Freddy Hernández-Barajas

Dr. Freddy Hernández-Barajas

Estadística, Universidad Nacional de Colombia, Medellín, Antioquia, Colombia
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Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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13 October 2023 in Energies
Verified
Journal Article
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CRCatherine Rincón-Maya
Catherine Rincón-Maya
FGFernando Jesus Guevara-Carazas
Fernando Jesus Guevara-Carazas
Freddy Hernández-BarajasFreddy Hernández-Barajas
Freddy Hernández-Barajas
CPCarmen Patino
Carmen Patino
OUOlga Usuga-Manco
Olga Usuga-Manco
In recent years, lithium-ion batteries have gained significant attention due to their crucial role in various applications, such as electric vehicles and renewable energy storage. Accurate prediction of the remaining useful life (RUL) of these batteries is essential for optimizing their performance and ensuring reliable operation. In this paper, we propose a novel methodology for RUL prediction using an individual control chart (ICC) to identify and remove degraded data, a convolutional neural network (CNN) to smooth the noise of sensor data and long short-term memory (LSTM) networks to effectively capture both spatial and temporal dependencies within battery data, enabling accurate RUL estimation. We evaluate our proposed model using a comprehensive dataset, and experimental results demonstrate its superior performance compared to existing methods. Our findings highlight the potential of ICC-CNN-LSTM for RUL prediction in lithium-ion batteries and provide valuable insights for future research.

8 October 2024 in PLOS ONE
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DLDelia Ortega Lenis
Delia Ortega Lenis
DLDavid Arango Londoño
David Arango Londoño
Freddy Hernández-BarajasFreddy Hernández-Barajas
Freddy Hernández-Barajas
PMPaula Moraga
Paula Moraga
Dengue is a vector-borne disease that has increased over the past two decades, becoming a global public health emergency. The transmission of dengue is contingent upon various factors, among which climate variability plays a significant role. However, there remains substantial uncertainty regarding the underlying mechanisms. This study aims to investigate the spatial and temporal patterns of dengue risk and to quantify the associated risk factors in Valle del Cauca, Colombia, from 2001 to 2019. To achieve this, a spatio-temporal Bayesian hierarchical model was developed, integrating delayed and non-linear effects of climate variables, socio-economic factors, along with spatio-temporal random effects to account for unexplained variability. The results indicate that average temperature is positively associated with dengue risk 0-2 months later, showing a 35% increase in the risk. Similarly, high precipitation levels lead to increased risk approximately 2-3 months later, while relative humidity showed a constant risk within a 6 months-lag. These findings could be valuable for local health authorities interested in developing early warning systems to predict future risks in advance.

25 February 2025 in Sensors
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Journal Article
Open access
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CRCatherine Rincón-Maya
Catherine Rincón-Maya
DADaniel Acosta-González
Daniel Acosta-González
FGFernando Jesus Guevara-Carazas
Fernando Jesus Guevara-Carazas
Freddy Hernández-BarajasFreddy Hernández-Barajas
Freddy Hernández-Barajas
CPCarmen Patino
Carmen Patino
OUOlga Usuga-Manco
Olga Usuga-Manco
In the field of sustainable mobility, this study highlights the importance of using machine learning for predictive modeling based on real traffic data collected from instrumented bicycles. The advent of advanced technologies like sustainable mobility apps, sensors, and advanced data analysis methods led to the ability to collect data from various sources, which enabled researchers to estimate battery state of charge (SOC) accurately. Most current research uses them in the lab experiments for data collection. In this work, we use real-time sensors data to construct data-driven models for lithium-ion battery SOC estimation. This research integrates both electric bicycle battery, environmental and route variables to achieve the following goals: (1) Collect a multimodal data set including operational, topography, vehicle, and external variables, (2) Preprocess data obtained from sensors installed on the electric bicycle battery, (3) Create models of lithium-ion battery SOC based on electric bicycle battery and environmental variables, and (4) Assess data-driven models and compare their performance for lithium-ion battery SOC with high accuracy. To achieve that, we conducted a real study to predict the Remaining Useful Life (RUL), as a measure of state of charge, of electric bicycle battery. The study was carried out on a 15 km cycle route in Medellín, Colombia, for 28 days. To estimate the RUL, we used four different machine learning algorithms: Long Short-Term Memory (LSTM), Support Vector Regression (SVR), AdaBoost, and Gradient Boost. Notably, data preprocessing techniques played a pivotal role, with a particular focus on smoothing sensor data using Convolutional Neural Networks (CNN). The results showed a significant improvement in prediction accuracy when using data preprocessing, confirming its importance in improving model performance. Furthermore, the comparison of network performance facilitated the selection of the most effective model for the test data. This study underscores the value of using real-world data to develop and validate predictive models in the pursuit of sustainable mobility solutions, and highlights the critical role of data-driven methodologies in addressing today’s urban transportation challenges.

11 January 2023 in Applied Sciences
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Journal Article
Open access
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DADiana Arango-Botero
Diana Arango-Botero
Freddy Hernández-BarajasFreddy Hernández-Barajas
Freddy Hernández-Barajas
Alejandro Valencia-AriasAlejandro Valencia-Arias
Alejandro Valencia-Arias
Generalized linear mixed models are commonly used in repeated measurement studies and account for the dependence between observations obtained from the same experimental unit. The designs of repeated measurements in which each experimental unit (e.g., subject) is proven in more than one experimental condition are widespread in psychology, neuroscience, medicine, social sciences and agricultural research. Estimation in generalized linear mixed models is often based on the maximum likelihood theory, which assumes that the assumptions about the underlying probability model are correct. These assumptions include the specification of the distribution of random effects. This research study aimed to identify the impact of the incorrect specification of this distribution on the probability of a type I error and the statistical power of the Wald test. This was achieved through a simulation study where different distributions were considered for random effects in generalized linear mixed models with Poisson and negative binomial responses. Evidence of the impact of the incorrect specification was presented in distributions for random effects different from the normal ones. Lognormal was used for random intercepts and bivariate exponential and Tukey for random intercepts and slopes. Lognormal has positive asymmetry and high kurtosis. Exponential has moderate asymmetry and kurtosis, and Tukey has moderate asymmetry and high kurtosis.

19 December 2023 in Journal of Cultural Cognitive Science
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OKOmid Khatin-Zadeh
Omid Khatin-Zadeh
Hassan BanarueeHassan Banaruee
Hassan Banaruee
DFDanyal Farsani
Danyal Farsani
Freddy Hernández-BarajasFreddy Hernández-Barajas
Freddy Hernández-Barajas
MFMirko Farina
Mirko Farina
Fernando Marmolejo-RamosFernando Marmolejo-Ramos
Fernando Marmolejo-Ramos