Željko Barač

Prof. Dr. Željko Barač

University of Josip Juraj Strossmayer in Osijek, Faculty of Agrobiotechnical Sciences Osijek
orcid

Research Focus & Metrics

Academic Career Length

11Years (2016-Present)

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

Representative Publications

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27 July 2024 in Agriculture
Verified
Journal Article
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Monika MarkovićMonika Marković
Monika Marković
MKMaja Matoša Kočar
Maja Matoša Kočar
ŽBŽeljko Barač
Željko Barač
ATAlka Turalija
Alka Turalija
Atılgan AtılganAtılgan Atılgan
Atılgan Atılgan
MRMarija Ravlić
Marija Ravlić
Measuring the soil water content (SWC) is a fundamental component of the sustainable management of water resources, soil preservation, and high irrigation efficiency. Non-destructive SWC measurements using soil moisture sensors (SMSs) enables timely irrigation and reduces overirrigation and water stress. Within this context, the performance of four commercial single-point soil moisture sensors (Watermark and tensiometer (Irrometer Company, Inc., Riverside, CA, USA), SM150 (Delta-T Devices, Cambridge, UK)), FieldScout TDR300 (Spectrum Technologies, Aurora, IL, USA) and one soil profile PR2 probe (Delta-T Devices, Cambridge, UK) were tested under anthropogenic eutric cambisol with a silty clay loamy texture (20, 30, and 40 cm) to evaluate accuracy and sensitivity to changes in the SWC in an irrigated apple orchard. The Watermark and tensiometer were additionally tested in the laboratory to convert soil water tension (kPa) to the volumetric soil water content (%vol.). In general, all tested SMSs responded to changes in the SWC, with sensor-to-sensor differences. The Watermark and tensiometer underestimated the SWC, while the TDR overestimated the SWC. The SM150 and PR2 showed high accuracy, i.e., SM150—RMSE-2.24 (20 cm), 2.18 (30 cm) and 2.34 (40 cm), MSE—5.02 (20 cm), 2.93 (30 cm) and 1.89 (40 cm), and PR2—RMSE-1.8 (20 cm), 1.3 (30 cm) and 1.55 (40 cm), MSE-3.23 (20 cm), 1.7 (30 cm) and 2.39 (40 cm) at all observed soil depths.

7 March 2025 in Agriengineering
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Journal Article
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ŽBŽeljko Barač
Željko Barač
MJMislav Jurić
Mislav Jurić
Ivan PlaščakIvan Plaščak
Ivan Plaščak
TJTomislav Jurić
Tomislav Jurić
Monika MarkovićMonika Marković
Monika Marković
This paper presents whole-body vibration prediction in an agricultural tractor based on selected operational parameters using machine learning. Experiments were performed using a Landini Powerfarm 100 model tractor on farmlands and service roads located at the Osijek School of Agriculture and Veterinary Medicine. The methodology adhered to the HRN ISO 5008 protocols for establishing test surfaces, including a smooth 100 m track and a rugged 35 m track. Whole-body vibrational exposure assessments were carried out in alignment with the HRN ISO 2631-1 and HRN ISO 2631-4 guidelines, which outline procedures for evaluating mechanical oscillations in occupational settings. The obtained whole-body vibration data were divided into three datasets (one for each axis) and processed using linear regression as a baseline and compared against three machine learning models (gradient boosting regressor; support vector machine regressor; multi-layer perception). The most accurate machine learning model according to the R2 metric was the gradient boosting regressor for the x-axis (R2: 0.98) and the y-axis (R2: 0.98), and for the z-axis (R2: 0.95), the most accurate machine learning model was the SVM regressor. The application of machine learning methods indicates that machine learning models can be used to predict whole-body vibrations more accurately than linear regression.

10 March 2021 in Applied Sciences
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Monika MarkovićMonika Marković
Monika Marković
GKGoran Krizmanić
Goran Krizmanić
ABAndrija Brkić
Andrija Brkić
Atılgan AtılganAtılgan Atılgan
Atılgan Atılgan
BJBožica Japundžić-Palenkić
Božica Japundžić-Palenkić
ŽBŽeljko Barač
Željko Barač
Watermark, Tensiometer and Time Domain Reflectometry (TDR) are commonly used soil water sensors in irrigation practice whose performance depends on soil type, depth and growing conditions. Here, the results of sensor performance evaluation in different soil depths as well as the field and laboratory testing in silty clay loamy soil are presented. Gravimetric soil moisture samples were taken from sensor installation depths (10, 20, 30 and 45 cm) and used as reference Soil Water Content (SWC). The measurements varied significantly (p < 0.05) across the monitoring depths. On average across the soil depths, there was a strong negative linear relationship between Watermark (r = −0.91) and TDR (r = 0.94), and a moderate negative (r = −0.75) linear relationship between SWC and Tensiometer. In general, Watermark and Tensiometer measured SWC with great accuracy in the range of readily available water, generated larger Mean Difference (MD) than TDR and overestimated SWC, while TDR underestimated SWC. Overall, laboratory testing reduced the root mean square error (RMSE, Watermark = 1.2, Tensiometer = 2.6, TDR = 1.9) and Mean Average Error (MAE, Watermark = 0.9, Tensiometer = 2.04. TDR = 1.04) for all tested sensors.

24 February 2025 in Agriengineering
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ŽBŽeljko Barač
Željko Barač
Ivan PlaščakIvan Plaščak
Ivan Plaščak
TJTomislav Jurić
Tomislav Jurić
Monika MarkovićMonika Marković
Monika Marković
This paper presents research on the impact of vibrations on the hand–arm and body system of agricultural tractor operators as ergonomic indicators in relation to certain operational parameters. The measurements were conducted on a LANDINI POWERFARM 100 tractor on agricultural production areas and access roads of the Agricultural and Veterinary School in Osijek. The measurements followed the ISO 5008:2015 standard, which describes the creation of test tracks: a smooth track of 100 m in length and a rough track of 35 m in length. Body vibration measurements were conducted according to the prescribed standards HRN ISO 2631-1: 1999/A1:2019 and HRN ISO 2631-4:2010. Hand–arm system vibration measurements were performed according to the prescribed standards HRN ISO 5349-1:2008 and HRN ISO 5349-2:2008/A1:2015. After the measured data were processed, a three-factor analysis of variance was performed, where some operational parameters were designated as A—agrotechnical surfaces (6 types), B—tractor speed (6 speeds), and C—tire air pressure (3 pressures), along with multiple regression analysis and the AHP (analytical hierarchical process). This research determined that none of the measured hand–arm system vibrations exceeded the warning (2.5 ms−2) or limit (5 ms−2) values of daily exposure. Furthermore, vibrations affecting the operator’s body in the x-axis at higher speeds and pressures C2 and C3, in the y-axis at higher speeds and pressures C1 and C2, and in the z-axis at the highest speed and pressures C1 and C2 were found to exceed the daily exposure warning value of 0.5 ms−2. It was concluded that the operator’s health is at risk, and it is recommended that the seat’s air suspension system be inspected to prevent further complications in a timely manner.

25 September 2018 in Tehnički glasnik
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DPDavor Petrović
Davor Petrović
ŽBŽeljko Barač
Željko Barač
Mladen JurišićMladen Jurišić
Mladen Jurišić
VTVjekoslav Tadić
Vjekoslav Tadić
IPIvan Plaščak
Ivan Plaščak
The paper presents a review of different sensory systems for trees’ characterization and detection in permanent crops and the detection of plant health status in crop conditions for the purpose of applying the variable application...

1 December 2018 in Tehnicki vjesnik - Technical Gazette
Verified
Journal Article
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ŽBŽeljko Barač
Željko Barač
IPIvan Plaščak
Ivan Plaščak
Mladen JurišićMladen Jurišić
Mladen Jurišić
VTVjekoslav Tadić
Vjekoslav Tadić
DZDomagoj Zimmer
Domagoj Zimmer
VDVinko Duvnjak
Vinko Duvnjak
This paper represents the results of the research of generated noise levels measured in three different years (2010, 2013, and 2015), in accordance with the proscribed norms HRN ISO 6394, HRN ISO 6396 and HRN ISO 5131. The research was...