•Implementation of novel three-point-hitch measuring system.•Investigation of potential of new measuring system for better soil observation.•Utilization of geostatistics for maps generation of soil ...physical properties.•Study of interactions between soil tillage resistance and standard soil properties.
Horizontal and vertical variability of soil properties, temporal dynamics, and the complexity of monitoring and prediction processes are the limiting factors for full implementation of all the postulates of site specific crop management. The aim of this research was to prove the possibilities for utilization of original soil tillage resistance measuring device in spatial assessment of some physical properties of soil.
The tillage resistance measurement and soil evaluation were performed in 2012 on a field of 0.78ha, with calcic chernozem type of soil. The year before, the field was divided into three equal plots where three types of tillage were applied (moldboard plowing, disc harrowing and chisel plowing) in order to increase spatial soil differences and to ensure more reliable testing. Soil physical properties were observed at 30 points that were arranged on the nodes of a rectangular grid all over the field along with their geopositioning. Soil tillage resistance was measured in real time and space, during 30 passes that were made on the entire field by a standard tractor and plow.
The tillage management applied in 2011 resulted in the differences of some soil parameters. Significant differences between the field plots arose with respect to cone index, moisture content and soil tillage resistance. However, no differences arose regarding the texture (sand, silt+clay content) and bulk density. The correlation analysis showed a high positive correlation between soil resistance and cone index (R=0.82) and a negative correlation between soil resistance and moisture content (R=−0.41). Fitting of variograms in the modeling of spatial correlation gave the highest prediction error for cone index (13.9%), then for tillage resistance (9.32%), sand content (3.95%), moisture content (3.34%), bulk density (2.4%), and finally clay+silt content (2.2%). The generated maps showed that the soil compaction, moisture and tillage resistance had certain orientations with respect to the field plots.
Rapid growth in the energy consumption has conditioned the need for discovering the alternative energy resources which would be adapted to the existing engine constructions and which would satisfy ...the additional criteria related to the renewability, ecology and reliability of use. Introduction of biodiesel has been the focus of attention over the last ten years. The aim of this research is to investigate the influence of biodiesel on the performances and exhaust gas emissions of medium power agricultural tractor engines (37-66 kW). The reason for the selection of this category is that those types of tractors are most frequently used in agriculture. In this research biodiesel produced from sunflower oil was blended with fossil diesel. Biodiesel, fossil diesel and fossil diesel blends with 15, 25, 50 and 75%v/v biodiesel were tested for their influence on the engine performances and emissions. The testing was performed on a four-cylinder diesel engine with 48 kW rated power. The experimental research on the engine performances was conducted in compliance with OECD test CODE 2, and the exhaust gas emissions were tested according to the ISO 8178-4, C1. The use of biodiesel and fossil diesel blends reduced the engine power with the increase of biodiesel share in the blend. However, the exception was the blend with 15%v/v biodiesel which induced a slight increase in the engine power. Depending on the share of biodiesel in the blend all blends fuels showed increased specific fuel consumption compared to the fossil diesel. Thermal efficiency increased as a result of more complete combustion of biodiesel and fossil diesel blends. The exhaust gas emissions implied that the addition of biodiesel reduced the content of CO2 and CO, as well as the temperature of exhaust gases, but it increased the emission of NOx.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study reviews test results for a biomass-fired hot water boiler with a nominal boiler thermal power of 120 kW. In the experiments, prismatic wheat straw bales were used as biomass. The impact of ...the quantity (220, 290, 360 and 430 m3 h−1) of inlet air fed to the boiler firebox was continuously monitored. This was to examine the influence of the quantity of inlet air and recirculation (0, 16.5 and 33%) of combustion products on the boiler thermal power and boiler energy efficiency. Thus, the following mathematical models and formulas were presented: correlation between boiler thermal power and bale residence time; bale mass loss during the combustion process; correlation between boiler energy efficiency and bale residence time. Mathematical models were obtained by using experimental data and by applying nonlinear regression analysis. Adjustment evaluation of mathematical models with experimental data was performed based on the determination coefficient, t-test and F-test. Increase the amount of air throughout the firebox produced boiler thermal power increase and bale residence time decrease. It was shown that combustion products recirculation of 16.5% partly improved boiler characteristics, while the recirculation of 33% did not, comparing with the case without recirculation.
Harsh requirements regarding the exhaust gases emission have conditioned the development of new systems in the engine, as well as the development of ecological fuels. Sulfur extraction considerably ...impairs the lubrication properties of diesel fuel. This has consequences in the rapid wear of the elements that constitute the fuel injection system. Additives for the improvement of lubrication properties are added with the aim of eliminating the adverse effect of fuel. The problem related to the use of those additives lies in the fact that they contain heavy aromatic solvents such as methyl naphthalene, methyl naphthalene and biphenyl which are harmful to health. Therefore, the aim of this research is to determine whether there is a possibility to use biodiesel for the improvement of lubrication properties of fossil diesel with low sulfur content instead of standard additives.
Due to Koelreuteria paniculata Laxm., high abundance in Novi Sad (Serbia) and previously confirmed biodiesel feedstock suitability, this study aimed to assess generative potential and yield, assess ...K. paniculata invasive risk, and investigate the influence of harvesting periods on the oil content and quality. Fifty-five specimens present in the Novi Sad inner-city core exhibited very high scores in the conducted invasiveness risk assessment (score 35/39). Determined good overall adaptability, growth and development, vitality and decorativeness of K. paniculata specimens, as well as the absence of phytopathological and entomological damages, due to lack of natural enemies, provided this species high unhindered yielding. The majority of investigated trees reached 5–10 m in height and canopy volumes from 10.1 to 70 m3, with an estimated more than 130 000–700 000 seeds produced per canopy. Seeds from one representative specimen were collected on different harvesting dates, at the end of August, September and October of 2019, and analyzed for oil content and quality for biodiesel production. With the average oil percentage of 22.8 w%, determined in the representative specimen, investigated 55 seed-bearing K. paniculata trees merely in the inner city core of Novi Sad, could produce 115 kg of oil. Since oil properties (<1 w% of free fatty acids and the acid number <2 mgKOH.g−1) and fatty acid profile (high content of monounsaturated fatty acids ≈72 w%) fit the requirements set in EN14214 biodiesel standard, regardless of the harvest date, harvest season can be extended to at least three months without compromising the oil quality for biodiesel production. Thus, intrinsic disservice of K. paniculata – high seed yielding can be shifted into a novel ecosystem service – quality biodiesel production. Aiming to avoid viable seed deposition in the ground and formation of the invasive seed bank, early August harvest can be recommended.
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•Koelreuteria paniculata showed high invasiveness risk in the city of Novi Sad.•K. paniculata had good overall adaptability and high yielding capacity.•Oil quality fit the requirements of EN14214 standard, regardless of the harvest date.•K. paniculata harvest can last at least 3 months without compromising the oil quality.
•Power delivery efficiency (PDE) of tractor was calculated based on the wheel slippage.•Wheel slippage was expressed as a function of the drawbar force and its angle.•Mathematical equations and an ...algorithm were formed for the calculation of PDE.•It was examined the influence of oblique drawbar force at two soil surfaces on PDE.•The importance of properly attaching the implement to the tractor was confirmed.
The offset position of an implement creates an oblique drawbar force. This force occurs when the resistance direction of the implement is at a certain angle with respect to the longitudinal axis of the tractor (tractor traction direction). The focus of this study was to demonstrate the dependence of wheeled tractor power delivery efficiency on wheel slippage for central and oblique drawbar forces, both on plowed and unplowed stubble. For this purpose, the travel speed of tractor, wheel slippage, drawbar force and engine speed were measured. Mathematical models were formed using a nonlinear regression analysis, and after that, an algorithm for calculating the power delivery efficiency of wheeled tractors depending on the drawbar force and the angle of the drawbar force was developed. This method allowed us to determine the dependence of the power delivery efficiency on the wheel slippage for different angles of the drawbar force. The highest power delivery efficiency of a tractor is achieved at a central drawbar force (angle of the oblique drawbar force equals zero). Results showed the influence of oblique drawbar force on the power delivery efficiency of the wheeled tractor on soft and loose types of soil. Power delivery efficiency of the tractor on unplowed stubble decreased by 6.7% when the angle of the oblique drawbar force increased to 10 degrees, and by 15.0% when the angle of the oblique drawbar force increased to 20 degrees. On plowed stubble, power delivery efficiency decreased by 10.4% at a 10 degree angle of oblique drawbar force and by 21.9% at an angle of oblique drawbar force of 20 degrees. The importance of properly attaching the implement to the tractor was also confirmed.
•Theoretical analysis of kinematics of seed fall.•Verification of photo-sensor system reliability in laboratory research for seeding equipment.•Suggestions for improvement of the seeding evaluation ...process.•Application of Design of Experiment method for seeding process optimization.•Assessment of the influence of individual and combined factors affecting quality of seeding distribution.
Contemporary trends have set the need for high precision systems in agricultural operations, but it is the seeding technology in the first place that must satisfy the toughest demands to achieve the highest possible profit. The improvement of seeding precision is impossible without knowledge of the working principles of all parts of a singulation mechanism and all factors which influence the seeding errors. The evolution of a seeder depended crucially on the improvement of the testing methodology and techniques. This paper presents a photo-electronic device which monitors the seed flow at free fall after leaving the seeding mechanism. An air blowing seeding mechanism was used to simulate the seeding. Its performances were tested with seven varieties of corn seed, two seeding plates, two different air flow rates, and four different speeds of revolution of the seeding plate. A full factorial design was used to determine the significance of influence of four input factors and interactions of two of them. Data validation was done by comparing the values calculated according to visual analysis of high-speed camera recordings and photo-electronic system data where a strong relationship was achieved (R2 > 0.99). It was determined that the speed of revolution of the seeding plate had the greatest influence on the varying distance between the consecutive seeds, while the seed variety exerted the least influence. The pressure of air flow and the variety of the seeds had the most significant influence on the variation of quality of feed index, although, the type and speed of revolution of the seeding plate were also statistically significant parameters. The occurrence of miss and multiple seed were caused by air flow pressure, variety of the seeds, type of the seeding plate, i.e., speed of revolution of the seeding plate. The applied optimization method can be a useful tool for finding the best possible combination of input parameters observed in the test in order to fulfill the criteria which vary depending on the user’s needs.
Introduction/purpose: Adequate evaluation and choice of off-road vehicles used in performing various types of assignments is a very important factor which affects user mobility and safety as well as ...the quality and efficiency of carrying out transportation activities in the Serbian Armed Forces (SAF). Methods: This paper thus proposes the BWM (Best Worst Method) and the COPRAS (Compressed Proportional Assessment) models for the selection of the optimal off-road vehicle for the needs of the SAF. The relative weight of the criteria used to assess potential off-road vehicles was established using the BWM method. In addition to the COPRAS method which is a component of the basic decision-making model, in this paper, the MABAC (MiltiAttributive Border Approximation Area Comparison) and MAIRCA (MultiAttributive Ideal-Real Comparative Analysis) methods were also applied through result validation. Results: By testing the BWM-COPRAS model on the example of optimal off-road vehicle selection in the SAF, a high rank correlation was achieved. The results were validated through the statistical processing of the results obtained through the implementation of various multi-criteria techniques by applying the Spearman’s rank correlation coefficient. Conclusion: The results display stability of the results of the proposed model in ranking alternatives and prove the feasibility of the proposed approach to handle multi-criteria decision making problems. / Введение/цель: Соответствующее развитие и выбор внедорожных транспортных средств с целью выполнения различных видов задач являются весьма важными факторами, которые влияют на мобильность пользователей, качество передвижения и безопасность при выполнении транспортной деятельности в рамках Вооруженных сил Республики Сербия (ВСРС), а также на эффективность ее осуществления. Методы: В данной работе представлена модель для выбора оптимального внедорожного транспортного средства для нужд ВСРС, с применением BWM (Best Worst Method) и COPRAS (Compressed Proportional Assessment) моделей. Определение относительной сложности критериев на основании, которых производится оценка потенциальных внедорожных транспортных средств выполнено с помощью BWM метода. Наряду с COPRAS методом, который является неотъемлемой частью основной модели принятия решений, в данной работе в части валидации результатов применялись и MABAC (MultiAttributive Border Approximation area Comparison) и MAIRCA (MultiAtributive Ideal-Real Comparative Analysis) методы. Результаты: Испытание BWM-COPRAS модели проведено на примере выбора оптимального внедорожного транспортного средства в ВСС в результате чего был получен высокий коэффициент корреляции рангов. Валидация результатов выполнена с помощью статистической обработки данных, полученных благодаря применению различных многокритериальных методов, в том числе коэффициента корреляций рангов Спирмена. Выводы: Полученные результаты показывают устойчивость результатов предлагаемой модели при ранжировании альтернатив и доказывают ее применимость для решений многокритериальных задач. / Uvod/cilj: Adekvatna evaluacija i izbor terenskog vozila za izvršenje različitih vrsta zadataka veoma je važan faktor koji utiče na mobilnost korisnika, njihovu bezbednost, kao i na kvalitet i efikasnost izvršavanja transportnih aktivnosti u Vojsci Srbije (VS). Metode: Stoga je za izbor optimalnog terenskog vozila za potrebe VS, u ovom radu predložen BWM (Best Worst Method) i COPRAS (Compressed Proportional Assessment) model . Određivanje relativnih težina kriterijuma, na osnovu kojih se vrši vrednovanje potencijalnih terenskih vozila, izvršeno je primenom BWM metode. Pored COPRAS metode, koja je sastavni deo osnovnog modela za donošenje odluke, u ovom radu su, kroz validaciju rezultata, primenjene i metode MABAC (MultiAttributive Border Approximation area Comparison) i MAIRCA (MultiAtributive IdealReal Comparative Analysis). Rezultati: Testiranjem BWM-COPRAS modela na primeru izbora optimalnog terenskog vozila u VS dobijena je visoka korelacija rangova. Validacija rezultata izvršena je statističkom obradom rezultata dobijenih različitim višekriterijumskim tehnikama, primenom Spirmanovog koeficijenta korelacije. Zaključak: Rezultati pokazuju stabilnost rezultata predloženog modela u rangiranju alternativa i dokazuju njegovu primenjivost za rešavanje višekriterijumskih problema.
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