Scientia et Technica

Analysis of the conversion efficiency and THD of DC/AC converters used in off-grid Photovoltaic generation system

Nairo Julian Rodriguez Ballesteros — 2025-06-30

This article presents an experimental analysis of the conversion efficiency and total harmonic distortion (THD) of two DC/AC converter prototypes designed for off-grid photovoltaic generation systems (OPGS). The objective is to determine the influence of two controllable factors; the DC input voltage and the percentage of nominal load at the output, on the converters’ performance. The prototypes, based on unipolar SPWM modulation, were implemented using simulation software, and tested under a factorial experimental design. The study applied statistical methods, including ANOVA, to analyze the effect of each factor and their interaction on the two response variables: efficiency and THD. Results showed that for the first prototype, efficiency is independent of DC input voltage but dependent on load, while THD is influenced by both factors. In the second prototype, both efficiency and THD are affected by variations in both factors, with THD showing instability due to LC network resonance. The comparison reveals that locating the LC filter after the transformer slightly improves THD but reduces efficiency due to increased harmonic losses. These findings are relevant for optimizing inverter design in isolated PV systems.

Mathematical Model for Analyzing the Fluorescence Emission of Biological Tissue

Belarmino Segura Giraldo — 2025-07-23

Optical emission fluorescence spectroscopy allows for determining biochemical changes in normal and pathological biological tissue in-vivo or in biopsies. The aim of the study is to analyze the chemical and physical properties of the cervix tissue. The mathematical model is presented to examine and observe the fluorescence emission of the tissue. In the precancerous state development, the optical properties of the tissue can be altered not only by the light dispersion and the fluorescence increase in the epithelium but for the fluorescence reduction in the stroma. Beer-Lambert Law was used to describe light propagation in the tissues. Four components of cervix tissue were identified: collagen, elastin, NADH, and flavins. It was possible to generate support for the medical diagnosis of precancerous lesions on cervix tissue by applying the model with developed algorithms. A good fit of the spectrum was obtained and predictions to the model were properly made, with significative differences for each fluorophore parameter, especially on collagen and NADH.

Implementation of ANFIS +NN and nature-inspired optimization algorithms for solar radiation prediction

Edgar Dario Obando Paredes — 2025-07-23

This article presents a hybrid model that uses ANFIS (adaptive neuro-fuzzy inference system) hybridized with neural networks (NN) and optimized with algorithms based on natural behaviors, specifically ant colony optimization (ACO). The model is designed to predict primary resources in a specific region targeted for the planning and installation of distributed photovoltaic (PV) generation. The solar primary resource depends on the climatic conditions of the region to be evaluated, and its high variability over short periods presents a challenge in planning energy resources that rely on variable sources in the long term. In this study, the behavior of a hybrid ANFIS + NN + ACO model is designed, developed, evaluated, and validated. The methodology, based on data analysis, is detailed. First, work is carried out on climatic databases, which provide guidelines for preprocessing and cleaning. Second, the climatic variables used to predict solar radiation are identified. ANFIS membership functions are then based on the data to capture nonlinearity and extract relationships with predictors. Neural networks support the optimization of the membership functions, and finally, the optimizer refines and evaluates the response. The response is evaluated using metrics that demonstrate the robustness of the model in capturing and processing data. This study contributes by highlighting tools and alternatives to determine energy potential in climatic regions subject to future distributed generation.

Model of an ideal Rankine cycle with reheating in E.E.S

Diego Alejandro Narváez Meza — 2025-06-30

In the present study, a comprehensive analysis is carried out on an ideal regenerative Rankine cycle, based on the use of ICT tools for digital transformation in engineering education. The gap addressed in this work relates to the application of technologies to streamline the thermodynamic analysis of complex cycles, which have been rigorously modeled using the Engineering Equation Solver (E.E.S.) software a high-fidelity computational tool widely recognized for its accuracy in solving nonlinear, multivariable thermodynamic systems. The methodological approach adopted involves a detailed evaluation of the isentropic efficiencies of the main cycle components turbines, pump, and heat exchangers enabling a precise determination of the net power output, the rates of thermal energy transfer to and from the heat exchangers, as well as the quantification of the mass flow rates of extracted steam at specific points in the system for regenerative purposes. Additionally, the computational generation of temperature–entropy (T–s) diagrams is integrated, which serve as fundamental tools for the visualization and validation of the thermodynamic processes involved, allowing for the clear identification of each state in the cycle. Based on this graphical representation and the numerical results derived from the model, key thermodynamic properties are determined, such as specific volume at pump suction, entropy at turbine inlet, and enthalpies associated with each energy transformation, in order to quantitatively establish the isentropic efficiency of the devices and their influence on the overall efficiency of the regenerative cycle. This approach enables not only a comprehensive understanding of system behavior but also the identification of improvement opportunities for the energy optimization of advanced thermoelectric cycles.

La revisión científica como acto formativo y garante del conocimiento

Jimmy Alexander Cortes Osorio — 2025-06-30

En la de publicación científica, el revisor tiene un lugar esencial y, a la vez, discretamente invisible. Sus funciones son éticas académicas, éticas y formativas. Serlo no significa ejercer un juicio autoritario ni redactar una sentencia, más bien implica una gran responsabilidad con la comunidad académica que ha reconocido sus méritos. Pese a ello, la mayoría de las veces se realiza esta labor sin conciencia plena del impacto que la evaluación puede ejercer sobre una trayectoria investigativa o incluso sobre una línea de trabajo. Mas allá del juicio, un buen par evaluador es un lector objetivo, crítico, cuidadoso y comprometido que se identifica como un conocedor del tema. No basta con identificar errores o emitir recomendaciones generales. Su dictamen debe contribuir con base en criterios técnicos sólidos, a la mejora del manuscrito conservando siempre profundo respeto por los autores y el tema tratado. Por lo anterior, la revisión debe ser útil para el autor y para el editor, actuando como una oportunidad más mejoramiento de un manuscrito en desarrollo con oportunidad de publicación. Como señala el Committee on Publication Ethics (COPE), los revisores deben "valorar los méritos del artículo con objetividad, sin prejuicios personales ni consideraciones de nacionalidad, género, religión o afiliación institucional" [1].