Stavros Kalafatis

Prof. Dr. Stavros Kalafatis

1. Professor of Practice in Electrical and Computer Engineering Texas A&M University Engineering, 3127 TAMU, College Station, TX, USA
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Research Focus & Metrics

Academic Career Length

27Years (2000-Present)

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

Representative Publications

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5 May 2022 in Sensors
Verified
Journal Article
Open access
PDF file
SDSambandh Bhusan Dhal
Sambandh Bhusan Dhal
KJKyle Jungbluth
Kyle Jungbluth
RLRaymond Lin
Raymond Lin
SSSeyed Pouyan Sabahi
Seyed Pouyan Sabahi
MBMuthukumar Bagavathiannan
Muthukumar Bagavathiannan
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
Nutrient regulation in aquaponic environments has been a topic of research for many years. Most studies have focused on appropriate control of nutrients in an aquaponic set-up, but very little research has been conducted on commercial-scale applications. In our model, the input data were sourced on a weekly basis from three commercial aquaponic farms in Southeast Texas over the course of a year. Due to the limited number of data points, dimensionality reduction techniques such as pairwise correlation matrix were used to remove the highly correlated predictors. Feature selection techniques such as the XGBoost classifier and Recursive Feature Elimination with ExtraTreesClassifier were used to rank the features in order of their relative importance. Ammonium and calcium were found to be the top two nutrient predictors, and based on the months in which lettuce was cultivated, the median of these nutrient values from the historical dataset served as the optimal concentration to be maintained in the aquaponic solution to sustain healthy growth of tilapia fish and lettuce plants in a coupled set-up. To accomplish this, Vernier sensors were used to measure the nutrient values and actuator systems were built to dispense the appropriate nutrient into the ecosystem via a closed loop.

1 January 2023 in Sensors
Verified
Journal Article
Open access
PDF file
SDSambandh Bhusan Dhal
Sambandh Bhusan Dhal
SMShikhadri Mahanta
Shikhadri Mahanta
JGJonathan Gumero
Jonathan Gumero
NONick O’sullivan
Nick O’sullivan
MSMorayo Soetan
Morayo Soetan
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
Heavy metal concentrations that must be maintained in aquaponic environments for plant growth have been a source of concern for many decades, as they cannot be completely eliminated in a commercial set-up. Our goal was to create a low-cost real-time smart sensing and actuation system for controlling heavy metal concentrations in aquaponic solutions. Our solution entails sensing the nutrient concentrations in the hydroponic solution, specifically calcium, sulfate, and phosphate, and sending them to a Machine Learning (ML) model hosted on an Android application. The ML algorithm used in this case was a Linear Support Vector Machine (Linear-SVM) trained on top three nutrient predictors chosen after applying a pipeline of Feature Selection methods namely a pairwise correlation matrix, ExtraTreesClassifier and Xgboost classifier on a dataset recorded from three aquaponic farms from South-East Texas. The ML algorithm was then hosted on a cloud platform which would then output the maximum tolerable levels of iron, copper and zinc in real time using the concentration of phosphorus, calcium and sulfur as inputs and would be controlled using an array of dispensing and detecting equipments in a closed loop system.

16 August 2022 in PLOS ONE
Verified
Journal Article
Open access
PDF file
SDSambandh Bhusan Dhal
Sambandh Bhusan Dhal
MBMuthukumar Bagavathiannan
Muthukumar Bagavathiannan
UBUlisses Braga-Neto
Ulisses Braga-Neto
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
With the recent advances in the field of alternate agriculture, there has been an ever-growing demand for aquaponics as a potential substitute for traditional agricultural techniques for improving sustainable food production. However, the lack of data-driven methods and approaches for aquaponic cultivation remains a challenge. The objective of this research is to investigate statistical methods to make inferences using small datasets for nutrient control in aquaponics to optimize yield. In this work, we employed the Density-Based Synthetic Minority Over-sampling TEchnique (DB-SMOTE) to address dataset imbalance, and ExtraTreesClassifer and Recursive Feature Elimination (RFE) to choose the relevant features. Synthetic data generation techniques such as the Monte-Carlo (MC) sampling techniques were used to generate enough data points and different feature engineering techniques were used on the predictors before evaluating the performance of kernel-based classifiers with the goal of controlling nutrients in the aquaponic solution for optimal growth.[27–35]

26 July 2022 in Sensors
Verified
Journal Article
Open access
PDF file
SRSwarnabha Roy
Swarnabha Roy
TVTony Vo
Tony Vo
SHSteven Hernandez
Steven Hernandez
ALAustin Lehrmann
Austin Lehrmann
AAAsad Ali
Asad Ali
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
There is a growing body of literature that recognizes the importance of Multi-Robot coordination and Modular Robotics. This work evaluates the secure coordination of an Unmanned Aerial Vehicle (UAV) via a drone simulation in Unity and an Unmanned Ground Vehicle (UGV) as a rover. Each robot is equipped with sensors to gather information to send to a cloud server where all computations are performed. Each vehicle is registered by blockchain ledger-based network security. In addition to these, relevant information and alerts are displayed on a website for the users. The usage of UAV–UGV cooperation allows for autonomous surveillance due to the high vantage field of view. Furthermore, the usage of cloud computation lowers the cost of microcontrollers by reducing their complexity. Lastly, blockchain technology mitigates the security issues related to adversarial or malicious robotic nodes connecting to the cluster and not agreeing to privacy rules and norms.

17 October 2024 in Scientific Reports
Verified
Journal Article
Open access
PDF file
SDSambandh Bhusan Dhal
Sambandh Bhusan Dhal
SMShikhadri Mahanta
Shikhadri Mahanta
JMJanie Moore
Janie Moore
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
Recent advancements in sustainable agriculture have spurred interest in hydroponics as an alternative to conventional farming methods. However, the lack of data-driven approaches in hydroponic growth presents a significant challenge. This study addresses this gap by varying nitrogen, magnesium, and potassium concentrations in hydroponically grown soybeans and conducting essential nutrient profiling across the growth cycle. Statistical techniques like Linear Interpolation are employed to interpolate nutrient data and a feature selection pipeline consisting of chi-squared testing methods, Linear Regression with Recursive Feature Elimination (RFE) and ExtraTreesClassifier have been used to select important nutrients for predicting water uptake using non-parametric regression methods. For different nutrient growth media, i.e. for soybeans grown in Hoagland + Nitrogen and Hoagland + Magnesium media, the Random Forest regressor outperformed other methods in predicting water uptake, achieving testing Mean Squared Error (MSE) scores of 24.55 (\({\text{R}}^{2}\) score 0.63) and 8.23 (\({\text{R}}^{2}\) score 0.81), respectively. Similarly, for soybeans grown in Hoagland + Potassium media, Support Vector Regression demonstrated superior performance with a testing MSE of 4.37 and \({\text{R}}^{2}\) score of 0.85. SHapley Additive exPlanations (SHAP) values are examined in each case to elucidate the contributions of individual nutrients to water uptake predictions. This research aims to provide data-driven insights to optimize hydroponic practices for sustainable food production.

2 March 2022 in Preprints.org
Verified
Preprint
Open access
PDF file
SDSambandh Bhusan Dhal
Sambandh Bhusan Dhal
KJKyle Jungbluth
Kyle Jungbluth
RLRaymond Lin
Raymond Lin
SSSeyed Pouyan Sabahi
Seyed Pouyan Sabahi
MBMuthukumar Bagavathiannan
Muthukumar Bagavathiannan
Stavros KalafatisStavros Kalafatis
Stavros Kalafatis
Nutrient regulation in aquaponic environments has been the topic of research for many years. Most have focused on appropriate control of nutrients in an aquaponic set-up, but very little research has been done on commercial scale applications. In our model, the input data was sourced on a weekly basis from three commercial aquaponic farms in South-East Texas over the course of a year. Due to limited number of data points, dimensionality reduction techniques like pair-wise correlation matrix was used to remove the highly correlated predictors. Feature selection techniques like the XGBoost classifier and Recursive Feature Elimination with ExtraTreesClassifier were used to rank the features in order of their relative importance. Ammonium and calcium were found to be the top two nutrient predictors and based on the months in which lettuce was cultivated, the median of these nutrient values from the historical dataset served as the optimal concentrations to be maintained in the aquaponic solution. To accomplish this, Vernier sensors were used to measure the nutrient values and actuator systems were built to dispense the appropriate nutrient into the ecosystem via a closed loop.