Search

A study was prepared, which consists of the economic evaluation of two important materials in the construction of the interior partitions of the 3rd floor in a 21-floor building located in the city of Concepción. These materials are plasterboard and metalcon profiles. Within this study, the acquisition cost of these two materials was evaluated, as well as the cost associated with labor and machinery involved in the transportation process on site. In addition, the waste generated by both materials was accounted for, to quantify the costs related to waste management. Finally, a proposal is presented to achieve the optimization of these materials within the work, with the aim of achieving a better use of both. This entails great benefits for the company, since it is possible to reduce the number of materials that are currently used, and the amount of waste generated within the work. [ABSTRACT FROM AUTHOR]

Copyright of Revista U.D.C.A Actualidad & Divulgación Científica is the property of Universidad de Ciencias Aplicadas y Ambientales U.D.C.A and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The research goal was to analyze how the use of research papers can be a pedagogical strategy of active learning based on inquiry that helps mathematics students in the construction of proofs. The study was carried out under a qualitative methodological paradigm with an interpretive approach. The data were collected during a mathematical modeling course in a mathematician training program at a public university in southeastern Mexico. Nine students participated in this study and the course teacher. The data were analyzed based on the codification of the students' reasoning and strategies in their proof construction process in relation to the five components that structure a mathematical proficiency and the cycle of the four experiential learning modes. The use of research papers played an essential role in adaptive reasoning, the generation of arguments and the integration of students' knowledge when constructing their mathematical proofs on the positivity of a system of differential equations solutions and even helped to overcome such difficulties like understanding some theorems involved in proofs. [ABSTRACT FROM AUTHOR]

Copyright of Revista Avances: Investigación en Ingeniería is the property of Universidad Libre, Facultad de Ingenieria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the modelling and simulation of a complex system applying the hierarchical coloured Petri nets method to represent the failure and repair processes, as well as obtaining statistical data indicating its performance. The simulation was performed on the model of a mechanical system characterized by the FAMAE SG 542-1 war rifle, commonly used in the Chilean Army, through the CPN Tools and Python software representing how components perform of operation of this weapon. This behaviour is recorded through both software, obtaining the simulation data so that it will be possible to predict the condition of a component and the system in the future to generate corresponding action plans. [ABSTRACT FROM AUTHOR]

Copyright of Ecosistemas y Recursos Agropecuarios is the property of Universidad Juarez Autonoma de Tabasco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the performance of an artificial neural network (ANN) model in predicting the energy absorption capacity (g) of ultra-high-performance fiber reinforced concrete (UHPFRC) under direct tensile test. To avoid overfitting a data division into test and training datasets was carried out. Thereafter the neural networks were trained on the training dataset by using k-fold validation and the result model was evaluated on the test dataset. The model was capable of consider one-fiber or hybrid-two-fibers-blend as reinforced UHPFRC, of a wide range of fibers such as straight steel fibers, hooked end steel fibers, twisted steel fibers, PVA fibers, polyethylene fibers and polypropylene fibers. Experimental works were performed to validate the accuracy of the model on real data. The results demonstrated the efficiency of the model, according to the statistical parameters used for their evaluation, the accuracy and the versatility of the model when new data in considered. [ABSTRACT FROM AUTHOR]

Due the worldwide growing food demand, efforts toward to resource optimization in crops, are required. With this purpose, the use of technology is a big chance to deal these challenges, with the aim of automatizing agricultural processes. Within the tasks in agriculture, by example wedding, supply fertilizers or fungicides, the mobile robots have a potential use to assist these tasks. Then, from this work, velocity control of a differential mobile platform is developed, in order to perform precision agriculture tasks. Specifically, mathematical modelling, design of state feedback control and the integration to the robot hardware, through Hardware in the loop (HIL) simulations, validation test are performed by using ROS environment, embedded devices and mathematical simulations, at previous stage to real test. Showing a full integration of the proposed system to test and prove mobile robots. [ABSTRACT FROM AUTHOR]

Copyright of Estudios Gerenciales is the property of Universidad ICESI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Latin-American Journal of Physics Education is the property of Latin-American Physics Education Network and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bitácora Urbano/Territorial is the property of Bitacora Urbano/Territorial and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aim: The aim of this work was to estimate the efficiency of milk production in 1 168 cases in Ecuadoran Sierra Sur Andina, with the implementation of neural networks with multilayer perceptrons. Materials and Methods: These cases were collected from secondary samples provided by the Official Institute of National Statistics of Ecuador, in 2016. The variables chosen for the model were total milk production on the previous day (P), as dependent variable; and total cattle heads (CH), total laborers in the field (E), and total surface attended by laborer (S), as independent variables. The selection criteria were the existence of data from individual cases, and their impact on the dependent variable. Results: The average efficiency was 8.11 %, from which the total cases detected efficiently (> 0.70) accounted for 11 (0.9 % of the sample). Later, the cases studied were classified into three groups, depending on the efficiency calculated: Group 1 (≤ 0.4 efficiency); Group 2 (> 0.4 - ≤ 0.7 efficiency); and Group 3 (> 0.7 efficiency). Conclusion: A comparison produced several statistical differences (P < 0.01) for variables total milk production/ year on the farm, total field laborers, farm size, total cows, total cattle heads, calvings, pregnant cows, and served cows. [ABSTRACT FROM AUTHOR]

Macroeconomic modelling has been under intense scrutiny since the Great Financial Crisis, when serious shortcomings were exposed in the methodology used to understand the economy as a whole. Criticism has been levelled at the assumptions employed in the dominant models, particularly that economic agents are homogeneous and optimising and that the economy is equilibrating. This paper seeks to explore an interdisciplinary approach to macroeconomic modelling, with techniques drawn from other (natural and social) sciences. Specifically, it discusses agent-based modelling, which is used across a wide range of disciplines, as an example of such a technique. Agent-based models are complementary to existing approaches and are suited to answering macroeconomic questions where complexity, heterogeneity, networks, and heuristics play an important role. [ABSTRACT FROM AUTHOR]

Drying shrinkage is an inner phenomenon in concrete, which can generate tensile stresses in constructive elements constituted by this material and hence cracking. This paper deals with the characterization of this phenomenon in constructive works of the northern keys of Cuba. Research protocol conceived includes: characterization of existing cracks in buildings, study of materials, the experimental determination of the values of shrinkage deformations, comparison of the experimental values of deformation obtained with those provided by models of shrinkage prediction versus time, and their use in structural models of the buildings under study, to predict the structural effects of such deformations. Obtained results allow the conclusion that cracks in the studied buildings, can severely compromise the durability of the works. Comparison of the results with those provided by the theoretical models studied, lead to ensure that none of them is able to adequately reproduce the behaviour of the deformations obtained during the experimental process, showing the importance of the experimental determination of shrinkage deformation values. Although, the modelling of the effect of the shrinkage in structures shows tensile stresses surpassing those that concrete can resist, crack patterns determined by modelling coincide with the real ones that are reported in the studied buildings. [ABSTRACT FROM AUTHOR]

In this article a reflection is presented on the field of Mathematical Education which starting from the results analysis of an investigation made by the authors at the Universidad Militar Nueva Granada (2013-2014), whose purpose was the exploration of new ways for the treatment of the Calculus Problems Solving with engineering students. The new approaches pretend to go further the traditional Heuristic and Metacognitive treatments emerged specially from the Polya and Schoenfeld theories, which characterized the previously mentioned investigation and that, even though it has universally had great validity, they already deserve a review according to the present times, with the emergence of new problems and in the face of counting with technological resources that change the Mathematical Education panorama in the training of engineers. [ABSTRACT FROM AUTHOR]

An accurate calculation of lightning overvoltages is an important issue for the analysis and design of overhead transmission lines. The different parts of a transmission line that are involved in lightning calculations must be represented taking into account the frequency ranges of transients associated to lightning. In addition, the procedures to be used in these calculations must be developed considering the random nature of lightning phenomena. Several simulation tools have been used to estimate the lightning performance of transmission lines. The most popular approaches are those based on a time-domain simulation technique for which adequate procedures and transmission line models have to be developed. This paper presents a summary of the computational efforts made by the authors for the development and implementation in an EMTP-like tool of a Monte Carlo procedure, as well as the models of some transmission line components, aimed at analyzing the lightning performance of transmission lines. An actual test line is used to illustrate the scope of this procedure and the type of studies that can be performed.El cálculo riguroso de sobretensiones de origen atmosférico es un aspecto importante en el análisis y diseño de líneas aéreas de transmisión. Las diferentes partes de una línea que están involucradas en las sobretensiones causadas por el rayo deben ser representadas teniendo en cuenta el rango de frecuencia de los transientes causados por el impacto de una descarga atmosférica. Por otro lado, los procedimientos a emplear en el cálculo de sobretensiones deben ser desarrollados teniendo en cuenta la naturaleza aleatoria del rayo. Varias herramientas de cálculo han sido empleadas hasta la fecha para estimar el comportamiento de líneas aéreas de transmisión frente al rayo. Los procedimientos más utilizados emplean una técnica basada en el dominio del tiempo para la que se han de desarrollar y aplicar modelos adecuados de las distintas partes de una línea. Este artículo presenta un resumen del trabajo realizado por los autores para desarrollar e implantar en una herramienta de simulación tipo EMTP (ElectroMagnetic Transients Program) un procedimiento basado en el método de Monte Carlo que permita analizar el comportamiento frente al rayo de líneas aéreas de transmisión. Los resultados presentados en este documento se basan en una línea real cuyo análisis permitirá ilustrar el alcance del procedimiento y el tipo de estudios que se puede realizar con el procedimiento desarrollado.

La modélisation des systèmes de production est difficile en raison du nombre et de la diversité des paramètres à prendre en compte et de la complexité des relations entre ces paramètres. Dans cet article, nous nous intéressons à l´étude d´une unité complètement automatisée de fabrication de wafers semi-conduc-teurs (fab). Dans la littérature, leur analyse est très souvent réalisée en utilisant des modèles de simulation à événements discrets, mais ces travaux ne présentent pas une véritable conceptualisation du modèle utilisé. L´objectif de cet article est de conceptualiser, à travers des méthodologies formelles, tous les composants d´une unité de production microélectronique: au niveau macro, le système physique de production et son système de supervision, ainsi que, au niveau micro, le processus de fabrication. Ces approches nous aideront à identifier les objets du modèle et leurs interactions permettant ensuite de développer un programme de simulation pour l´analyser du fonctionnement dynamique du system.La modelación de los sistemas de producción es una tarea difícil debido al número y diversidad de variables que deben tenerse en cuenta y a la complejidad de las relaciones entre dichas variables. En este artículo, nos interesamos en el estudio de una unidad completamente automatizada para la fabricación de "wafers" semiconductores (llamada "fab"). En la literatura, el análisis se realiza comúnmente empleando modelos de simulación de eventos discretos, pero esos trabajos no presentan una verdadera conceptualización del modelo empleado. El objetivo de este artículo es conceptualizar, por medio de metodologías formales de modelación, todos los componentes de una planta de fabricación microelectrónica: en el nivel macro, el sistema físico de producción y su sistema de control, así como, en el nivel micro, el proceso de fabricación. Estos enfoques nos ayudarán a identificar los objetos del modelo y sus interacciones para permitir así el desarrollo de un programa de simulación para analizar el funcionamiento dinámico del sistema.The modelling of industrial systems is a very hard task because of both the number and diversity of parameters to take into account, and the complex relations between these parameters. In this paper, we are interested on the study of a fully automated Integrated Circuit (IC) semiconductor manufacturing plant (fab). In the semiconductor literature, fab behaviour analysis has very often been performed using discrete-event simulation models, but little work has been devoted to the conceptualisation of the modelling approach. Other works focus on the analysis of single parts of the fab, by simplifying the relations between its components. In such a context, the aim of this paper is to use formal methodologies to model all the components of a wafer fab, that is, its physical and control systems, as well as the fabrication process. This model specification can then be used to build a simulation model for the dynamic factory behaviour analysis.

Desde los resultados obtenidos en investigaciones didácticas en torno al proceso de la construcción de modelos científicos en el aula, en el presente artículo se examinan algunas consecuencias de este proceso en lo referente a las interacciones que suscitaría la didáctica de la modelación, dado el cambio que introduce la modelación como una intencionalidad emergente en la educación científica. En cuanto a la construcción de modelos en el aula, se precisa que el correspondiente trabajo didáctico se centra en los consensuados por la respectiva comunidad de especialistas.Based on the results obtained in didactic research on the process of scientific model constructions in the classroom, this paper examines the consequences of this process regarding the interactions that the didactics of modelling would generate, given the change introduced by modelling as an emerging intentionality in scientific education. Regarding the construction of models in the classroom, it is specified that the corresponding didactic work is focused on the ones agreed upon by the respective community of specialists.

Páramo ecosystems are located on the upper parts of the tropical mountains, below the snow line areas or in isolated areas where no glacier ecosystems occur. These ecosystems are considered important for their biodiversity, but mainly because they are permanent source of water for populations located at the upper and middle parts of the Andes. Recent studies indicate that ecosystems located at high altitudes, are more vulnerable to climate change and to changes in land use, which threatens the ecosystem services derived from them. There are very few studies in these ecosystems, within which, studies on the hydrological functioning are even scarcer, which seems to be related to their position in the top of the mountains and difficulties associated with the access to them. This implies that there is a need to create tools that allow us to study these ecosystems, overcoming the current difficulties. Hydrological TOPMODEL is used to investigate the hydrological functioning of the páramo of Chingaza, through a case study in La Chucua basin. For this, we calibrate and validate the model using two data sets of climate and the hydrology of the basin (climate and discharge from 2008 and 2009, respectively). Through the calibration procedure we obtain a high efficiency value of 0.76 model (coefficient Nash - Sutcliffe), which adequately represents the hydrological behavior of the páramo. Simulations with better adjustment between measured and predicted values of discharge, have low values of surface infiltration excess runoff, indicating high water storage capacity on the soils. This agrees with the predominance of subsurface flow in studied ecosystem, given the special characteristics of soils. Results also show the large influence of factors represented in the model (topography and soils), on water basin response to rainfall events. This is significant evidence of exceptional hydrological behavior of the páramos, mainly related to the presence of soil with high organic matter content. These results imply that TOPMODEL is a robust tool, able to represent in a precise manner the hydrological functioning of the basin La Chucua, and consequently it is expected that TOPMODEL can also represent hydrological conditions of Chingaza páramo. [ABSTRACT FROM AUTHOR]

This contribution shows the need to quantify the uncertainty in the wave propagation modelling, a technique frequently used in coastal engineering projects. The magnitude and variability of the errors in estimates of the significant wave height and the energetic wave period was evaluated using modelling and measurements. The modelling of significant wave heights showed mean absolute relative errors between 8% and 14% with respect to measurements depending on which model and deep water wave boundary conditions (buoy measurements or hindcasting) were used. A more detailed analysis indicated that when hindcast data was used, mean errors reached up to 28%, and that for the highest wave heights (Hm0 > 3 m) the confidence decreased finding that the 95% approximate level for the absolute relative error reached up to 40%. Modelled energetic wave periods were generally over estimated and mean errors increased up to 34% when hindcast deep water wave data was used. The level of uncertainty found in this study indicate that in Chile it is necessary to have a long term wave database and a quantification of the accuracy in measurements and wave studies for wave power availability and coastal design assessments. [ABSTRACT FROM AUTHOR]

Based on previous studies about hunting and estimated White-tailed deer population Odocoileus virginianus in Casanare Colombia, the present research proposes a model of deer population dynamics in order to simulate its changes in Colombian Orinoquia. Data generated in Casanare's previous research and bibliographies consulted were used to design the model. Vensim PLE was used to run the simulation and the results show, taking into consideration three possible settings, that: a) the tendency of deer population decreases to extinction, or b) the tendency increases within ten years depending on the availability of vegetal biomass and the intensity of hunting. It is proposed the importance of regulate the intensity of hunting even with high availability of biomass conditions. [ABSTRACT FROM AUTHOR]

The research try to analyse the Corporate Social Responsibility (CSR) based on a model of Compensatory Fuzzy Logic (CFL) in companies that apply the Entrepreneurial Improvement (EI). The CFL allows modelling the knowledge of the predicates correlated to the CSR concept by looking for the continuous refinement of the Management System in terms of the supplies detected in the entities studied. An analysis was executed to 55 enterprises, being visible the work in the economical dimension, not behaving match in the social and environmental dimensions. The model based CFL of the CSR allows when it counts on imprecise knowledge to contribute to the decision-making process in terms of integration and the enhancement of the systems; the majority of the enterprises analysed reflect behaviour of Cuban efficient enterprise in a state 3 of the CSR associated to the Innovation. [ABSTRACT FROM AUTHOR]

A quantitative treatment for texture - properties relationship in so-called Aurivillius ferroelectric ceramics is exposed. The applied general formalism is that of texture analysis through orientation distribution functions and inverse pole figures, Bunge´s formalism, adapted to coupling phenomena. General tools are described and applied to cases representative of real situations. Tensor and surface representations of representative monocrystals´ polarization density, dielectric constant, electrical conductivity and piezoelectric modulus are given. A summary of Quantitative Textures Analysis basic formalisms is presented, with emphasis on polycrystal physical properties calculations. The peculiarities of the texture -ferroelectricity relationship are discussed. Specific algorithms for the calculation of remanent polarization, dielectric constant, electric conductivity and piezoelectric modulus in textured Aurivillius-type polycrystals are provided. Examples associated with typical situations from experimental practice are illustrated. A real case from the literature is characterized quantitatively: Polycrystalline conductivity is theoretically obtained from monocrystal measured data. Calculated and measured results agree satisfactorily.Se expone un tratamiento cuantitativo para la relación textura-propiedades en cerámicas ferroeléctricas tipo Aurivillius. El formalismo general aplicado es el de análisis de texturas a través de funciones de distribución de orientaciones y figuras inversas de polos, tratamiento de Bunge, adaptado a fenómenos de acoplamiento. Se describen las herramientas en general y se aplican a casos representativos de situaciones reales. Se plantean las representaciones tensorial y superficial de las propiedades densidad de polarización, constante dieléctrica, conductividad eléctrica y módulo de piezoelectricidad para monocristales representativos de la familia de materiales considerados. Se presenta un resumen de los formalismos básicos del Análisis Cuantitativo de Texturas, con hincapié en el cálculo de propiedades físicas de policristales. Se discuten las peculiaridades de la relación textura-ferroelectricidad. Se aportan algoritmos específicos para el cálculo de polarización remanente, constante dieléctrica, conductividad eléctrica y módulo piezoeléctrico en policristales tipo Aurivillius texturados. Se dan ejemplos asociados a situaciones típicas de la práctica experimental. Se caracteriza cuantitativamente un caso real de la literatura: a partir de datos monocristalinos se predice la conductividad policristalina. Los resultados calculados coinciden satisfactoriamente con los medidos.

This article shows the research results on the Taylor series' resignification of the movement modeling situation (M-MS). From an epistemological perspective, the usual mathematical discourse does not take into consideration the functional aspect of the Taylor Series. In the wake of Newton's work, this perspective points out how prediction forms the Taylor series. The main axes are prediction and binomial modelling-use of graphs when it comes to a social practice environment. These are the ones that build knowledge and resignificate the Taylor series. [ABSTRACT FROM AUTHOR]

Particulate soil organic carbon (POC) is sensitive to management changes, and a good soil health indicator. However, its determination is tedious and time consuming. Given POC changes represent most of total organic carbon (TOC) variation due to soil use, we hypothesized that POC can be estimated through the variation of TOC. Our objective was to evaluate changes of POC and TOC for a wide range of soil silt (Si) + clay (Cy) contents to assess the feasibility of estimating POC through TOC. Soil samples (n=161) were collected from the surface layer of fields under no tillage throughout the Argentinean Pampean Region, and their TOC and POC concentrations were determined. The variation of POC was described with exponential models fitted as a function of both TOC and TOC/(Si+Cy). The models fitted adequately and estimated POC as a function of TOC (R²=0,96, observed vs estimated not different from the 1:1 line). No improvement was observed when POC and TOC contents were relativized to Si+Cy contents (R²=0,97). Approximately 74% of the estimated values of POC deviated less than ±10% from the observed values. W e conclude that for the conditions studied, the model acceptably estimated POC knowing TOC hence saving time and resources to assess soil health status. [ABSTRACT FROM AUTHOR]

Seed and peel drying by hot air was made at 50, 60, and 70ºC by a tray dryer at lab scale with discontinuous operation. Two models were employed for describing the drying kinetic: a phenomenological model based on Fick's law and an empirical model corresponding to the Peleg's model. So much in the drying of the seeds like in that of the peels, only one diffusive period was observed in the range of the investigated temperatures. It was showed that the external resistance to the mass transfer was negligible to the work condititions. Both diffusive and Peleg models were adequate for describing the drying kinetic of tomato peel and seed. [ABSTRACT FROM AUTHOR]

The Araguari River basin has a huge water resource potential. However, population and industrial growth have generated numerous private and collective conflicts of interest in the multiple uses of water, resulting in the need for integrated management of water quantity and quality at the basin scale. This study used the AQUATOOL Decision Support System. The water balance performed by the SIMGES module for the period of October 2006 to September 2011 provided a good representation of the reality of this basin. The parameters studied were dissolved oxygen, biochemical oxygen demand, organic nitrogen, ammonia, nitrate and total phosphorus. The coefficients of biochemical reactions, sedimentation rates and sediment dissolved oxygen release for this period were calibrated and validated in the quality modeling using the GESCAL module. A sensitivity analysis indicated that the coefficients of carbonaceous matter decomposition, nitrification, water temperature, and sediment oxygen demand interfered more significantly in the variables of state. To prevent eutrophication in the Nova Ponte reservoir and in the other cascade reservoirs, the local River Basin Committee should adopt restrictive actions against the use of agricultural fertilizers. On the other hand, in the sub basin of the Uberabinha River, new alternatives for public water supply to the city of Uberlândia and improvements in the treatment efficiency of the main wastewater treatment plant (WWTP) should be proposed, since the biochemical oxygen demand, ammonia and total phosphorus failed to meet the requirements of COP AM (2008) in the driest months. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Arquitectura (1657-0308) is the property of Universidad Catolica de Columbia, Facultad de Arquitectura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

El análisis estadístico de valores extremos es de suma importancia en muchos campos de la ingeniería.Este trabajo es una breve introducción a la modelación con distribución de valores extremos. Consisteen la presentación de dos métodos básicos comúnmente empleados en el modelado de valores extremospara analizar el problema típico de estimación de valores de retorno. Como ilustración de los métodos,se investiga un conjunto de datos de la precipitación mensual en La Habana. Statistical analysis of extreme values is of importance in many fields of engineering. This paper willserve as a brief introduction to modelling with extreme-value distributions. A presentation of two common,basic methods is given to analyse the standard problem in extreme-value modelling of estimation of returnvalues. As an illustration of the methods, a data set of monthly precipitation at Havana is investigated.

The use of the membrane bioreactors (MBR) has gained an important place in the treatment of urban and industrial wastewater in the last years, due mainly to their advantages over conventional processes of wastewater treatment, such as: higher quality of treated water, less environmental impact if compare with other processes, and better process control. In this work, an analysis of the modelling evolution of such complex systems is presented. The advances in last years in modeling biological and filtration systems in MBR are discussed. The importance of Computational Fluids Dynamics in the study of systems functioning, specifically in the modelling of membrane fouling process is underlined. The current trend to use models that integrate biological degradation with the hydrodynamic and membrane filtration process, achieving a more phenomenological description of the MBR functioning is explained. Finally, the importance of integrated models in the optimization of the MBR functioning with a considerable saving of resources and time is described. [ABSTRACT FROM AUTHOR]

To better understand the potential distribution of Taxus globosa Schlecht., we used a conifer species with restricted distribution, listed on the NOM-059-SEMARN AT-2010, a modeling distribution procedure of maximum entropy or MaxEnt, based on 40 occurrences of field records and 39 REMIB -CONABIO records. Two different scenarios of geographical and environmental coverages--climatic and topographic--were proved statistically. The BIOCLIM variables scenario with topography data show a more accurate model in the range of 0.9 to 1.0 probability with a 55% coincidence; it was statistically significant at (AUC=0.985). Slope variable indicates an environmental variable with more influence in potential modeling, followed by Bio14 (Precipitation of Driest Month). In agreement with the MaxEnt analysis with 19 BIOCLIM and 3 topographic variables, the main plant communities in the modeling area (where Taxus globosa is distributed in Mexico) are pine-oak forest, oak-pine forest, pine forest, and cloud mesic forest. Taxus globosa is potentially distributed in Hidalgo, Nuevo León, Puebla, Tamaulipas, and Veracruz. [ABSTRACT FROM AUTHOR]

This paper presents the results of a research project entitled "Simas Y FreeStyler: La Representacion Del Conocimiento Como Medio Para La Gestion Del Aprendizaje Autónomo "funded by the UNAD and UDI. It is assumed that the creation of learning communities among researchers, educators and students, supported by digital environments is an alternative for improving the quality of education and ensure the inclusion of IT. This paper presents the results of a descriptive research exercise which incorporates tools for the representation and evaluation in solving case studie by group of tenth grade students. The results show that there are effects of these tools on students' abilities to solve challenges commonly faced otherwise. It was noticed the Value that social networks can have when forming learning communities. [ABSTRACT FROM AUTHOR]

Copyright of Dearq is the property of Universidad de los Andes and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The papaya (Carica papaya L.) is a main irrigated fruit crop in Cuba and in the tropical and subtropical regions. For environmental and irrigation management purposes, it is important to accurately estimate its crop evapotranspiration and irrigation requirements. The objective of the present study is to determine the crop coefficients (Kc) and the depletion fraction for no stress (p) of the papaya, variety Maradol, as cultivated in southern Havana. Experiments took place during the period March -- November, 1997 in an experimental area where soils are compacted red iron soils. The ISAREG irrigation simulation model was applied to those observed data. The calibration of the model consisted in searching the crop coefficients and the depletion fraction for no stress that minimize the differences between observed and simulated available soil water. Several statistical indicators were used to assess the goodness of fit. Results show a good adjustment between observations and model predictions, with the regression coefficient forced to the origin close to 1 (b = 1,01) and a high R² = 0,86. The root mean square error (RMSE) and the average absolute error (AAE) are small, respectively RMSE = 6,5 mm and AAE = 4,9 mm. After calibration, the model was used to assess the current irrigation scheduling; results show that irrigation dates were anticipated relative to the required and irrigation depths were excessive, thus a large percolation occurred. The ISAREG model will be further used to generate and evaluate alternative irrigation schedules aimed at improved water productivity. [ABSTRACT FROM AUTHOR]

The geologic risk management is a process which requires to be updated about recent models of technological innovation. It is today necessary to build a specific model for geologic risk management which includes the characteristics of civil construction systems and allows the direct use of tools like GIS, matrices, cost-benefit analysis, etc., oriented to organize and control the knowledge management and termination quality of executed constructions. Modeling with process management could be an interesting alternative with such objective, therefore, this work introduces an option for modeling geologic risk management in the construction and infrastructure processes using the process management methodology. [ABSTRACT FROM AUTHOR]

Copyright of Ingeniería de Recursos Naturales y del Ambiente is the property of Universidad del Valle and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales is the property of Academia Colombiana de Ciencias Exactas, Fisicas y Naturales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An accurate calculation of lightning overvoltages is an important issue for the analysis and design of overhead transmission lines. The different parts of a transmission line that are involved in lightning calculations must be represented taking into account the frequency ranges of transients associated to lightning. In addition, the procedures to be used in these calculations must be developed considering the random nature of lightning phenomena. Several simulation tools have been used to estimate the lightning performance of transmission lines. The most popular approaches are those based on a time-domain simulation technique for which adequate procedures and transmission line models have to be developed. This paper presents a summary of the computational efforts made by the authors for the development and implementation in an EMTP-like tool of a Monte Carlo procedure, as well as the models of some transmission line components, aimed at analyzing the lightning performance of transmission lines. An actual test line is used to illustrate the scope of this procedure and the type of studies that can be performed. [ABSTRACT FROM AUTHOR]

In the nickel industry using Caron technology, the screw conveyors of the lateritic mineral transport facilities suffers frequent breaks. To determine the breaking mechanism of tubes was carried out the simulation and modelling of pipes with circular holes of different inner/outer diameter relationships with the aim of knowing the answer in the stresses domain. Two variants were analyzed: rectangular hole of rounded ends and elliptic hole. It was observed that the stresses increase linearly when the diameter of the hole is increased and the maximum shear stresses are located in the stress concentration. It was found that, in both variants, the crack that causes the break begins in the inner part of the holes to the biggest inner/outer diameter relationships as well as in those places where the stress concentration is bigger. [ABSTRACT FROM AUTHOR]

The modelling of industrial systems is a very hard task because of both the number and diversity of parameters to take into account, and the complex relations between these parameters. In this paper, we are interested on the study of a fully automated Integrated Circuit (IC) semiconductor manufacturing plant (lab). In the semiconductor literature, lab behaviour analysis has very often been performed using discrete-event simulation models, but little work has been devoted to the conceptualisation of the modelling approach. Other works focus on the analysis of single parts of the lab, by simplifying the relations between its components. In such a context, the aim of this paper is to use formal methodologies to model all the components of a wafer lab, that is, its physical and control systems, as well as the fabrication process. This model specification can then be used to build a simulation model for the dynamic factory behaviour analysis. [ABSTRACT FROM AUTHOR]

Based on the results obtained in didactic research on the process of scientific model constructions in the classroom, this paper examines the consequences of this process regarding the interactions that the didactics of modelling would generate, given the change introduced by modelling as an emerging intentionality in scientific education. Regarding the construction of models in the classroom, it is specified that the corresponding didactic work is focused on the ones agreed upon by the respective community of specialists. [ABSTRACT FROM AUTHOR]

The solar drying of wood is modeled according to experimental data informed by Berriz. The current importance of determining the profiles of temperature in wooden samples subjected to the drying is inferred from several authors' publications. The transitory conduction of the heat is intended as the predominant way in the drying process, and the models of Fourier-Kirchhoff and Grever-Likov like solution. [ABSTRACT FROM AUTHOR]

The analysis and calculation of the loads generated in the shafts supports of the rotational machines, is a complex but indispensable process in the task of selection rolling bearings. The present paper exposes the use of the NTIC like effective tools of design and modelling in order to solve this problem. The worm gear transmission case is studied in this investigation because their importance in the industrial machinery and other fields, the analysis of the operation and reaction loads has been formalized in three models. Also it is presented the results of software for calculation, using the information package that contains the three models for obtaining an agile and exact answer of the resulting reaction loads in the shafts supports. [ABSTRACT FROM AUTHOR]