bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating mass public-transport systems
Authors: Ortíz Triviño Jorge Eduardo , Serrano Rivera Luz Ángela
Published: August 2022

A simulation model for evaluating the performance of a mass public-transport system (MPTS) is presented in this report. The final prototype was flexible both for constructing an STPM "skeleton" and modelling random events characteristic of this type of system. The final model was a queuing network with other elements such as origin-destination matrices and graphs allowing typical MPTS phenomena to be considered. The simulation model reacted as expected to changes in the parameters and allowed defining and evaluating typical performance measurement for queues (e.g. mean time spent in the system and queue, expected queue length) as well as others representative of these systems.
Advanced techniques for evaluating instream flows in sustainable watershed management
Authors: Diez Hernández Juan Manuel , Burbano Burbano Liliana
Published: August 2022

Rivers’ potential for satisfying growing water demands has always fascinated human beings. The current idea that a river's natural flow should be reserved to conserve pristine dynamics is a utopian ideal, at least in countries having established a certain level of progress. Effective watershed planning is characterised by being rational and ecological, employing management based on environmental flows (EF), combining water use and ensuring acceptable ecosystem conditions. This work addresses the environmental consequences of regulating rivers and focuses on the need to fix IFs to protect fluvial systems’ ecological integrity. The methods for calculating instream flows are presented as well as approaches provisionally specified in Colombia's legislative framework. Instream flow incremental methodology (IFIM), which is widely used around the world, is summarised to provide a basis for developing a procedure for determining IFs in Colombia as it would seem applicable to local streams. IFIM basic operative rules are then summed up, as is the procedure optimising the balance between a conventional instream flow study's costs and reliability.
X3d2pov. Traductor of X3D to POV-Ray
Authors: Castellanos Mendoza Andrea , Ahogado Diego Alfonso , Charalambos Jean Pierre
Published: August 2022

High-quality and low-quality interactive graphics represent two different approaches to computer graphics' 3D object representation. The former is mainly used to produce high computational cost movie animation.
The latter is used for producing interactive scenes as part of virtual reality environments. Many file format specifications have appeared to satisfy underlying model needs; POV-ray (persistence of vision) is an open source specification for rendering photorealistic images with the ray tracer algorithm and X3D (extendable 3D) as the VRML successor standard for producing web virtual-reality environments written in XML. X3d2pov has been introduced to render high-quality images from an X3D scene specification; it is a grammar translator tool from X3D code to POV-ray code.
Behavior of cold-formed thin steel sections (MM) under concentrated loads
Authors: Molina Herrera Maritzabel , Ortíz Porras Javier Alberto
Published: August 2022

New sections are continually being developed in the cold-formed steel world to improve the performance of existing sections. M-section development provides an example of improving C-sections’ shear resistance and web crippling resistance against C-sections’ concentrated loads. C-sections’ shear nominal strength can be achieved through locating tow web intermediate stiffeners (M-sections) even though web crippling resistance cannot be increased in the same way. Such intermediate stiffeners mean that M-section stresses and deflections cannot be analysed with traditional material mechanics. Concentrated loads cause this behavior to become increased; 4 different models and 3 tests for each of them were thus developed, as well as determining M-sections’ theoretical resistance (based on 1996 AISI). The values obtained corresponded to maximum resistance load, visual identification of any possible type of failure, deflections (at middle span) and deformations (εx, εy, εxy). Mathematical models were also used for comparing the finite element method and simplified mathematical models’ test results for a detailed review of MM-section stress and deformation. These models were calibrated on the test results. After the failure mode was identified for each model, MM-section maximum resistance load was compared to nominal load (according to AISI formulation, also aiding formulating nominal strength calculation). The information obtained from tests and mathematical models was analysed to observe parameter (∆, σ y T) tendencies respecting applied load (P). Cyclic tests under pseudo-static loads were performed to study MM-sections’ hysteretic behavior.
Square pulse current wave’s effect on electroplated nickel hardness
Authors: Hoyos Bibian Alonso , Ossa Luis Alberto , Rendón Monica Cecilia
Published: August 2022

The effects of frequency, average current density and duty cycle on the hardness of electroplated nickel were studied in Watts and sulphamate solutions by means of direct and square pulse current. The results in Watts’ solutions revealed greater hardness at low duty cycle, high average current density and high square pulse current frequency. There was little variation in hardness in nickel sulphamate solutions to changes in duty cycle and wave frequency. Hardness values obtained in the Watts’ bath with square pulse current were higher than those achieved with direct current at the same average current density; such difference was not significant in sulphamate bath treatment.
Model for supporting awareness in the CSCL ALLEGRO environment through a blackboard architecture
Authors: Ovalle Carranza Demetrio Arturo , Jiménez Builes Jovani Alberto , Collazos Ordóñez César Alberto
Published: August 2022

This paper is aimed at describing collaborative activities, the awareness process and blackboard architecture used within the ALLEGRO system, a multi-agent learning and teaching environment which has included artificial intelligence mechanisms (instructional planning (IP), cased-based reasoning (CBR), multi-agent systems (MAS), intelligent tutoring systems (ITS) and computer supported collaborative learning (CSCL)). The proposed model of awareness promotes communication, collaboration and coordination in CSCL ALLEGRO. MAS-CommonKADS methodology was applied for building the Multi-Agent system. ALLEGRO based its instructional approach on the following three pedagogical paradigms: conductive behavior, cognitive mechanisms (distributed cognition and problem-based learning) and social-historical theory. The system was validated via several case studies regarding the graphical digital domain for postgraduate architectural studies. The proposed awareness model lets students develop important skills such as conscious behavior, communication, collaboration and coordination in the CSCL component of the ALLEGRO system. This model facilitates students acquiring a perception of what others are doing inside the CSCL, thereby using such knowledge for interacting with the environment and developing leading to expressing and exchanging ideas and opinions with other students, transforming the class into an open virtual forum for reflection, proactive interaction and a critical space for exchanging ideas. The proposed instructional model is a valuable resource from the technological and pedagogical point of view as different theories are integrated, some of them conflicting with others.
Using ANFIS networks and current signals for locating faults in power distribution systems
Authors: Mora Flórez Juan José , Pérez Hernández Lucas Paúl , Pérez Londoño Sandra Milena
Published: August 2022

Fault location in power distribution systems is very important because of power service continuity requirements, mainly imposed by current electricity market quality standards. A fault location approach is adopted in this paper using current waveforms as measured at electricity substations, knowledge of protection-device settings and ANFIS networks. Good results were obtained from tests carried out in a prototype power distribution system to locate where faults were occurring. These results revealed variation in fault-locator precision due to using different current signal characteristics or descriptors. An error lower than 1% was obtained in the best case. Two more alternatives are also presented where errors were lower than 4%; such results validate the approach presented here.
Feature selection using a genetic algorithm-based hybrid approach
Authors: Giraldo Luis Felipe , Trejos Edilson Delgado , Riaño Juan Carlos , Castellanos Domínguez Germán
Published: August 2022

The present work proposes a hybrid feature selection model aimed at reducing training time whilst maintaining classification accuracy. The model includes adjusting a decision tree for producing feature subsets. Such subsets’ statistical relevance was evaluated from their resulting classification error. Evaluation involved using the k-nearest neighbors’ rule. Dimension reduction techniques usually assume an element of error; however, the hybrid selection model was tuned by means of genetic algorithms in this work. They simultaneously minimise the number of features and training error. Contrasting with conventional methods, this model also led to quantifying the relevance of each training set’s features. The model was tested on speech signals (hypernasality classification) and ECG identification (ischemic cardiopathy). In the case of speech signals, the database consisted of 90 children (45 recordings per sample); the ECG database had 100 electrocardiograph records (50 recordings per sample). Results showed average reduction rates of up to 88%, classification error being less than 6%.
Fault diagnosis with neural networks. Part 1: Trajectory recognition
Authors: Tarifa Enrique Eduardo , Martínez Sergio Luis
Published: August 2022

The present investigation was focused on formulating a method for designing a fault diagnosis system for chemical plants by using artificial neural networks. Fault diagnosis is aimed at identifying a fault which affects a given process by analysing the signs supplied by process sensors. Neuronal networks are mathematical models which try to imitate the functioning of the human brain. A neural network is defined by its structure and the learning method used. The difficulty with diagnosing faults lies in recognising the trajectories (temporal series of data) followed by process variables when a fault affects the process; when trajectories are recognised, the associated fault is also identified. The theory so developed recommended an optimised structure and training method for the neural networks to use. Both the proposed structure and the training method were tested by carrying out comparative studies between traditional structures and a training method. The results showed the superiority of the neural networks designed and trained with the method proposed in this work. Except for simple processes, fault diagnosis is a more complex problem than simply identifying trajectories, because a fault may cause an infinite set of trajectories (i.e. flow). The fundaments established in this work are thus used in Part Il, where the analysis is extended to recognise flows.
Severe plastic deformation for obtaining nanometric and ultrafine-grained materials
Authors: Rodríguez Baracaldo Rodolfo , Benito Páramo Jose Antonio , Cabrera Marrero José María
Published: August 2022

The aim of this paper is to provide a general overview of nanocrystalline and ultra-fine grain material production using severe plastic deformation (SPD), this being one of the most active research fields in the mechanical processing of materials. The paper gives an explanation of the more important SPD techniques (mechanical milling, equal channel angular pressing, high pressure torsion, extrusion-compression and accumulated roll-bond) as regards fundamental principles, advantages and limitations. Some experimental results for iron and copper obtained by this paper’s authors are attached. These materials’ great potential is shown in several fields of use, especially in the aerospace industry. Current research prospects are also referred to in terms of structural and mechanical behavior and the development of large-scale industrial processing.
A comparative analysis of calculating sample size for carrying out household surveys when constructing a passenger origin-destiny matrix between a sample design and applying a population percentage
Authors: Flórez Valero Carlos Fabián , González Rodríguez Rafael Alberto
Published: August 2022

Using a percentage of a city’s households is a common practice in transport engineering leading to knowing the inhabitants’ journey pattern. The procedure theoretically consists of calculating the sample based on the statistical parameters of population variable which one wishes to measure. This requires carrying out a pilot survey which cannot be done in countries having few resources because of the costs involved in knowing the value of such population parameters, because resources are sometimes exclusively destined to making an estimated sample according to a pre-established percentage. Percentages between 3% and 6% are usually used in Colombian cities, depending on population size.
The city of Manizales (located 300 km to the west of Colombia’s capital) carried out two household surveys in less than four years; when the second survey was carried out the values of the estimator parameters were thus already known. The Manizales’ mayor’s office made an agreement with the Universidad Nacional de Colombia for drawing up the new origin-destiny matrix, where it was possible to calculate the sample based on the pertinent statistical variables. The article makes a comparative analysis of both methodologies, concluding that when statistically estimating the sample it is possible to greatly reduce the number of surveys to be carried out, but obtaining practically equal results.
Using multi-criteria decision-making for selecting broad-band technology for the National University of Colombia, Bogotá
Authors: Cortés Aldana Félix Antonio , García Melón Mónica , Aragonés Beltrán Pablo
Published: August 2022

The National University of Colombia, Bogotá, has proposed a project for improving Internet access by using broad band technology. Four possible technologies have been selected in the first step: LMDS, ADSL, cable modem and optical fiber. The analytic hierarchy process (AHP) has been applied for taking such decision. This method, based on multi criteria decision analysis (MCDA) allows decision-taking criteria to be established, pondered and the alternatives evaluated regarding the priorities established for each criterion. Different experts’ opinions have been considered as support during the decision-making process. MCDA was used for ranking these alternatives. AHP was used for helping such decision-making.
Using the critical impedance method for determining the dominant harmonic source in medium voltage circuits
Authors: García M. Pável Julián , Rodríguez E. Lucien A. , Rojas Herbert E. , Ríos Carlos Alberto
Published: August 2022

Automating industrial processes has led to the distortion of current and voltage waveforms, causing harmonic contamination in distribution networks. This paper shows the application of a practical methodology which determines the dominant harmonic source at the point of common coupling (PCC) between the network operator (NO) and the client. This is known as the critical impedance (CI) method, requiring monitoring voltage, current and phase angle signals for each existing harmonic component and NO and client Thevenin impedance values seen in PCC. The method needs approximate impedance information to operate and a simple and structured mathematical analysis based on studying the measurements projecting a useful, reliable and practical solution for detecting the dominant harmonic source in distribution systems.
Metaheuristics applied to vehicle routing. A case study. Part 2: genetic algorithm, compared to a heuristics solution
Authors: González Vargas Guillermo , González Aristizábal Felipe
Published: August 2022

This paper presents a solution to a vehicle-routing problem by using two different techniques. In the first instance, a genetic algorithm was applied (different experiments were done); later on the cluster first-route second methodology was used via heuristic sweep and local search, respectively. The results of the different techniques were then compared.
A predictive model of natural gas mixture combustion in internal combustion engines
Authors: Espinoza Henry , Patiño Luís , González Yordy , Irving Lezama
Published: August 2022

This study shows the development of a predictive natural gas mixture combustion model for conventional combustion (ignition) engines. The model was based on resolving two areas; one having unburned combustion mixture and another having combustion products. Energy and matter conservation equations were solved for each crankshaft turn angle for each area. Nonlinear differential equations for each phase’s energy (considering compression, combustion and expansion) were solved by applying the fourth-order Runge-Kutta method. The model also enabled studying different natural gas components’ composition and evaluating combustion in the presence of dry and humid air. Validation results are shown with experimental data, demonstrating the software’s precision and accuracy in the results so produced. The results showed cylinder pressure, unburned and burned mixture temperature, burned mass fraction and combustion reaction heat for the engine being modelled using a natural gas mixture.
The impact of freeze-drying on strawberry quality
Authors: Amrani Mahacine , Brigui Jamal
Published: August 2022

This work analyses and models the dehydration kinetics for whole and sliced strawberries during freeze-drying.
A Virtis 35L Gardiner lyophyliser was used. Freeze-drying was carried out at various hotplate temperatures and several product thicknesses. It was observed that increasing hotplate temperature from 30°C to 70°C during the course of freeze-drying led to reducing the process from 48h to 36h for whole strawberries and from 12h to 8h for the slices, stable dry products being obtained. Studying several strawberry freeze-drying parameters showed that temperature has an important effect on reducing the process’ duration. It lowers the process’ cost whilst preserving dry fruit quality, thereby opening up the field by applying this technology to treating new food products.
SIM parameter-based security for mobile e-commerce settings
Authors: Martínez Pabón Francisco Orlando , Caicedo Guerrero Jaime , Hernández Cuenca Rodrigo , Caicedo Rendón Oscar Mauricio , Hurtado Guaca Javier Alexander
Published: August 2022

Security requirements are more demanding in the e-commerce domain. However, mobile e-commerce settings not only insist on security requirements, they also require balance between security levels and hardware and usability device ability. These features require designing models having simple authentication and authorisation scheme which also ensures information integrity for each e-transaction. The Mobile and Wireless Applications’ Development Interest Group W@Pcolombia thus developed the P3SIM platform so that mobile applications might include SIM parameter-based security features. The P3SIM platform’s framework and compilation and simulation settings combines the advantages of identification provided by the SIM module with the security features provided by SATSA and Java Card APIs for Java ME environments, one of the most-used platforms for mobile application development. Developing an m-commerce-based prototype not only shows the platform's ability to operate in secure environments, it also shows its ability to comply with environmental security requirements.
Nonlinear material influence on reinforced concrete beams’ immediate deflections
Authors: Gómez Cassab Alexander , Lizarazo Marriaga Juan Manuel
Published: August 2022

This paper presents an analytical and experimental research programme’s results regarding material nonlinearity’s influence on reinforced concrete beams’ immediate deflections. Six full-size laboratory beams were tested under different type of loads in the experimental programme. The ANSYS finite element software nonlinear material model was used for simulating the beams’ analytical behavior. Comparing ANSYS nonlinear material model results, ACI 318 equations and the results of the tests made revealed that a beam’s structural behavior is strongly influenced by material nonlinearity.
Evaluating Colombian SMEs’ technological innovation. Part 2: problems and challenges in innovation
Authors: Torres Luz Marina , Castellanos Domínguez Óscar Fernando , Salgado César Alberto
Published: August 2022

As innovation is an extremely important aspect of economic progress, then new technologies and improving existing ones must be evaluated for establishing the state of innovative culture and the ability to develop technology. The Colombian Innova award for Entrepreneurial Technological Innovation for SMEs was created in 2004, aimed at motivating technological and innovative development in this type of company. It also represents an important state initiative for promoting entrepreneurial innovation, providing a valuable source of information for establishing mechanisms for producing innovation in companies and gauging the current state of Colombian SMEs regarding innovation. This article outlines the structure of the award value chain, following-up and analysing the award’s results, understanding how it is awarded and identifying the actors involved in it. Analysing the award value chain led to identifying the lack of coordination between the National Innovation System (NIS) and companies and establishing participants and award-winners’ geographical and sector distribution (contrasts being found between cities such as Bogotá, Medellín and Cali). The characteristics of processes leading to promoting innovation in participating companies (in most cases developing their innovative products or processes in completely organisationally endogenous contexts) were thus identified. These results (providing valuable information for strengthening the award) also provided important input for strengthening strategies for promoting innovation in Colombian SMEs.
Evaluating hydrogels for agriforestry applications
Authors: Barón Cortés Andrés , Barrera Ramírez Ingrid Xiomara , Boada Eslava Luis Francisco , Rodríguez Niño Gerardo
Published: August 2022

Hydrogels synthesised by inverse suspension polymerisation (ISP) technique consisting of acrylamide and potassium acrylate interlinked with N, N’ methylene-bis-acrylamide and presenting different behavior in terms of rooting ability and speed, elastic module and release properties were studied. Markedly clayey soil properties were modified by drawing up moisture-retention curves using ceramic plate pressure waves and developing montages for evaluating modifications made to their retention, regarding prolonged and instantaneous irrigation-water dosage conditions. Acacia and radish crops were grown in nursery phase in soil conditioned with different hydrogels.
Delayed specie withering was simultaneously evaluated in the first crop and difference in growth in the second one. Follow-up of in situ soil moisture content was also evaluated over a fixed period of time. A method was achieved for measuring elastic module and release properties and model was established for predicting hydrogel behavior in soil having known basic properties in free state. The results revealed the usefulness of hydrogels in such applications: greater facility in usable water release and retention by soil, notable delay in withering in hostile conditions and greater growth of species. Guidelines were also established for defining the characteristics of hydrogel more adequately, depending on the desired application and a projection was made concerning reducing water consumption for maintaining a particular crop.
Vitrinite-rich coal concentrate intrinsic reactivity index
Authors: Rojas González Andrés Felipe , Barraza Burgos Juan Manuel , Piñeres Mendoza Jorge Luís
Published: August 2022

This work defines a new reactivity coal combustion parameter called intrinsic reactivity index (IRI), combining reactive maceral fraction (vitrinite/liptinite), non-reactive maceral fraction (inertinite/intrinsic mineral matter) and vitirinite reflectance averages. Coal samples from La Yolanda and Guachinte (Valle del Cauca) collieries were used to evaluate the IRI; samples consisted of original and vitrinite concentrated fractions obtained from froth flotation column. This new parameter was compared to three conventional parameters: weighted mean activation energy (WMAE), peak temperature (PT) and final temperature (FT). Results revealed that vitrinite concentrated fractions had higher IRI figures than original coal. This meant that vitrinite concentrated fractions presented higher reactivity to combustion than original coal. Results also showed that EAMP TP and TF decreased with an increase in IRI, suggesting that coal combustion reactivity becomes improved when vitirinite concentration in coal is increased.
A review of magnetic insulation
Authors: Arévalo Velosa Zósimo , V. Sinitsyn Alexander , Castañeda U. Octavio Alejandro , Camelo B. Miguel Hernando
Published: August 2022

High energy devices are designed to work with extremely high electric and magnetic fields. As a consequence, these devices show non-linear phenomena and behavior, such as magnetic insulation which alters electron trajectory. A mathematical analysis and review of magnetic insulation were carried out as a consequence of nonlinearity to find frontier conditions and solutions to the problem. This paper was aimed at presenting the topic in a way which is easier for that part of the academic community which is unfamiliar with it to understand it. The paper gives a description of the phenomena developed by high electric and magnetic fields in a vacuum plane diode, some equations modelling the phenomenon, proves its existence and finds positive solutions based on upper and lower solutions for boundary limit problems and gives some practical applications.
A business management- and workflow-orientated information system in the Universidad Nacional de Colombia: perspectives and case-study
Authors: Jiménez Olea Ana Paula , Salamanca Rivera Pedro Alexander , Garavito Herrera Luís Antonio
Published: August 2022

This article presents an introduction to a case study concerning the academic secretariat, a dependency of the School of Engineering, Universidad Nacional de Colombia. A methodological approach towards implementing Business management (BM) / Workflow Management System (WMS), using an open source code, aimed at making significant improvements in the School of Engineering’s administrative processes, particularly how teacher's applications are dealt with. This was to optimise the secretariat’s functional performance and create knowledge in this field; general considerations are given. The possible implementation of an integral BPM- and WMS-orientated information system at the academic secretariat (seen as automating key processes) may result in satisfying external and internal clients, through advantages such as reduced cost, waiting time and paperwork, plus improved use of information.
Dimentional welding control using vibratory stress relief
Authors: Casanova García Fernando , Henao Saldarriaga Duván , Franco Arenas Fernando
Published: August 2022

The effectiveness of applying vibratory stress relief to controlling deformations due to internal stresses on plates produced by welding was evaluated in this research. The magnitude of distortion produced in three groups of specimens which had been treated with vibration during and after welding was also evaluated. The specimens consisted of austenitic stainless steel plates which tend to become deformed due to high expansion and shrinkage coefficient and low thermal conductivity during arc welding. Their deformation was quantified by measuring the vertical distance which the end of the plate moved after the welding bead was applied. The magnitude of stress produced by the effect of vibration was measured too. The results revealed a clear reduction of the final deformation in treated specimens compared to non-treated ones. It was also found that the magnitude of stress produced during vibration had no important effect on the treatment’s effectiveness.
Assessing landslide susceptibility by applying fuzzy sets, possibility evidence-based theories
Authors: Chivatá Cárdenas Ibsen
Published: August 2022

A landslide susceptibility model was developed for the city of Manizales, Colombia; landslides have been the city’s main environmental problem. Fuzzy sets and possibility and evidence-based theories were used to construct the model due to the set of circumstances and uncertainty involved in the modelling; uncertainty particularly concerned the lack of representative data and the need for systematically coordinating subjective information. Susceptibility and the uncertainty were estimated via data processing; the model contained data concerning mass vulnerability and uncertainty. Output data was expressed on a map defined by linguistic categories or uncertain labels as having low, medium, high and very high susceptibility; this was considered appropriate for representing susceptibility. A fuzzy spectrum was developed for classifying susceptibility levels according to perception and expert opinion. The model showed levels of susceptibility in the study area, ranging from low to high susceptibility (medium susceptibility being more frequent). This article shows the details concerning systematic data processing by presenting theories and tools regarding uncertainty. The concept of fuzzy parameters is introduced; this is useful in modelling phenomena regarding uncertainty, complexity and nonlinear performance, showing that susceptibility modelling can be feasible. The paper also shows the great convenience of incorporating uncertainty into modelling and decision-making. However, quantifying susceptibility is not suitable when modelling identified uncertainty because incorporating model output information cannot be reduced into exact or real numerical quantities when the nature of the variables is particularly uncertain. The latter concept is applicable to risk assessment.
Implementing technological intelligence systems from the viewpoint of complexity theory
Authors: García Vergara María Elena , Castellanos Domínguez Óscar Fernando , Monroy Varela Sonia Esperanza
Published: August 2022

Technology currently plays a very important role in organisations’ development and competitiveness, thus requiring suitable handling. Technology management has been strengthened by integrating new systematically-applied concepts, such as technological intelligence (TI). The present article was aimed at analysing TI’s conceptual referents and how to implement them. An approach was therefore needed admitting dynamism for producing knowledge (know-how) and using it in production processes. The challenges observed in different contexts were defined for achieving greater efficiency in producing strategic intelligence-supported technology management. Complexity theory was reviewed as this could provide an analytical and conceptual framework for studying systems like those involved in intelligence where interactions form the fundamental aspect for understanding them. This work has led to proposing possible contributions from complexity theory for TI systems, postulating considerations for making them more dynamic.
Experimental evaluation of a spark-ignited engine using biogas as fuel
Authors: Mantilla González Juan Miguel , Aguirre Junco Borys Javier , Sarmiento Pinilla Luis Andres
Published: August 2022

Different CH4 and CO2 mixtures were used as fuel in this work; they were fed into a spark-ignited engine equipped with devices allowing spark advance, gas delivery and gas consumption to be measured. Engine bench-tests revealed changes in the main operation parameters and emissions. The results showed that increasing CO2 percentage in the mixture increased the spark angle, reduced maximum power and torque and reduced exhaust emissions (by 90% in some cases) when DAMA resolution 1015/2005 was applied. The main components to be considered when an engine of this type operates with gas fuel were also recognised.
A model for assessing information technology effectiveness in the business environment
Authors: Riascos Erazo Sandra Cristina
Published: August 2022

The impact of technology on administrative processes has improved business strategies (especially regarding the effect of information technology - IT), often leading to organisational success. Its effectiveness in this environment was thus modelled due to such importance; this paper describes studying a series of models aimed at assessing IT, its advantages and disadvantages. A model is proposed involving different aspects for an integral assessment of IT effectiveness and considering administrative activities’ particular characteristics. This analytical study provides guidelines for identifying IT effectiveness in a business environment and current key strategies in technological innovation. This study was based on ISO 9126, ISO 9001, ISO 15939 and ISO 25000 standards as well as COBIT and CMM standards.
Determining heat transfer coefficients in radial flow through a polyethylene packed bed
Authors: Patiño Luís , González Yordy , Carmona Antonio , Valero José , Espinoza Henry
Published: August 2022

A numerical-experimental methodology was used for determining interstitial heat transfer coefficients in water flowing through porous media where it was not in heat balance with the solid phase. Heat transfer coefficients were obtained through the single blow transient test method, combining experimental test equipment results with a mathematical model’s numerical solution. The partial differential equation system produced by the mathematical model was resolved by a numerical finite volume method-based methodology. Experimental tests and numerical solutions were satisfactorily carried out for different values from the fluid’s surface speed from the entrance to the bed and for different porosity values, finding that Nusselt numbers increased when Reynolds numbers also increased and that Nusselt numbers increased when porosity decreased. A 650 Reynolds number and 0.375 porosity gave a Nusselt number of up to 2.8.
Laminated steel and concrete slab composite beam behavior using grade two shear connector screws
Authors: García Zamora Alejandro , Molina Herrera Maritzabel
Published: August 2022

This paper reports using theoretical-experimental analysis for obtaining and characterising the design parameters governing steel and concrete slab composite beams’ behaviour using shear connector screws. Currently no research has been found about such behaviour and Colombian seismic-resistant regulations (NSR-98) have not yet defined such design; these types of connectors are most used in constructing composite sections in Colombia. The results of 36 experimental scale tests for 21MPa and 28MPa concrete strengths were taken for the analysis; each concrete strength had three screw diameters (Ø1/2 ", Ø5/8 " and Ø3/4 ") with 0.10m and 0.30m separations. This research also studied other effects such as slip caused by steel and connector profile deformation or deformation due to concrete degradation. Formulations were thus used which included connector slip and separation.  The article sets out a methodology for designing composite beams using shear connector screws. It also proposes a formulation for calculating connector shear strength, thereby obtaining almost 62% stud connector resistance when separation was 0.10m and an extra 13% for 0.30m separations in elastic parameters where 62% of theoretical effective inertia was obtained and 23% more composite beam average bending strength was found than that required by current regulations.
Modeling of forced vibration phenomenon by making an electrical analogy with ANSYS finite element software
Authors: Pallares Muñoz Myriam Rocío , Rodríguez Calderón Wilson
Published: August 2022

Designing mechanical systems which are submitted to vibration requires calculation methods which are very different to those used in other disciplines because, when this occurs, the magnitude of the forces becomes secondary and the frequency with which the force is repeated becomes the most important aspect. It must be taken care of, given that smaller periodic forces can prompt disasters than greater static forces. The article presents a representative problem regarding systems having forced vibration, the mathematical treatment of differential equations from an electrical and mechanical viewpoint, an electrical analogy, numerical modeling of circuits using ANSYS finite element software, analysis and comparison of numerical modeling results compared to test values, the post-processing of results and conclusions regarding electrical analogy methodology when analysing forced vibration systems.
Evaluating a steel beam’s rigid connection to a concrete filled tubular column when submitted to dynamic load
Authors: Uribe Vallejo Maritza , Valencia Clement Gabriel F.
Published: August 2022

Using prequalified connections during the structural design stage becomes increasingly necessary when developing structural engineering projects which include steel elements; this is so that the steel elements’ appropriate behavior can be ensured according to the structural system and seismic demand. Unfortunately, the international entities providing this type of information (i.e. FEMA) only have a limit series of prequalified connections and such series do not include rigid connections between steel beams and concrete filled tubular (CFT) columns having an extended end plate, which has become a very widespread building practice in Colombia. This paper describes the most important aspects of a study at the Universidad Nacional de Colombia concerning the behavior of a steel beam rigidly connected to a CFT-column, using six physical models having different width-thickness ratio (b/t) columns. ANSYS v.10 software was used for studying theoretical models (finite elements analysis) for comparative analysis of cyclic test theoretical and experimental results for each specimen presented for the qualification phase. The six tested specimens’ hysteretic curves are presented. Several conclusions are drawn concerning finite element validation for this type of connection and the influence of width-thickness ratio (b/t) variation and design recommendations for suitable behavior under dynamic loads when this type of connection was used.
Time series for water levels in virtual gauge stations in the Amazon basin using satellite radar altimetry
Authors: León Hernández Juan Gabriel , Rubiano Mejia Jorge , Vargas Viviana
Published: August 2022

Using satellite altimeter radar technology for monitoring changes in water levels at continental scale is a relatively recent advance. Several studies have demonstrated the interest being shown in applying this technology to monitoring the hydrographic patterns of large-scale basins worldwide. The current study presents the inference of time series representing changes in water level for bodies of water by defining virtual gauge stations deduced for two very different rivers in terms of their biophysical and topographic characteristics; the two rivers were the Rio Negro in the Brazilian Amazon Basin and the Caquetá River on the Colombian side. The differences between the two rivers revealed the limits of satellite radar altimeter when applied to continental waters (±20cm and ±40 cm precision for Río Negro and Río Caquetá, respectively). However, applying this technology seems very promising, since new missions have been scheduled to be put into orbit by the end of 2008.
Implementing a collaborative virtual environment - specification for a usability metamodel
Authors: Villegas R. Maria L. , Hernández A Hamilton A. , Giraldo O. William J.
Published: August 2022

This research presents the results of the first phase of a macro-project for constructing a collaborative virtual environment. It was aimed at selecting a graphical interface from five proposed for such environment, considering each one’s level of usability. Several standards of usability and user-centered design patterns were studied for specifying interface measurment criteria for specifying a usability metamodel; this defined the variables and rules to be taken into account when measuring graphic user interface (GUI) usability level for collaborative virtual environments. The use of metaphors when specifying graphic user interfaces is also briefly looked at as a source of new usability and satisfaction related to such interface use.
Compressive strength and rheology of environmentally-friendly binders
Authors: Lizarazo Marriaga Juan Manuel , Claisse Peter
Published: August 2022

Ordinary Portland cement production accounts for 9% of worldwide greenhouse gas emissions. This paper summarises the results of research aimed at developing environmentally-friendly binders which can be used as an alternative in civil construction, aimed at generating alternatives and sustainable materials. Mixes of the combination of granulated ground blast furnace slag, basic oxygen slag, cement kiln dust and plasterboard gypsum were used for optimising the binders, according to their compressive strength, to obtain 5 concrete mixtures made partially or completely with industrial waste. The results showed that the compressive strength of mixtures of Portland cement and industrial waste were suitable for different civil construction applications and, although mixtures formed entirely from industrial waste had a significant decrease in their compressive strength, the results showed great potential for specific industrial applications. In addition to compressive strength, the rheological properties of these mixtures were determined for defining flow and workability characteristics.
Thermogravimetric characteristics of char obtained at high heat rate
Authors: Rojas González Andrés Felipe , Barraza Burgos Juan Manuel
Published: August 2022

Coal reactivity during combustion is determined by the thermogravimetric characteristics of char. The thermogravimetric characteristics of chars obtained in a droptube furnace were studied in this work. Chars from the devolatilisation of three bituminous coals were obtained at three times (100, 150 and 300 ms), three temperatures (900, 1,000 and 1,100ºC) and at high heat rate (104 K/s). The chars were burned using non-isothermal thermogravimetry (heated to 900ºC) and isothermal thermogravimetry at 700ºC, 800ºC and 900ºC to obtain their combustion profiles. Characteristic temperatures (ignition, peak and final temperatures) were determined by non-isothermal thermogravimetry; it was found that chars from La Yolanda coal gave the highest figures for the characteristic temperatures. Isothermal thermogravimetry revealed that the combustion rate for the three coals decreased with increased devolatilisation time and combustion temperature.
A comparative study of GERIPA ethanol with other fuels
Authors: Lombardi Geraldo , Rodríguez Ramos Pedro A. , Ometto Aldo , Corsini Romeu , Pérez Ones Osney , Zumalacárregui de Cárdenas Lourdes
Published: August 2022

The GERIPA project aimed at generating renewable energy integrated with food production has led to a beneficial option for producing ethanol and electricity. Ethanol has economic, social and environmental potential. Considering just the first one, Brazil consumes 39 billion liters per year-LD/yr of diesel oil, 18% of it being imported. The Federal Government has a recovery programme for the soybean agribusiness aimed at soybean biodiesel (SBD) production in which a 10% addition to diesel has been proposed. This 10% involves producing 10.7 million LSBD/d. Soybean biodiesel production is not self-sustainable and such proposal could require an annual subsidy of up to US$1.33 billion. Soybean plantations would need about 10 to 12 times more land than is necessary for sugarcane plantations to produce the same equivalent thermal energy (ETE). Sixty-seven GERIPA projects (GP) producing 80,000 liters of ethanol per day (GP80) could be set up with the sum of US$1.33 billion; this would substitute current Brazilian biodiesel demand by 4.28%, adding the same value for each new subsidiary. Considering ETE, ethanol-GP cost would be 37% to 50% below that for a liter of SBD on account of its raw material (RM) and region. The diesel cycle's thermal efficiency (ηt) yield is around 50% and that of the Otto cycle engine ηt is around 37%. The cost per km driven (CKD) by substituting SBD for ethanol-GP80 would thus indicate an 18% minimum and 59% maximum cost reduction for vehicle engines.
Studying PW-Amberlite catalyst deactivation in limonene epoxidation by hydrogen peroxide
Authors: Barrera Zapata Rolando , Villa Holguín de P. Aída Luz , Montes de Correa Consuelo
Published: August 2022

The PW-Amberlite catalyst is active for limonene epoxidation in triphasic conditions; it becomes deactivated in reaction conditions. Catalyst stability during the reaction and recovery of catalyst activity when it was treated with several solvents were evaluated. It was found that the catalyst recovered 99% of its initial activity when it was washed with toluene and that the recovery was 95% and 97% when ethanol or acetone were used as washing solvents, respectively. Leaching tests showed that the reaction did not continue when the catalyst was removed from the reaction mixture, confirming the absence of leaching during the catalyst's active phase. FTIR analysis revealed that the characteristic species of the phosphotungstate complex did not vary with successive reusing of the catalyst.
Evaluating a hydraulic classification system for the differential separation of solid mixtures
Authors: Osorio Correa Adriana Marcela , Marín Juan Miguel , Peláez Restrepo Juan Felipe , Restrepo Vásquez Gloria María
Published: August 2022

A hydraulic classification system having four equidistant discharge points for solid mixtures was evaluated using a 23 factorial experimental design for each discharge. The evaluation factors consisted of 0.9 to 2.7 m3/h flow rate, 1,420 to 2,520 Kg/m3 particle density and 0.0005 to 0.002 m particle size. The response variable was the degree of each material's recovery efficiency. Stat Graphics statistical software was used for obtaining the theoretical models, showing higher than 99% correlation between them. The theoretical models were experimentally validated for two cases: classifying different sized material having the same density and classifying materials having equal size but different density. Coal and quartz were the materials used for the model; they were characterised in terms of their propertied as individual particles and as a mass of particles. Size separation was done by sieve (granulometric) analysis. Error percentages were low (0.7% to 14%) in the first experimental case; however, errors in the second case in predicting the separation of heavier material were very high (above 50%), perhaps due to the nature of the material. The above models will form the basis for continuing to study these operating and design variables which in practice determine such processes' dynamic response and operational performance for the ongoing search for optimum operating conditions.