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

Context: modeling of atmospheric pollutants is an useful tool for air quality monitoring and management. In this study the dispersion of three atmospheric pollutants (SO2, NO2 and Total Suspended Particles - TSP) emitted by a boiler from a paper factory at Valle del Cauca department was estimated and its potential impact on the population settlements located at 5Km around the stationary source was identified.Method: the study was structured in three stages: (i) compiling and processing of meteorological, topographic and isokinetic sampling data; (ii) modeling the dispersion of pollutants using AERMOD ViewTM; and (iii) determination of the impact on surrounding populations.Results: the pollution plume is dispersed towards predominant directions of wind and the trajectory is affected by mountainous topography. The maximum concentrations of pollutants found (0,012 μg SO2/m3, 1,42 μg NO2/m3 and 0,109 μgTSP/m3) were lower than the Colombian air quality standards.Conclusions: the emission-control systems used by the studied paper industry ensures compliance with the air quality standard and generates a low impact on exposed populations. In addition, the atmospheric instability conditions favored the dilution of the contaminants discharged to the atmosphere. Although the AERMOD model was useful in the modeling of pollutants under atmospheric instability conditions and short length (<5 km), it has limitations to simulate the chemical transformations of SO2 and NO2, therefore it is recommended to evaluate other models that allow a comparative analysis and select the most appropriate model.

Context: The energy and environmental panorama that our societies confront nowadays, demand for renew-able, clean and abundant sources of energy, not reliant on fossil fuels and detached from the geopolitical pressures the latter represent. In this scenario solar thermal energy arises as a viable and functional option. The main disadvantage of this emerging source of energy lies in the intermittent availability of solar radiation. Because of this difficulty, efficient processes for the storage of thermal solar energy becomes a highly relevant area of research. The aim of this paper is to present a survey on this topic.Method: A bibliographic review was carried out using the Scopus catalog. The search criteria for this purpose was defined using the following terms: solar+thermal+energy+storage+materials. This search pattern was applied to the title, abstracts and keywords of the contributions. Using the bibliometric tools of the citation database, the most cited documents were selected and the survey was developed.Results: A growing interest in the scientific community regarding this energy practice is evident starting from 2010. Characteristics, advances and trends in systems that use thermal energy storage materials are presented for sensible and latent heat, materials compound changeover phase, and finally thermo-chemical thermal storage materials.Conclusions: Improving the thermal conductivity of thermal storage materials is an important trend in current re-search. On the other hand, profitable practices for micro-encapsulated phase change materials and composite materials are analyzed. The optimization of thermo-physical properties as the melting point of thermal storage materials is explored with techniques such as eutectic mixtures and hydro-carbon chain length. Although the thermochemical materials are still in laboratory stage, they have a great potential as thermal storage materials in the future, given their large energy storage capacity per unit volume.

Context: The currency market is known as the most liquid market in the financial system. Its strong repercussion in the economy is tied to the capitalization and the impulse that this market offers through the increase of investments and therefore of macroeconomic effects that is found in the development of the economy, For these reasons, it is relevant to study models that predict the behavior of the main Latin currencies.Method: Two models are proposed for the prognosis and the identification of factors implicit in the behavior of these currencies. The first proposed model corresponds to the Black-Scholes, which allows obtaining the future price of the currency based on integrating price processes, a Wiener process and a static volatility is recognized. The second model is Heston, which describes the evolution of the volatility of an underlying asset and assumes a stochastic volatility.Results: After the application of the proposed mmodels, their efficiency are evaluated by means of the Diebold-Mariano Test, in order to identify the forecast model that best adapts models, their efficiency are to the real behavior of the parities.Conclusions: It is identified that the Heston model offers a better fit to the forecast, assuming random volatility in the short term for each of the currencies, while the long term presents the largest adjustment of the Black & Scholes model, It is evident that the longer the forecast time, the greater the uncertainty and the greater the prediction error.

Context: The concept of self-organization plays a major role in contemporary complexity science. Yet, the current framework for the study of self-organization is only able to capture some of the nuances of complex social self-organizing phenomena.Method: This article addresses some of the problematic elements in the study of social selforganization. For this purpose, it focuses on pattern formation, a feature of self-organizing phenomena that is common across definitions. The analysis is carried out through three main questions: where can we find these patterns, what are these patterns and how can we study these patterns.Results: The discussion shows that there is a high level of specificity in social self-organized phenomena that is not adequately addressed by the current complexity framework. It argues that some elements are neglected by this framework because they are relatively exclusive to social science; others, because of the relative novelty of social complexity.Conclusions: It is suggested that interdisciplinary collaboration between social scientists and complexity scientists and engineers is needed, in order to overcome traditional disciplinary limitations in the study of social self-organized phenomena.

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Context: Organizations today must select suppliers effectively to provide a timely response to the needs of their customers and thus ensure their competitiveness. The objective of this study was to establish a systematic procedure for the selection of suppliers linking the hierarchical analysis process (AHP) and a mixed integer/linear programming (MILP). Method: A literature review was carried out in the Science Direct, Engineering Information, ProQuest and Scopus databases, which allowed identifying the most used techniques by academics, businessperson and researchers, for the selection of suppliers. The mathematical models for the AHP and the MILP were selected. The AHP was performed by means of simulation with the Montecarlo method and the MILP was validated through sensitivity analysis. In the MILP the parameters provided by Ruiz, Mendoza and Ablanedo were used, from which it was modified for different lots quantities. Results: The parameters that feed the MILP model were changed by the simulations when performing the AHP, the changes made to the parameters showed that the mathematical model is valid. It was possible to propose a procedure for the selection of suppliers that improves the effectiveness in decision making. Conclusions: The selection of suppliers is an essential aspect to guarantee the quality of the products and services provided by the organizations, therefore, the proposed procedure provides criteria for the decision of the suppliers considering units, capacities, costs and lot number.

Context:  Adsorption is a tertiary wastewater treatment that can be effectively employed to remove metal ions from aqueous solutions. Natural and modified clays and zeolites have been widely use as low-cost materials to increase the competitive advantage of the process. Methodology: A comprehensive review was made amongst articles, that during the last decade, have studied cadmium, copper and lead adsorption onto natural and modified bentonite, clay and zeolite. Results: Different process parameters, equilibrium conditions and kinetics were analyzed. Operation parameters studied were initial metal ion concentration, solution pH, adsorbent dosage and temperature. Compilation of system efficiencies, in regards to maximum adsorption capacity, is presented. Isotherm models to assess adsorption equilibrium as well as kinetic and diffusion models in studies reviewed are discussed. Conclusions: Bentonite, kaolin and zeolite have been proven to be adequate materials to remove cadmium, copper and lead from aqueous solutions. The different adsorption capacities of cadmium, lead and copper are a reflection of the influence of many process parameters. The Langmuir isotherm usually describes best the equilibrium adsorption in the articles reviewed. Finally, the pseudo-second orden model better describes the kinetics in many cases.

Context: From the Business Management model to potentiate the growth of small and         medium-sized enterprises carried out by the author of this article; it was possible to apply the same in function of the specific needs of the company object of study, determining for that the specific variables for his turn of business and conserving other variables of general. Method: The methodology used was the interview technique with the top management of the company, gathering the relevant, reliable and correct information; it was considered that when studying a certain system, it is convenient to analyze its behavior based on representative data of what is expected to be its normal functioning and not with data corresponding to extreme      situations. These interviews made it possible to determine the variables necessary for the model made. Results: Designed the model, it was possible to simulate results depending on the specific requirements of the company, visualizing the impact that these results would have the company under study. Conclusions:The conjunction of the methodology of systems dynamics, the interviews, the collection of historical data, as well as the involvement of the laws that govern these businesses in Ecuador, made it possible to obtain an applicable and reliable product for the organization.    

Context: In the industry the resources are increasingly scarce. For this reason, we must make a gooduse of it. Being the optimization tools, a good alternative that it is necessary to bear in mind. A realworldproblem is the facilities location being the Set Covering Problem, one of the most used models.Our interest, it is to find solution alternatives to this problem of the real-world using metaheuristics. Method: One of the main problems which we turn out to be faced on having used metaheuristic is thedifficulty of realizing a correct parametrization with the purpose to find good solutions. This is not aneasy task, for which our proposal is to use a metaheuristic that allows to provide good parameters toanother metaheuristics that will be responsible for resolving the Set Covering Problem. Results: To prove our proposal, we use the set of 65 instances of OR-Library which also was comparedwith other recent algorithms, used to solve the Set Covering Problem. Conclusions: Our proposal has proved to be very effective able to produce solutions of good qualityavoiding also have to invest large amounts of time in the parametrization of the metaheuristic responsiblefor resolving the problem.

Context: Order-preserving matching regards the relative order of strings. However, its application areas require more flexibility in the matching paradigm. We advance in this direction in this paper that extends our previous work [27].Method: We define γ -order preserving matching as an approximate variant of order-preserving matching. We devise two solutions for it based on segment and Fenwick trees: segtreeBA and bitBA.Results: We experimentally show the efficiency of our algorithms compared to the ones presented in [26] (naiveA and updateBA). Also, we present applications of our approach in music retrieval and stock market analysis.Conclusions: Even though the worst-case time complexity of the proposed algorithms (namely, O(nm log m)) is higher than the Ѳ(nm)-time complexity of updateBA, their Ω (n log n) lower bound makes them more efficient in practice. On the other hand, we show that our approach is useful to identify similarity in music melodies and stock price trends through real application examples.