Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

One of the basic processes in any entity to guarantee its economic sustainability is the maintenanceprocess. The objective of this work was to analyze the different tools applied for the diagnosis ofmaintenance management through a bibliographic review carried out in this field and jointly thedemonstration of the need or not to have a model that measures the maturity in the maintenanceprocess in organizations. For the analysis, the analysis and synthesis method was used, as well as theconglomerate analysis method. A total of 33 tools were analyzed, showing the characteristics of eachtool in the form of tables, applying descriptive statistical analysis. The bibliographic study providesresearchers with the benefits and insufficiencies for the selection of tools that are best contextualizedto their field of work, within maintenance, thus enhancing decision-making in the face of theproblems presented. In addition, a maintenance concept is proposed in close relation to its functionand objective.

Much of the oil deposits contain heavy hydrocarbons, the extraction of which is difficult due totheir high viscosity. Magnetic technology has been one of the methods used to solve theseproblems. The objective of this research was to evaluate the rheological behavior and viscosityof several magnetically treated samples of Cuban oil. For this, oil samples with differentphysical-chemical characteristics were used to delve into the relationship between the nature ofthe fluid and the magnitude of the observed effect. A 0.47 T magnetic conditioner was designedand the experimental installation was validated as a prediction and diagnostic method for itsapplication in oil handling. The magnitude of the effect observed in magnetically treated crudedepends largely on the chemical-physical characteristics of the fluid, such as the content of waterand asphaltenes, viscosity, density, among others. In this research, the greatest effects areassociated with crude oils with high viscosity and high asphaltene content. The magnetictreatment used decreased the viscosity of several samples of Cuban crude oil from 7.6% to98.17% at different velocity gradients. The rheological behavior of the crude oil samples studieddoes not change with the magnetic treatment used, but there are changes in the coefficients of therheological models; decreasing the consistency index in all the analyzed samples, whichcorresponds to the decrease in the viscosity of the samples after the magnetic treatment.

The need for sustainable development and greater energy efficiency in the paving area has driven the search for mixing and compaction temperatures for asphalt mixtures lower than those conventionally used. In search of lowering the paving temperature and lowering energy consumption, it is sought to replace hot asphalt mixes with warm mixes. The use of oleic additives as asphalt binder modifiers can be a viable and environment-friendly modifier due to the possibility of promoting reductions in binder viscosity and a decrease in mixing and compaction temperature. Thus, this study evaluated the physical and rheological characteristics of the asphalt binder classified with 50/70 penetration modified by the addition of refined cottonseed oil at levels of 1%, 2%, 3%, 4%, 5%, and 6%. The samples were analyzed before and after the short-term aging procedure (Rolling Thin-Film Oven-RTFO), by means of Penetration, Softening Point, Rotational Viscosity, Performance Grade (PG), and Multiple Stress Creep Recovery (MSCR). The results showed that the addition of oil at the levels studied made it possible to reduce the mixing and compaction temperatures of the asphalt mixtures by up to 10ºC for the highest oil content added to the asphalt binder. Refined cottonseed oil presented itself as a good viscosity and working temperature reducer modifier for asphalt mixtures, where all tested contents were classified for use on standard traffic roads.

This work presents an evaluation of the voltage values at the point of common coupling of asecondary electricity distribution network after the insertion of a photovoltaic distributedgeneration unit, located in a city in the northeast of Brazil. With this evaluation, it was possible toverify whether after the insertion of photovoltaic distributed generation there was a violation of thevoltage limits determined by the National Electric Energy Agency. To evaluate the voltage values,computer simulations of a real distribution network were carried out, considering its constructivecharacteristics, as well as the power demand of the consumer units connected to the network, theinstalled power of the generation unit and the local solar power and temperature. The simulationswere carried out considering the months of the year to analyze the influence of seasonality on thechange in the simulated voltage values. With the results obtained, it was found that the insertion ofphotovoltaic distributed generation can cause more than 20 violations of the voltage limit over themonths, causing financial damage to the energy concessionaire. Voltage limit violations occurred45.83% of the time at 1 pm, indicating that the occurrences are recurrent at times of high generationand low consumer demand, increasing the voltage value at the common coupling point of thedistribution network. Thus, it was possible to identify the instants in which the operation of theprotection system of the distribution network is compromised, so that later it is possible to proposemethods to regulate the voltage at the point of common coupling.

Well cementing is a routine activity in the oil industry, but requires a series of care, as it is an expensive activity that, when not carried out properly, can cause extra expenses in addition to environmental damage. This work aimed to determine statistically defined compositions of a material that can efficiently replace Special Portland Cement for oil wells. For this, the characterization of the materials was carried out by means of laser granulometric analysis, chemical analysis, X-ray diffraction, and thermal analysis. The compositions were determined using the mixture design methodology, using the central composite experimental design (CCD), and subjected to simple compressive strength tests and thermal analysis, to determine optimal compositions with the closest approximation to the characteristics of Special Portland Cement. for oil wells. The results obtained pointed to the feasibility of using the mixtures found, allowing the definition of 9 compositions that presented satisfactory performance, and can be used for this purpose. Therefore, it was concluded that the compositions found and the models developed presented a potentially satisfactory performance for use as an alternative material for oil wells, requiring mechanical and economic validation for its use.

Technological change has been a subject of great interest in economic analysis because it isresponsible for most of the increase in productivity, and therefore is a fundamental factor in theproduction growth. Similarly, technological progress is of great help in explaining the changes ineconomics and other trends related to modern economic growth. Under this, a problem that is crucialfor the economic development of Mexico is its low economic growth and the consequent inability togenerate the necessary jobs, due to a difficult framework to increase productivity. Therefore, theobjective of this work is to design and simulate a dynamic stochastic model for the Mexicaneconomy, incorporating specific and neutral technological disturbances, through optimizationmethods such as evolutionary algorithms. Among the main results is that the disturbances introducedto the model have different effects separately, since their impact is not the same for all the variablesof the model. Likewise, it was found that the specific investment disturbance has a greater effect onthe production function than that of the evolutionary disturbance carried out with the geneticalgorithm, but that simulated at the same time, a sustained and more balanced growth can beobtained, which differs quite of the traditional models. As conclusions, it was possible to develop adynamic and chaotic model capable of evolving over time and that optimizes the labor and capitalfactors, thus providing a better tool to understand and develop more complex models of economiccycles.

Since March 2020, La Plata city (Buenos Aires, Argentina) has registered movement restrictions dueto the COVID-19 pandemic. Because of it, in September 2020, to carry out a prediction study ofwhat are the logical deadlines in which the paving works could be postponed during the year 2021,based on data provided by Google. The study is based on the impact that a decrease in traffic wouldhave on the useful lives of different urban road works (conservation, rehabilitation, and new workcarried out prior to restrictions), both those registered and those predictable by means of a trendmodel. The result obtained is useful for municipal authorities, who can thus allocate resources toother activities of higher priority during that period, without there being a deterioration in the state oftheir road network above that which was already admitted prior to the pandemic.With the advance of time, the most complete series of Google data is available until mid-2021, whichallows to corroborate or adjust the predictions made, seeking to obtain a logical updated value todefer the works in the first half of 2022. As a relevant result, the interventions can be deferred forseven months and a half due to the restrictions imposed, optimizing in this way the availableresources.

One of the most used forming processes for series production is the cutting of metal sheets. Thetensional behavior of the cutting tools is an extremely important issue in the aforementionedprocess. In this research, using the Finite Element Method, the cutting of 16 mm diameter holes in2 mm thick plates is simulated. Geometric parameters of the cutting punch are analyzed, such as:the variation of geometry of agreement radius and eccentricity between Punch Symmetry Line(PSL) and Shear Force of Gravity Center (SFGC), to determine their influence in the stress state ofsaid tool. It is evident that the use of the Bezier radius in metal cutting punches guarantees aresistive reserve over punches with circumferential radius. There is an increase in the stress valueas the eccentricity between the PSL and the SFGC increases; finally, the influence of this geometriccondition on the stress behavior of metal cutting punch is related in a mathematical model, alsotaking into account the geometric typology of agreement radius.

The use of industrial wastes as feedstock for biofuels production is an effective option for reductionof fossil fuels dependence and the environmental impact these wastes generate. The behavior ofblends of fatty acid distillates and diesel fuel are in this work assessed. The fatty acid distillates are aby-product of the vegetable oil refining industry and its blend are on a Lister Petters diesel enginetested. First, physical tests are developed focused on density and viscosity determination. The testsare developed on an engine test bench prepared for performance and combustion assessment. Fromthe obtained results, and important increase on exhaust emissions and 7% increase of specific fuelconsumption and HC and CO in 76% and 58% respectively. As part of the conclusions, the chemicalconversion is the only effective route to use this by-product for fueling diesel engines. If thisconversion is avoided, the fatty acid distillates cannot directly used on engines and only blends are apartial solution because the pre-heating of the distillates are not enough to decrease the viscosity ofthe fuel to the levels required by the standards. The best solution for the use of this by-product as abiofuel for diesel engines is through the chemical conversion to methyl esters.

Introduction: In recent years the use of the radial approach as a form of access for diagnostic and interventional studies has become increasingly important and of interest in interventional cardiology services worldwide. Our country has not escaped this boom due to the low complication rate and greater patient comfort. Objective: To characterise percutaneous coronary intervention using the radial access route in patients attended at the Institute of Cardiology and Cardiovascular Surgery. Methods: Observational, descriptive, cross-sectional study. The sample consisted of 211 patients who underwent percutaneous coronary intervention via the radial access route. Results: Male sex predominated (61.2%). Mean age was 60.1 ±9.8 years. Chronic coronary syndrome (76.3%) was the most common diagnosis, hypertension the most frequent risk factor (73.9%) and ischaemic heart disease (30.3%). Elective intervention was performed in 76.3% of cases, using the right radial approach in 88.2%. Two- and three-vessel disease was demonstrated in 45.1% of patients. The procedure was successful in 96.7% of patients. Variables demonstrating statistically significant relationship with failure were: left ventricular ejection fraction < 40% (p(0.0001), glomerular filtration rate ≤ 60 ml/min (p=0.002), history of ischaemic heart disease (p= 0.016) and presence of 3-vessel coronary artery disease (p= 0.019). Conclusions: Percutaneous coronary intervention via radial access in ICCCV is safe and effective, with a high success rate and few complications.