Yahya ZEFRI

Mr. Yahya ZEFRI

orcid

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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23 November 2018 in Drones
Verified
Journal Article
Open access
PDF file
YZYahya ZEFRI
Yahya ZEFRI
AEAchraf ElKettani
Achraf ElKettani
ISImane Sebari
Imane Sebari
SASARA AIT-LAMALLAM
SARA AIT-LAMALLAM
Being sustainable, clean, and eco-friendly, photovoltaic technology is considered as one of the most hoped solutions face to worldwide energetic challenges. Morocco joins this context with the inauguration of numerous clean energy projects. However, one key factor in making photovoltaic installations a profitable investment are regular and effective inspections in order to detect occurred defects. Unmanned aerial vehicles (UAV) are increasingly used in various inspection fields. In this respect, this work focuses on the use of thermal and visual imagery taken by UAV in the inspection of photovoltaic installations. Visual and thermal images of photovoltaic modules, obtained by UAV, from different installations, and with different acquisition conditions and parameters, were exploited to generate orthomosaics for inspection purposes. The methodology was tested on a dataset we have acquired by a mission in Rabat (Morocco), and also on external datasets acquired in Switzerland. As final results, several visual defects were detected in visual RGB and thermal orthomosaics, such as cracks, soiling, and hotspots. In addition, a procedure of semi-automatic hotspots’ extraction was also developed and is presented within this work. On the other side, various tests were conducted on the influence of some acquisition and processing parameters (images’ overlap, the ground sampling distance, the flying height, the use of ground control points, the internal camera parameters’ optimization) on the detection of defects and the quality of visual and thermal generated orthomosaics. In the end, the potential of UAV thermal and visual imagery in the inspection of photovoltaic installations was discussed in function of various parameters. On the basis of the discussion feedback, UAV were concluded as advantageous tools within the thematic of this project, which proves the necessity of their implementation in this context.

23 March 2023 in Expert Systems with Applications
Verified
Journal Article
Closed access
YZYahya ZEFRI
Yahya ZEFRI
ISImane Sebari
Imane Sebari
HHHicham Hajji
Hicham Hajji
GAGhassane Aniba
Ghassane Aniba
Mohammadreza AghaeiMohammadreza Aghaei
Mohammadreza Aghaei

1 August 2021 in Remote Sensing Applications: Society and Environment
Verified
Journal Article
Closed access
YZYahya ZEFRI
Yahya ZEFRI
ISImane Sebari
Imane Sebari
HHHicham Hajji
Hicham Hajji
GAGhassane Aniba
Ghassane Aniba

1 December 2017
Verified
Conference Paper
Closed access
YZYahya ZEFRI
Yahya ZEFRI
AEAchraf Elkcttani
Achraf Elkcttani
ISImane Sebari
Imane Sebari
SASARA AIT-LAMALLAM
SARA AIT-LAMALLAM
Unmanned aerial vehicles (UAV) are increasingly used in various inspection fields. In this context, the present work focuses on the use of thermal infrared and visual imagery acquired by UAV in the inspection of photovoltaic installations. In the experiment presented within this work, visual and thermal images of photovoltaic modules, obtained by UAV were exploited to generate orthomosaics in the aim of inspecting targeted installations. The methodology was tested on a dataset we have acquired from a mission on Rabat (Morocco). As results, several visual defects were found in visual RGB orthophotos such as cracks and soiling, whereas thermal ones didn't reveal any abnormal profile temperatures. A methodology of hotspots' automatic extraction is also presented and tested on a dataset acquired on Switzerland. In the end, the potential of UAV thermal and visual imagery in the inspection of photovoitaic installations is discussed in different contexts. On the basis of the discussion feedback, UAV were concluded as advantageous tools within the thematic of this project, which proves the necessity of their implementation in the Moroccan context.

14 May 2024 in Land
Verified
Journal Article
Open access
PDF file
SFSanaa Fadil
Sanaa Fadil
ISImane Sebari
Imane Sebari
MAMoulay Mohamed Ajerame
Moulay Mohamed Ajerame
RARayhana Ajeddour
Rayhana Ajeddour
IMIbtihal El Maghraoui
Ibtihal El Maghraoui
MJMouad Jabrane
Mouad Jabrane
Spatialization of biomass and carbon stocks is essential for a good understanding of the forest stand and its characteristics, especially in degraded Mediterranean cork oak forests. Furthermore, the analysis of biomass and carbon stock changes and dynamics is essential for understanding the carbon cycle, in particular carbon emissions and stocks, in order to make projections, especially in the context of climate change. In this research, we use a multidimensional framework integrating forest survey data, LiDAR UAV data, and extracted vegetation indices from Landsat imagery (NDVI, ARVI, CIG, etc.) to model and spatialize cork oak biomass and carbon stocks on a large scale. For this purpose, we explore the use of univariate and multivariate regression modeling and examine several types of regression, namely, multiple linear regression, stepwise linear regression, random forest regression, simple linear regression, logarithmic regression, and quadratic and cubic regression. The results show that for multivariate regression, stepwise regression gives good results, with R2 equal to 80% and 65% and RMSE equal to 2.59 and 1.52 Mg/ha for biomass and carbon stock, respectively. Random forest regression, chosen as the ML algorithm, gives acceptable results, explaining 80% and 60% of the variation in biomass and carbon stock, respectively, and an RMSE of 2.74 and 1.72 Mg/ha for biomass and carbon stock, respectively. For the univariate regression, the simple linear regression is chosen because it gives satisfactory results, close to those of the quadratic and cubic regressions, but with a simpler equation. The vegetation index chosen is ARVI, which shows good performance indices, close to those of the NDVI and CIG. The assessment of biomass and carbon stock changes in the study area over 35 years (1985–2020) showed a slight increase of less than 10 Mg/ha and a decrease in biomass and carbon stock over a large area.