzing the properties of the clay mixture of low plasticity in the dosage of soil-cement that were tested by tests to determine the liquid limit of soils, determination of the plastic limit, plasticity index, moisture test, classification of soil by sieving, granulometric analysis, unit weight-humidity relations in soils, soil support relationship in the laboratory; in order to find the best dosage that provides greater strength, long-term durability and risk reduction. The results indicate that this type of clay requires an improvement with cement, due to its bearing capacity of 2% and 4%, which gives it a very poor quality to be used in the construction of rural roads.
Comparative for obtaining the optimum dosage of the soil-cement in clays of high and low plasticity
Authors: Rojas Suárez J P , Orjuela Abril M S , Prada Botía G C
Published: November 2019

Dosage is a technique to modify and improve the conditions of the soil-cement that comply with the conditions of the “Instituto Nacional de Vías” standard and in the same way, is economic to be implemented in different types of clay. The clay was classified depending on its plasticity (high plasticity and low plasticity) and the behavior at loads; making laboratory tests of modified proctor, compaction and CBR% for the clays with 4% of soil cement; at the same time, the results of CBR% of soil cement of 4% with natural soils, of 6% of cement and 1 were compared. In this way, was made a proposal of the elaboration of each type of soil-cement with its respective percentage, concluding that the clay of high plasticity can be used for subgrade and the one of low plasticity has a weak bearing capacity.
Rheological, morphological, film and thermal properties of emulsions of polyvinyl acrylic resins, carboxymethyl cellulose and titanium oxide
Authors: Álvarez E , Murillo E A
Published: November 2019

The study of the physical-chemistry properties of dispersions are very importants in the coating industry, since of it depend the application and stability of these systems. Therefore, the aim of this investigation was evaluated the influence of the dispersion rate and titanium dioxide content in the rheological (steady and dynamic analyses), colloidal, morphological, films, and thermal properties of waterborne dispersions based on polyvinyl acrylic resin, carboxymethyl cellulose and titanium oxide. In this work were used two proportions of titanium oxide (5.51 wt% and 10.44 wt%) and the following dispersion rates: 900 rpm, 1200 rpm, 1500 rpm and 1725 rpm. The materials were characterized by rheological, dynamic light scattering, scanning electronic microscopy, adherence, hardness, flexibility and thermogravimetric analyses.
A bibliometric analysis of possible alternatives to achieve the replacement of cellulose acetate in cigarette filters from agricultural residues
Authors: Pachón Colmenares M A , Orjuela Abril M S , Rojas Suárez J P
Published: November 2019

Polymers have become one of the most recognized materials in the industry, due to their good physical properties and the efficiency of their production process, in addition to the versatility and breadth of their fields of application in the aerospace, automotive, construction, textile and adhesive industries. In the case of cellulose acetate, it is used in a wide variety of everyday products such as photographic films, varnishes and cigarette filters, which makes it a factor that negatively affects the environment, since this material takes a long time to decompose and in the process contaminates the place where it is located with particles, on the other side are the agricultural residues that are manipulated in an inappropriate way, generating contamination in landfills and water sources, the following bibliometric analysis was carried out in order to provide a solution to the worrisome situation of this polymer contamination and the agricultural residues contamination, in order to encourage the development of studies focused on producing degradable materials. Therefore, this article presents a bibliometric analysis on the various alternatives to replace cellulose acetate, focusing on the collection methodology and comparison of studies with a tool known as HitsCite. The articles have been investigated by bibliometric, trend and cluster analysis in a sample of 361 articles. The research has been carried out in one of the most recognized databases such as web of science and has allowed to identify the main trends and dynamics of the scientific literature. This in order to mitigate the environmental problems that are present in our environment and being a starting point to support monetary studies that implement environmentally friendly materials, being a topic that can create a positive and innovating impact in the industries commercial sectors.
Characterization of the physical-mechanical and thermal behavior of a clay building unit designed with thermo-insulating attributes and a coffee cisco organic additive
Authors: Narváez-Ortega M S , Sánchez-Molina J , Díaz-Fuentes C X
Published: November 2019

This research is articulated from the clay framework as material wealth of the region of Norte de Santander, Colombia, and seeks to structure attributes of passive thermal cooling in a ceramic piece for low cost masonry type block cooked with physical, mechanical and thermals feasible characteristics for warm tropical weather conditions of 33 °C on average. This work is based on previous studies that explores the partitions structure morphology in Blocks H10 establishing a model of 6 horizontal cavities for low thermal conductivity and having oblique geometry partitions to interrupt heat conduction by direct thermal bridge inside of the constructive unit called Form-C, which is taken as the object of analysis, adding 5% organic coffee cisco additive in the 95% clay mixture to increase the porosity with a proportion that does not affect the deterioration of the mechanical properties and allow to optimize the thermal insulation capacity regarding to a traditional product. Methodologies: in the first phase, prototypes of Block H10 with Form-A are manufactured by extrusion at the laboratory level as a comparative witness of the properties of a standard piece and Form-C as a piece with thermo-insulating strategies to execute physical-ceramic, geometric evaluations of mechanical resistance and water absorption applying the Norma Técnica Colombiana 4017 for masonry units. In the second stage, simulations of temperature distribution and heat flow are prepared by finite element method in ANSYS R16 software to determine the incidence of the variables in the mixture on heat transfer. The results obtained from thermal simulations show an energy decrease of 1.5 °C on average in relation to Form-A. In conclusion, the use of agro industrial scraps and the implementation of passive design techniques in the ceramic piece generate added value in a product that can be industrialized with improvements in technological properties from a thermal efficiency perspective in construction ceramics.
Influence of water/cement ratio on mechanical strength of concrete with partial addition of fly ash and hydrated lime
Authors: Hurtado-Figueroa O , Echavarria-Paez FJ , Cárdenas-Gutiérrez JA
Published: November 2019

Three mixtures were made for conventional concrete with different additions of cement, 300 kg/m3, 350 kg/m3 and 400 kg/m3, being these the 3 designs of mixtures more used for the elaboration of simple concretes. For each of the conventional mixtures, the % of water used for mixing was varied, which constituted 60%, 65% and 70% of the weight of the cementitious material. These % were taken in gradual increase to the one traditionally used in each of the mixing designs made. The aggregates used were assigned by Transmateriales S.A, located in the city of San José de Cúcuta, Colombia. The analysis of the materials of the mixtures, were carried out under the standards of the “Normas Tecnicas Colombianas” and the Tests of the “Instituto Nacional de Vías”. 40% of the concrete mix cementitious material was replaced by fly ash and hydrated lime. In order to determine the mechanical behavior of the mixtures resulting from partial addiction. The ash was collected from the thermoelectric Termotasajero S.A, located in the city of San José de Cúcuta, Colombia. The hydrated lime was recovered from the municipality of Malaga located in the department of Santander, Colombia. Of the % of cementitious material replaced, 30% corresponded to lime and 70% to ash, as an experimental basis for the production of unconventional mixtures. Having the % of cementitious material to replace and the % of substitute material, 3 designs of experimental mixtures were made taking as base each one of the designs of conventional mixtures made, with equal % of water for its mixing. Twenty-seven cylinders were manufactured for the experimental mixtures and the same number for conventional mixtures, a figure that corresponded to the production of 3 specimens per % of water added in each of the established mixture designs. The compressive strength of the cylinders made in the materials resistance laboratory of the Universidad Francisco de Paula Santander, San José de Cúcuta, Colombia was tested. It was concluded in the influence of the % of water in the mechanical resistance of the experimental mixtures and the viability of the use of this type of mixtures in the elaboration of nonstructural concretes, data of importance with which the construction costs would be reduced considerably, generating in turn, a positive environmental impact by means of the inclusion of residual materials in the concrete mixtures.
Evaluation of electrochemical phenomena of fly ash and blast furnace slag in commercial cement mixtures
Authors: Hernández Carrillo C G , Gutiérrez-Junco O J , Sarmiento Rojas J A
Published: November 2019

Steel reinforced concrete is the most commonly used composite material in construction; however, large amounts of energy, natural resources are required for its manufacture and is susceptible to corrosion in the presence of aggressive environments. However, there are alternatives aimed at sustainable development, through the gradual replacement of ordinary cement with other Supplementary cementitious materials. Consequently, the present investigation evaluates the effect of fly ash and granulated blast furnace slag on the electrochemical phenomena of steel bars, embedded in a cement paste matrix, characterized by scanning electron microscopy, X-ray fluorescence and area surface to establish variations in electrochemical phenomena evaluated by Tafel extrapolation curves, half-cell potential, resistance to linear polarization and electrochemical impedance spectroscopy. The electrochemical conditions show that the surface areas and composition affect the passivation degree; therefore, mixtures with FA generate passive protection and on the contrary, the mixture with GBFS does not present any type of corrosion protection.
Evaluation of corrosive behavior of chromium silicon nitride under hydrodynamic conditions in aggressive environments
Authors: Villate J J , Vera E , Olaya J J
Published: November 2019

In order to analyze corrosion resistance and wear behavior, steel cylinders were coated with chromium silicon nitride via physical vapor deposition, using a reactive sputtering magnetron, with base and working pressures of 4*10−6 mbar and 8*10−3 mbar respectively. The diffraction patterns correspond to chromium nitride and the amorphous phase of silicon nitride, hardness of 6.52 GPa, thickness of 3 μm and chemical composition characterized by nitrogen, silicon and chromium. The corrosion behavior was determined with a rotating cylinder electrode, rotating at different speeds and connected to a Gamry potentiostat galvanostat, using the techniques of polarization resistance, electrochemical impedance spectroscopy and dynamic potentiation polarization. The tests were carried out in solutions composed of water, 1% of sodium chloride and silica sand, with temperatures of 25 °C and 45 °C. Limiting current density behavior was evidenced. The coating corrosion rate was reduced by up to two orders of magnitude compared to that found for steel samples and was affected by the system rotation speed, particle size and electrolyte temperature.
Durability considerations for mitigating corrosion caused by biogenic sulfuric acid in sewerage systems
Authors: Cortés M , Vera E
Published: November 2019

In sewerage systems, the corrosion process caused by microorganisms, has been studied. This affects the structural integrity of the concrete drainage pipes and the sewage treatment plants, This article is a review of research which focuses on the study of how to reduce the production of hydrogen sulfide, how to improve the resistance of concrete through the use of additives and the implementation of antimicrobial techniques to reduce bacterial growth, This review allowed us to find a way to improve the physical simulation of exposure to the corrosive medium through chemical tests, as well as the optimization and choice of the type of zeolite that would be incorporated into the mixture with which concrete pipes are normally manufactured. for sewers in Colombia improving their durability conditions.
Evaluation of mechanical wear in bismuth-titanium coatings synthesized by the sol-gel method and applied on 316 L stainless steel substrates
Authors: Garzón P , Bautista-Ruiz J , Chaparro A
Published: November 2019

Steels are part of the basic equipment of most of the industrial framework, including very diverse sectors such as the oil, chemical and automotive industries. However, steels are susceptible to wear phenomena limiting their life in use and losing efficiency in the applications to which it is intended leading to a technological and economic problem. In mechanical systems, lubrication requires effective strategies to ensure that the increase in critical contact voltages does not cause material failure during operation. Although there are different ways to avoid the wear of steel parts, the development of material technology has allowed the manufacture of new alloys with anti-wear properties. Replacing steels with other higher cost materials is very unfeasible. For this reason, one of the alternatives of greatest interest to reduce wear is based on the surface modification of the metal through the use of coatings. The sol-gel method allows the manufacture of coatings on steel parts to reduce wear. The objective of this work was to manufacture, using sol-gel, bismuth-titanium coatings on 316 L stainless steel substrates in order to analyze the mechanical wear of the system and evaluate its wear rates and friction coefficients. The study focused on determining the effect of precursor concentration on performance as a film to reduce wear. It was determined that the friction coefficients show significant variations due to adhesive wear processes. With respect to wear, it is concluded that the coatings offer substrate protection by indicating wear rates lower than those reported for 316 L stainless steel substrates without coating.
Yttrium oxide evaluation as coating to reduce the corrosion velocity in industrial equipment working under combustion environments. Case study: Ferritic 9Cr-1Mo steel
Authors: Alviz-Meza A , De La Cruz W , Kafarov V , Ostos Y , Peña-Ballesteros D Y
Published: November 2019

The well-known scientific problem about global warming and less cost energy requirement, has been boosting to the petrochemical sector to implement eco-efficiency strategies by promoting the use of critical conditions throughout the traditional chain process of oil refining. In addition, many industrial combustion processes are developed using as energy source a mixture of natural and recovery gases, which added to high temperatures generate potential corrosion atmospheres. Thus, this research aims to try to reduce the pipeline degradation that take place in combustion environments by evaluating an yttrium oxide as coating for the ferritic 9Cr-1Mo steel. This coating was deposited on the substrate by plasma laser deposition, and several growth times were implemented to evaluate its thickness effect. On the other hand, in order to obtain the real combustion atmosphere, a flue gas model composition was selected, which was useful to calculate the theoretical oxidation products by simulation. Finally, those coatings were evaluated at 650 °C and testing times from 1 hour to 100 hours inside the calculated oxidation environment. The main results indicated that even with the tested coatings, the evaluated alloy had a severe corrosion velocity, but lower than without them.
Rotodynamic pump operating as a motor machine
Authors: Hernández E , Mantilla J C , Cordoba E
Published: November 2019

Rotodynamic pump is a commercial machine and very used in the factories so the use of centrifugal pumps or rotodynamic pump operating as turbines or motor machine offers a technically and economically viable alternative to traditional turbines, the selection and implementation of a pump that functions as a turbine is a subject that is still under development. In this investigation the process of selection and implementation of the centrifugal pump is performed where centrifugal pump works in reverse mode, as a turbine, and mechanical adaptations are made for proper operation. The hydraulic system consists mainly of a forced pipe and a tank at a height of 13.3 m. In the built equipment a maximum efficiency of 58% was obtained at 890 rpm and an electric power of 45 W with a consistent load of a 120 V and 70 W bulb. The results obtained in this case study are comparable with the results of conventional turbines.
Estimation of potential hydrogen production from palm kernel shell in Norte de Santander, Colombia
Authors: Acevedo J C , Solano S P , Durán J M , Posso F R , Arenas E
Published: November 2019

This work sought to estimate the economic and environmental potential of palm kernel shell for hydrogen production as energy vector in Norte de Santander, Colombia. A field research determined that the department generates monthly 14082 t of palm biomass of which 12501 of palm kernel shell remain available for their use. The proximate and ultimate analyses of the palm kernel shell report high heating value (19.53 MJ/kg) compared with other agro-industrial biomasses, high content of volatile material (69.82% w/w) and fixed carbon (21.68% w/w), promoters of chemical reactions in pyrolysis and gasification processes, respectively. In the Aspen Plus® simulation process of the palm kernel shell gasification at 900 °C and steam/biomass ratio of 1.5, a yield is obtained of hydrogen production of 40.7%, equivalent to a monthly production in Norte de Santander of 51.6 t. Using H2 in the generation of electric power permits producing 470.9 MWh/month that represent theoretical utilities of US$27734.5. In another scenario, 55848.8 gal/month of gasoline are substituted, equivalent to US$11708.6 through the sale of carbon credits. Regarding diesel, 45905.1 gal are replaced per month, which add US$9725.4 through the commercial transaction in the carbon market. It is concluded that using palm kernel shell as primary source to obtain H2, has, in principle, a favorable economic and environmental impact for sustainable development of the department of Norte de Santander, besides contributing to the knowledge base on the penetration of this vector in Colombia’s energy matrix; however, more detailed technical and economic studies are needed to conclude regarding the economic viability of this energy conversion process.
Synthesis of a chalcopyrite material, based on CuIn1−xGaXSe2(X = 0.3 y 0.5), for application as semiconductor layer, deposited by a low-cost technique
Authors: Castellanos Báez Y T , Torres-Barahona E A , Gómez-Cuaspud J A , Vera-López E , Pineda-Triana Y
Published: November 2019

The current work reports the synthesis and characterization of a photovoltaic material based on the CuIn1−xGaXSe2(X = 0.3 y 0.5) system, making use of the doctor blade method. For this purpose, homogeneous inks were obtained and worked under previous stoichiometry arrangement. The deposition process of thin films, were made in a heating plate on conventional glass substrates, previously washed and treated for this purpose. Once the layers of Cu, In, and Ga were deposited by chemical bath, a thermal treatment was performed at 550 °C for 30 min in a conditioned oven, in which the selenization process was performed. The obtained films were characterized by X-ray diffraction, Raman spectroscopy, solid-state impedance spectroscopy, UV spectroscopy and scanning electron microscopy techniques. The identification of the main crystalline phase could be corroborated, as well as the conductive and optoelectronic behavior of the solids in accordance with reported in literature. Simultaneously, it was checked that the method used allows obtaining layers of an optimum thickness, in order to be used as an absorbent layer in the design of solar devices.
Evaluation of semiconductor materials by hydrothermal synthesis
Authors: Pérez Bustos H G , Gómez-Cuaspud J A , Pineda-Triana Y , Vera-López E , Patarroyo-Mesa M
Published: November 2019

The present work describes the obtaining of semiconductor materials with kesterite structure by a hydrothermal methodology. The obtained kesterite has a structural modification of the conventional Cu2ZnSnS4structure with the insertion of titanium instead of tin, in order to obtain Cu2ZnTiS4. The precursors of this material, metallic salts of copper, zinc acetate, titanium butoxide and thiourea were added in a hermetic steel reactor, controlling time (24 hours, 48 hours and 72 hours) and temperature (200 °C — 300 °C). To evaluate the synthesis, the materials obtained were analysed by different characterization techniques (X-ray diffraction, scanning electron microscopy, solid state impedance). The results show that material with the conditions of synthesis 48 hours and 300 °C, exhibit the best textural and electrical results in terms of economy process. The X-ray diffraction analysis shows secondary phases, which can possibly be eliminated with a thermal treatment, since most of the secondary phases (such ZnS and Cu2S) can be eliminated by combustion in an inert atmosphere. The results showed that the increase in the temperature of synthesis decreases the formation of amorphous agglomerates, improving the morphology of the material. The characterization of the materials showed that the Cu2ZnSnS4phase is possible to obtain by hydrothermal synthesis.
Obtaining biogas for use during construction of residential buildings
Authors: Forero K K , Torrado K A , Gómez F R , Guarín O D , Ardila D F , Tiria L C
Published: November 2019

The present study examines the technical and economic feasibility of a biodigester to generate biogas from organic waste, such as human and food residues, generated during construction projects. Based on existing data and the scaling model selected, the quantity of such waste was estimated on a per-worker basis over a period of 30 days; yielding a daily average of 86 grams of food waste, 250 grams of stool, and 1.5 liters of urine. These estimates are scalable for the calculation of periods of greater or lesser duration. The data, variables, and calculations were analyzed using a technological tool developed for this study, such that other users or parties interested in the use of a biodigester for the management of organic wastes and biogas generation in construction projects can enter the relevant data for their project and generate scaling and cost data as an output. The use of a biodigester for construction projects is based on real-life experience in various sectors, for the most part in rural areas and domestic applications; while factors such as space, maintenance, and safety, among others, have hindered the use of this technology in the construction sector. Nevertheless, its implementation in new construction projects drives positive social, environmental, and economic impacts, as it reduces the volume of organic wastes for disposal, and substitutes for the use of fossil fuels. The latter results in a reduction of pollution, and improves the environment, with corresponding positive effects upon human health and wellbeing. It also represents an opportunity to reduce the cost of gas consumed during the construction process of residential buildings.
Design of a solar power system in San Agustin building Ocaña, Colombia
Authors: Arévalo J , Cabellos M I , Marquez R T
Published: November 2019

The purpose of this study is to design an autonomous solar system as an alternative to the electrical energy use of San Agustín building in the municipality of Ocaña, Colombia. The building has 8 floors of which the commercial and administrative zones consume 2447.2 Wh per month. Considering that electricity costs are high, the project focuses on lowering energy consumption in the billing. The research is carried out with the development of the phases of analysis, diagnosis, and design, in order to encourage the use of renewable energy in the building. The academic study is limited to providing the design of the autonomous system to the owners of the building to continue with the investment phase. The results are based on establishing the structural and energy parameters and validating the implementation of the solar power system taking into account electricity prices, which results in the use of 15 panels of 275 Watt and 7 panels of 325 Watt with a saving of approximately 1.500.000 Colombian pesos.
Biomethane production potential from selected agro-industrial waste in Colombia and perspectives of its use in vehicular transport
Authors: Posso F , Mantilla N
Published: November 2019

The proper disposal and management of the waste generated from the agro-industrial activity in Colombia constitute a problem with environmental, economic and social implications, such that its solution constitutes a matter of national interest. Thus, the objective of this work is to estimate the potential of biomethane production by biochemical conversion of selected agro-industrial waste and, its use is proposed in vehicular transport currently moved by natural gas. Methodologically, the study relies on official statistics of the national entities that report the volume of crops and waste generated yearly, Three crops were selected, applying criteria of abundance, geographic distribution, and energy properties: sugarcane, palm oil, and rice; the waste considered for each of them were sugarcane bagasse, empty fruit bunches of palm oil and rice straw. The conversion of said waste to energy vectors is by anaerobic digestion producing biogas, and from its purification, biomethane. The volume of biomethane obtained was 1,290x106 m3/year. This important value was compared with studies from other countries. The prospects for the final use of biomethane as vehicle fuel are promising. So, biomethane is a potentially attractive develop option in Colombia, which would make it necessary to carry out more specific and detailed studies include economic, environmental and social aspects that would positively impact the route to the sustainable development of the country.
Analysis for the implementation of a system for natural gas liquids removal and recovery at the gas processing plant El Centro in Santander, Colombia
Authors: Agón-León C , Sanabria-Cala J A , Conde-Rodríguez G R , Laverde-Cataño D , Peña-Ballesteros D Y , Estupiñan Durán H A
Published: November 2019

The present work carried out the analysis of seven natural gas liquids removal and recovery technologies, evaluating ten decision criteria to identify the technology with the highest technical and economic potential to be implemented at the gas plant “El Centro”, Colombia. The technical criteria evaluated took into account: the chemical composition of the natural gas processed; the flow, pressure and temperature of the system; the efficiency in the removal of natural gas liquids and the technology adaptability against fluctuations that may occur in the operating conditions. On the other hand, the economic criteria evaluated included the purchase of high–cost supplies and equipment, as well as space and maintenance requirements for their implementation. Based on the analysis, the triethylene glycol improved absorption process was established as the technology with the greatest potential to be implemented at the gas plant “El Centro”, Colombia, so it was evaluated in a pilot test where a reduction of 30 °F on the cricondentherm point was observed, associated to the removal of higher molecular weight hydrocarbons from the natural gas stream.
Internal inspection of the Lisama – El Centro gas pipeline using magnetic flux leakage technology in Santander, Colombia
Authors: Vargas-Gutiérrez D , Sanabria-Cala J A , Conde-Rodríguez G R , Laverde-Cataño D , Peña-Ballesteros D Y
Published: November 2019

The present work carried out the internal inspection of the pipeline that allows the natural gas transport from the “Compresora Lisama” to the gas plant “El Centro” in Santander, Colombia, establishing the current pipeline conditions and defining the actions that must be taken to maintain the safety of the process. The internal inspection was carried out using Magnetic Flux Leakage technology, which allowed identifying in a single run the different types of anomalies that may occur in the 8” diameter steel pipeline during natural gas transport. The anomalies identified during the internal inspection inherent to natural gas transport through water bodies and unstable soils of variable height corresponded to thickness losses, dents, and programmed anomalies with estimated repair factor greater than 1. These anomalies were grouped into a total of 41 sections of the “Lisama–El Centro” gas pipeline that require replacement to guarantee the correct operation of the “Compresora Lisama” and the gas plant “El Centro”, preventing unscheduled plant shutdowns that may lead to shortages in communities and companies that require daily the natural gas.
Methodology based on cross modal strain energy method to estimate the damage severity in a metallic structure
Authors: Sánchez-Acevedo H G , Rodríguez G H , González-Estrada O A
Published: November 2019

The studies related to the Structural Health Monitoring have been important to evaluate the operation condition of structures, and let reduce the maintenance costs. The modal strain energy method has been used for this goal. This method requires to compare the information of mechanical vibrations acquired from the structure vs the same structure in initial conditions, called structure in health condition. This work is focused on developing a methodology that differs from the traditional modal strain energy. The methodology allows us to identify and evaluate the damage severity using a severity indicator.The methodology has been implemented in an offshore structure. The results have been satisfactory for the damage quantification for single and multiple damages.
Observation of significant differences between electromagnetic and acoustic emissions during fracture processes: A study on rocks under compression loading
Authors: Clavijo J , Wang H , Sánchez S
Published: November 2019

Electromagnetic radiation (known as electromagnetic emissions) related to processes of loading and fracture in different types of materials (from metals to rocks) has been widely reported. The physical mechanisms behind these emissions are still under discussion, however, it is commonly accepted that they are created by some of the micro-cracks that appear in the sample during fracture processes. Nucleation and growing of micro-cracks generate mechanical waves (acoustic emissions), therefore, each electromagnetic emission should be linked with some acoustic event. Furthermore, it is expected that the electromagnetic and acoustic activities (number of emissions per second) have the same general characteristics. Contrary to what is usually reported, we find that there are significant differences between acoustic and electromagnetic emissions in loading processes on rocks. These differences were detected during the compression of a typical laboratory-scale sample of granite when it is compressed at a rate of around 20 kPa/s. We found two important discrepancies: i) There were at least 20 electromagnetic bursts (out of around 200) that were not coincident with any acoustic event. ii) The electromagnetic activity in general shows its maximum value when acoustic activity is very low. Both emissions just coincide at the moment of the final collapse. These results strongly suggest the existence of a non-fracture mechanism related to the origin of electromagnetic emissions. This could have important consequences for the field of non-destructive assessment of materials and even in the study of earthquake precursors and forecasting.
Bifurcation analysis of the threshold of a solid-state laser
Authors: Mesa F , Correa G , Cárdenas P
Published: November 2019

In this paper we describe the qualitative analysis of the dynamic model of a solid-state laser. Initially a brief description of the theory of dynamic systems is made, the part concerning the qualitative solutions of non-linear models, the obtaining of fixed points for second-order systems and the determination of the stability of these points. Later, the dynamic model of the solid-state laser is exposed, where all its inherent parameters and the behavior that follows will be described. Then, the qualitative analysis is developed where the model will be converted to dimensionless equivalent that contains two parameters that condense to all the others. The results obtained are verified with numerical analysis, there clarifies the veracity of the qualitative analysis in conjunction with the description of the behavior of the solid-state laser, to finish with the conclusions obtained from the whole development.
Bifurcation analysis field potential in isotropic materials defined by semi-spherical layers using finite elements
Authors: Ospina R , Correa G , Cardenas P
Published: November 2019

In this document, the finite element method is developed in three dimensions to find the potential field in a region composed of hemispherical shells defining subregions with different materials, the numerical solution is made by FlexPDE software version 7.12 and the general process to solve is shown Problems of three-dimensional differential equations using the Galerkin criterion to approximate functions by the linear combination of functions of form, thus, the differential problem is reduced to solve a set of algebraic equations to find the coefficients of the linear combination.
Thermal and fluid-dynamic analysis of an automotive disc brake with ventilation pillars aerodynamic type
Authors: Rivera-López J E , García-León R A , Quintero-Orozco A , Diaz-Torrez E J , Gutiérrez-Paredes G J , Echavez-Diaz R , Arévalo-Ruedas J H
Published: November 2019

The braking system of a car must work safely and predictably in any circumstance, which implies having a stable level of friction, in any condition of temperature, humidity and salinity of the environment. For a correct design and operation of the brake discs, it is necessary to consider different aspects, such as the geometry, the type of material, the mechanical resistance, the maximum temperature, the thermal deformation, the cracking resistance, among others. The objective of this study was to analyze the behavior of temperature, velocity and heat flow, in the ventilation duct of an automotive disc brake with ventilation pillars different from conventional using computational fluid dynamics. The SolidWorks Simulations design software was used to analyze the behavior of the fluid (air) in terms of speed and heat dissipation capacity. The numerical results for the heat flow through the ventilation channels were compared with the results obtained mathematically. The numerical results showed that the discs performed well under severe operating conditions. In the design of the brake disc is very important to select the appropriate geometry, particularly the number and the cross section of the ducts in addition to that, the type of material. Numerical methods offer advantages through the software tools for selecting geometry and material and for modeling fluid flow to optimize heat dissipation to provide maximum performance for properly maintained components.
Optimization of the connecting rod of a two-stroke engine using finite element analysis
Authors: Valero-Páez L B , Chacón-Velasco J L , González-Estrada O A
Published: November 2019

In this work, the mechanical behavior of a connecting rod of a two-stroke single-cylinder engine is studied by means of finite element analysis to reduce its weight. We investigated the static and dynamic stresses on the parts of the connecting rod, considering the boundary conditions of the Jovaj theory for the design of automotive conrods. Then, the maximum stresses of the models were compared to perform the optimization of the weight of the connecting rod, evaluating the sensitivity of the prototype, and geometry restrictions. For the study using finite element analysis, a connecting rod prototype designed at Universidad Industrial de Santander was used, within the project of reengineering the connecting rod of a two-stroke engine of small displacement for agricultural applications. The mechanical response of the designed conrod was evaluated, taking into account the mechanical stresses to which it is subjected during the operation of the engine. Finally, the design was revised to propose preliminary improvements in the geometry using topology optimization.