Cesar Pedraza

Dr. Cesar Pedraza

Universidad Nacional de Colombia
orcid

Research Focus & Metrics

Academic Career Length

19Years (2008-Present)

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

Representative Publications

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28 August 2020 in Agriengineering
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Anderson Kavir Osorio DelgadoAnderson Kavir Osorio Delgado
Anderson Kavir Osorio Delgado
ALAndres Esteban Puerto Lara
Andres Esteban Puerto Lara
Cesar PedrazaCesar Pedraza
Cesar Pedraza
DJDavid Jamaica
David Jamaica
LRLeonardo Rodríguez
Leonardo Rodríguez
Weed management is one of the most important aspects of crop productivity; knowing the amount and the locations of weeds has been a problem that experts have faced for several decades. This paper presents three methods for weed estimation based on deep learning image processing in lettuce crops, and we compared them to visual estimations by experts. One method is based on support vector machines (SVM) using histograms of oriented gradients (HOG) as feature descriptor. The second method was based in YOLOV3 (you only look once V3), taking advantage of its robust architecture for object detection, and the third one was based on Mask R-CNN (region based convolutional neural network) in order to get an instance segmentation for each individual. These methods were complemented with a NDVI index (normalized difference vegetation index) as a background subtractor for removing non photosynthetic objects. According to chosen metrics, the machine and deep learning methods had F1-scores of 88%, 94%, and 94% respectively, regarding to crop detection. Subsequently, detected crops were turned into a binary mask and mixed with the NDVI background subtractor in order to detect weed in an indirect way. Once the weed image was obtained, the coverage percentage of weed was calculated by classical image processing methods. Finally, these performances were compared with the estimations of a set from weed experts through a Bland–Altman plot, intraclass correlation coefficients (ICCs) and Dunn’s test to obtain statistical measurements between every estimation (machine-human); we found that these methods improve accuracy on weed coverage estimation and minimize subjectivity in human-estimated data.

29 January 2020 in Sensors
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Journal Article
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Diego TibaduizaDiego Tibaduiza
Diego Tibaduiza
RGRICARDO GOMEZ
RICARDO GOMEZ
Cesar PedrazaCesar Pedraza
Cesar Pedraza
DADavid Agis
David Agis
Francesc PozoFrancesc Pozo
Francesc Pozo
The damage identification process provides relevant information about the current state of a structure under inspection, and it can be approached from two different points of view. The first approach uses data-driven algorithms, which are usually associated with the collection of data using sensors. Data are subsequently processed and analyzed. The second approach uses models to analyze information about the structure. In the latter case, the overall performance of the approach is associated with the accuracy of the model and the information that is used to define it. Although both approaches are widely used, data-driven algorithms are preferred in most cases because they afford the ability to analyze data acquired from sensors and to provide a real-time solution for decision making; however, these approaches involve high-performance processors due to the high computational cost. As a contribution to the researchers working with data-driven algorithms and applications, this work presents a brief review of data-driven algorithms for damage identification in structural health-monitoring applications. This review covers damage detection, localization, classification, extension, and prognosis, as well as the development of smart structures. The literature is systematically reviewed according to the natural steps of a structural health-monitoring system. This review also includes information on the types of sensors used as well as on the development of data-driven algorithms for damage identification.

1 August 2020 in Journal of Traffic and Transportation Engineering (English Edition)
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Journal Article
Open access
Camilo Gutierrez-OsorioCamilo Gutierrez-Osorio
Camilo Gutierrez-Osorio
Cesar PedrazaCesar Pedraza
Cesar Pedraza

20 February 2020 in Sensors
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OUOscar Urbano
Oscar Urbano
APAngel Perles
Angel Perles
Cesar PedrazaCesar Pedraza
Cesar Pedraza
S. Rubio-ArraezS. Rubio-Arraez
S. Rubio-Arraez
MCML Castelló
ML Castelló
RMRicardo Mercado
Ricardo Mercado
This paper presents the design and validation of a traceability system, based on radio frequency identification (RFID) technology and Internet of Things (IoT) services, intended to address the interconnection and cost-implementation problems typical in traceability systems. The RFID layer integrates temperature sensors into RFID tags, to track and trace food conditions during transportation. The IoT paradigm makes it possible to connect multiple systems to the same platform, addressing interconnection problems between different technology providers. The cost-implementation issues are addressed following the Data as a Service (DaaS) billing scheme, where users pay for the data they consume and not the installed equipment, avoiding the big initial investment that these high-tech solutions commonly require. The developed system is validated in two case scenarios, one carried out in controlled laboratory conditions, monitoring chopped pumpkin. Another case, carried out in a real scenario, monitors oranges sent from Valencia, Spain to Cork, Ireland.

10 January 2022 in Information
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NSNestor Eduardo Suat-Rojas
Nestor Eduardo Suat-Rojas
Camilo Gutierrez-OsorioCamilo Gutierrez-Osorio
Camilo Gutierrez-Osorio
Cesar PedrazaCesar Pedraza
Cesar Pedraza
Traffic accident detection is an important strategy governments can use to implement policies intended to reduce accidents. They usually use techniques such as image processing, RFID devices, among others. Social network mining has emerged as a low-cost alternative. However, social networks come with several challenges such as informal language and misspellings. This paper proposes a method to extract traffic accident data from Twitter in Spanish. The method consists of four phases. The first phase establishes the data collection mechanisms. The second consists of vectorially representing the messages and classifying them as accidents or non-accidents. The third phase uses named entity recognition techniques to detect the location. In the fourth phase, locations pass through a geocoder that returns their geographic coordinates. This method was applied to Bogota city and the data on Twitter were compared with the official traffic information source; comparisons showed some influence of Twitter on the commercial and industrial area of the city. The results reveal how effective the information on accidents reported on Twitter can be. It should therefore be considered as a source of information that may complement existing detection methods.

18 October 2021 in Sensors
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Journal Article
Open access
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Jersson X. Leon-MedinaJersson X. Leon-Medina
Jersson X. Leon-Medina
Jaiber CamachoJaiber Camacho
Jaiber Camacho
Camilo Gutierrez-OsorioCamilo Gutierrez-Osorio
Camilo Gutierrez-Osorio
JSJulián Esteban Salomón
Julián Esteban Salomón
BRBernardo Rueda
Bernardo Rueda
Diego TibaduizaDiego Tibaduiza
Diego Tibaduiza
The analysis of data from sensors in structures subjected to extreme conditions such as the ones used in smelting processes is a great decision tool that allows knowing the behavior of the structure under different operational conditions. In this industry, the furnaces and the different elements are fully instrumented, including sensors to measure variables such as temperature, pressure, level, flow, power, electrode positions, among others. From the point of view of engineering and data analytics, this quantity of data presents an opportunity to understand the operation of the system under normal conditions or to explore new ways of operation by using information from models provided by using deep learning approaches. Although some approaches have been developed with application to this industry, it is still an open research area. As a contribution, this paper presents an applied deep learning temperature prediction model for a 75 MW electric arc furnace, which is used for ferronickel production. In general, the methodology proposed considers two steps: first, a data cleaning process to increase the quality of the data, eliminating both redundant information as well as atypical and unusual data, and second, a multivariate time series deep learning model to predict the temperatures in the furnace lining. The developed deep learning model is a sequential one based on GRU (gated recurrent unit) layer plus a dense layer. The GRU + Dense model achieved an average root mean square error (RMSE) of 1.19 °C in the test set of 16 different thermocouples radially distributed on the furnace.