Tag Archives: modelling.

846-856 A. Mencarelli, F. Marinello, A. Marini and L. Guerrini
Physical parameters kinetics during the drying process of quarters and halves cut tomatoes
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Physical parameters kinetics during the drying process of quarters and halves cut tomatoes

A. Mencarelli, F. Marinello, A. Marini and L. Guerrini*

University of Padua, Department of Land, Environment, Agriculture and Forestry, Viale dell’Università 16, Legnaro (PD), IT35020, Italy
*Correspondence: lorenzo.guerrini@unipd.it

Abstract:

Tomato drying is a time-consuming industrial process. Moreover, the prolonged use of high temperatures decreases the quality of tomatoes and increases the environmental footprint of the process. In most cases, drying is performed on halved tomatoes. Alternatively, the use of quarter tomatoes could guarantee a drying times reduction without compromising the final product quality. This work aimed at modelling changes in physical characteristics of half and quarter tomatoes. The drying tests were conducted at 50 and 60 °C. The kinetics of weight loss, colour change, and volume reduction were determined. Colour change was monitored through image analysis, while volume reduction using RGB-D reconstructions. Based on the results, an increase in the drying temperature and the use of quartered tomatoes allow a significant reduction in drying times. The loss of water kinetic allowed the determination of critical moisture. Between initial and critical moisture, loss of water occurred at constant rate (zero-order kinetic), while after that the rate decreased exponentially (first-order kinetic). The colour kinetics showed an initial constant rate followed by a linear increase for brown pixels. The variation of red pixels did not have a clear trend. Increasing the temperature there was no significant reduction in colour quality while quarter tomatoes showed a greater loss of redness than halved tomatoes. Furthermore, the temperature increase does not affect the volume reduction of the tomatoes. Increasing the temperature and the use of quartered tomatoes are simple solutions to reduce drying times. However, quartered tomatoes are less visually appreciable than halved tomatoes.

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1813-1822 J. Kuře, M. Linda, R. Chotěborský, B. Černilová and M. Hromasová
DEM modelling of tillage tools in sand and verification of draft forces in the soil box
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DEM modelling of tillage tools in sand and verification of draft forces in the soil box

J. Kuře¹²*, M. Linda¹, R. Chotěborský², B. Černilová¹ and M. Hromasová¹

¹Department of Electrical Engineering and Automation, Faculty of Engineering,
Czech University of Life Sciences Prague, Kamýcká 129, CZ165 21 Prague – Suchdol,
Czech Republic
²Department of Material Science and Manufacturing Technology, Faculty of
Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ165 21
Prague – Suchdol, Czech Republic
*Correspondence: kure@tf.czu.cz

Abstract:

Soil resistance is still being important parameter during tillage. By reducing the soil resistance during processing, greater efficiency and cost reduction can be achieved. With the correct design of the shape of the tillage tools, reduction in the force required for tillage can be achieved. New tool designs must be tested in field conditions to determine the effect. Using DEM (Discrete element method) modelling, individual designs can be compared without the need for field tests. However, the accuracy of the model must first be verified on real tests. The paper deals with the creation of a mathematical model of sand, which is used for testing tillage tools in the soil box. The models are focused on tests of various shapes of wings on tillage tools. Draft forces are compared, and the correctness of the model is verified.

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1188–1194 A. Valge, A. Sukhoparov and E. Papushin
Strategic planning of grass forage production in North-West Russia
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Strategic planning of grass forage production in North-West Russia

A. Valge, A. Sukhoparov and E. Papushin*

Federal Scientific Agroengineering Center VIM, branch in Saint Petersburg, Filtrovskoje Shosse 3, p.o. Tiarlevo, RU196625 Saint Petersburg, Russia
*Correspondence: papushinea@yandex.ru

Abstract:

Energy and nutritional value of harvested forage rely heavily on grass vegetative phase and harvesting time. The study aimed to identify rational forage harvesting options in terms of harvesting time. The data for modelling were taken from the literature based on the results of many years’ research. The mathematical models of variation of grass mass and quality depending on days after emergence were created. The possible options of two-step harvesting of forage grass (cocksfoot, Dactylis glomerata) were considered using mathematical methods of nonlinear programming: (1) obtaining maximum hay mass with maximum feed units from specified area of 400 ha and maximum forage yield at full flowering of 15.0 t ha-1; and (2) identifying the harvesting timing and area to obtain the required amount of hay (2,500 t) with a target nutrient content (1,200 feed units). Problem 1 solution was harvesting 1 scheduled for the 45th day after emergence at full earing on 170 ha; harvesting 2 scheduled for the 69th day after emergence at full flowering on 230 ha. In this case, 2,066.5 t of hay with 947 feed units would be obtained. Problem 2 solution was harvesting 1 scheduled for the 43th day after emergence at middle earing on 250 ha; harvesting 2 scheduled for the 65th day after emergence at early flowering on 156 ha. The created models can be effectively applied for forage harvesting in any grassland area required and in any regions.

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739–748 J. Galins, V. Osadcuks and A. Pecka
Evaluation of passive cooling system in plywood enclosure for agricultural robot prototype
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Evaluation of passive cooling system in plywood enclosure for agricultural robot prototype

J. Galins, V. Osadcuks and A. Pecka

Latvia University of Life Sciences and Technologies, Faculty of Engineering, Institute of Energetics, Jana Cakstes boulevard 5, LV-3001 Jelgava, Latvia
*Correspondence: janis.galins@llu.lv

Abstract:

The use of autonomous robots in agriculture has been increasing rapidly in recent years, but is hampered by the complexity of data recording and processing. The prototyping process involves many changes to the housing design during development. Using laser cutting to make a housing is more convenient, faster and cheaper than milling or casting if only one body needs to be made. To speed up the production of autonomous robot prototypes, the body was made of birch plywood using laser-cut parts. The study analyses the efficiency of passive cooling to make sure that birch wood plywood is suitable for the production of a robotic body for outdoor use in agriculture. Under laboratory conditions, temperature measurements were made inside and outside the housing to determine how the heat released by the electronic components dissipates into the environment. An exponential model with a static coefficient and a time constant can be used to determine the recommended operating time at different ambient temperatures when the allowable operating temperature of the component is known. Air flow and heat transfer simulations were performed to represent heat dissipation. Birch plywood can be used for the production of prototype enclosures for agricultural robots, but the design must provide technological solutions for heat dissipation to prevent overheating of electronic components.

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1498-1516 V. Bulgakov, V. Adamchuk, M. Arak, I. Petrychenko and J. Olt
Theoretical research into the motion of combined fertilising and sowing tractor-implement unit
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Theoretical research into the motion of combined fertilising and sowing tractor-implement unit

V. Bulgakov¹, V. Adamchuk², M. Arak³, I. Petrychenko² and J. Olt³*

¹National University of Life and Environmental Sciences of Ukraine, 15 Heroyiv Oborony Str., UA03041 Kyiv, Ukraine
²National Scientific Centre, Institute for Agricultural Engineering and Electrification, 11 Vokzalna Str., Glevaкha-1, Vasylkiv District, UA08631 Kiev Region, Ukraine
³Estonian University of Life Sciences, Institute of Technology, 56 Kreutzwaldi Str., EE51014 Tartu, Estonia
*Correspondence: jyri.olt@emu.ee

Abstract:

A mathematical model has been developed representing the motion of a seed drill combination simultaneously performing the preceding banded placement of mineral fertilisers. Such a combined unit comprises the gang-up wheeled tractor, the fertiliser distribution module behind the tractor attached to it with the use of a hitch and intended for the banded placement of mineral fertilisers and the grain drill behind the fertiliser distribution module attached to it also with the use of a hitch. For the components of this dynamic system the coordinates of their centres, their masses as well as the external forces and the reactions of the soil surface applied to them have been determined. In order to use the original dynamic equations in the form of the Lagrange equations of the second kind, the generalised coordinates and kinetic energy relations have been determined. Following the necessary transformations, a system of six differential equations of motion has been generated, which characterises the behaviour of the combined machine unit during its plane-parallel motion. In this system, two line coordinates and one angular coordinate characterise the behaviour of the propulsion and power unit (wheeled tractor), while three angular coordinates characterise the rotations of the draft gear and the centres of the machines integrated with its use.

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1822–1830 A. Aboltins, J. Priekulis, B. Aboltina and L. Melece
Effect of slurry lagoon redesign on reduction of ammonia emission during livestock manure storage
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Effect of slurry lagoon redesign on reduction of ammonia emission during livestock manure storage

A. Aboltins¹*, J. Priekulis¹, B. Aboltina² and L. Melece³

¹Latvia University of Agriculture, Institute of Agriculture Machinery, Cakstes blvd. 5, LV-3001 Jelgava, Latvia
²Latvia University, Faculty of Physics and Mathematics, Zellu str. 25, LV-1002 Riga, Latvia
³Institute of Agricultural Resources and Economics, Struktoru str. 14, LV-1039 Riga, Latvia
*Correspondence: aivars.aboltins@llu.lv

Abstract:

In accordance with the international and EU aims to reduce emissions of ammonia and other air pollution substances farm manure management, including its storage, especially for the animal breeding sector, is one of the most essential stages. One of the preventing steps is covering of the slurry lagoons. The most effective – hard covering can be provided only after the lagoon is constructed. The aim of the research: to develop methodology for calculations of emission reducing lagoon design volume and surface area. In the result of the theoretical research the possibilities of reducing the reflection surfaces at the same capacity of the lagoon have been discovered, as well as the changes of the reflection surface area, if instead of one lagoon several lagoons with less volume are installed and sequential filling of these lagoons is ensured. The article presents the calculation algorithms obtained during the research and recommendations for construction of low emission lagoons.

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1232–1240 Z. Vondrášek
Numerical Modelling of Transient Phenomena in a Synchronous Machine
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Numerical Modelling of Transient Phenomena in a Synchronous Machine

Z. Vondrášek

1Czech University of Life Sciences Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamýcká 129, CZ 16521 Praha 6 – Suchdol, Czech Republic; e-mail: vondrasek@tf. czu.cz

Abstract:

The present contribution deals with the idea of identification of electromagnetic transient phenomena pages in a synchronous machine – namely of distant short circuits – by numerical modelling. Phenomena in AC windings of a synchronous machine (stator) have a backswing effect on the phenomena in DC windings – namely the excitation one. Concerned is namely the current stress of the excitation circuit during the transient phenomenon. The computer model is created in the Famulus- vers. 3 – environment. The time behaviour of AC circuit currents in components d, q and the excitation circuit is monitored on the example of a 3-pole distant short circuit in a synchronous machine (via the impedances of connecting elements). The results are compared of models with a simpler structure (one damper circuit in the rotor) with those with a more complicated structure (two damper circuits in the rotor). 

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689–710 V. Bulgakov, V. Adamchuk, M. Arak, V. Nadykto, V. Kyurchev and J. Olt
Theory of vertical oscillations and dynamic stability of combined tractor-implement unit
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Theory of vertical oscillations and dynamic stability of combined tractor-implement unit

V. Bulgakov¹, V. Adamchuk², M. Arak³, V. Nadykto⁴, V. Kyurchev⁴ and J. Olt³*

¹National University of Life and Environmental Sciences of Ukraine, 15, Heroyiv Oborony Str., UK 03041 Kyiv, Ukraine
²National Scientific Centre, Institute for Agricultural Engineering and Electrification, 11, Vokzalna Str., Glevaкha-1, Vasylkiv District, UK 08631 Kiev Region, Ukraine
³Estonian University of Life Sciences, Kreutzwaldi 56, EE51014 Tartu, Estonia
⁴Tavria State Agrotechnological University of Ukraine, Khmelnytskoho pr. 18, Melitopol, UK 72312 Zaporozhye region, Ukraine
*Correspondence: jyri.olt@emu.ee

Abstract:

 Currently, throughout the world quite extensive use is made of combined tractor-implement units, which are capable of performing several process operations in the same pass. At the same time, the state-of-the-art ploughing and general-purpose tractors that can carry as front- so rear-mounted implements and accordingly feature both the front and rear PTOs, also able to travel efficiently as forward so in reverse gear, are most suited for the performance of such operations. Authors developed and successfully tested a combined tractor-implement unit on the basis of a wheeled ploughing and general-purpose tractor, which can in one pass efficiently chop the after harvesting crop residues with a front-mounted rotary chopper and simultaneously perform tillage with a rear-mounted plough. The aim of this study is the elaboration of the theoretical basis for the process of vertical oscillation of the combined ploughing and chopping tractor-implement unit and the validation of its dynamic stability in the longitudinal and vertical plane. The research has been performed with the use of the methods of designing the analytical mathematical models of functioning of agricultural machines and machine assembly units based on the theory of tractor, the vibration theory, the theory of automatic control and dynamic stability and the methods of computer programme construction and PC-assisted numerical computation. The dynamics of the said unit have been studied basing on the analysis of the amplitude frequency characteristics of the unit as a dynamic system responding to external perturbations appearing in the form of soil surface irregularities. Following the results of the undertaken analytical study, first the equivalent schematic model of the discussed combined tractor-implement unit in the longitudinal and vertical plane was developed, the unit’s characteristic points were defined, the linear and angular displacements specified and acting forces applied. Each pneumatic-tyre wheel of the unit represented by its elastically damping model had point contacts with the soil surface irregularities defined by the respective elevations. Using the original dynamic equations in the form of the Lagrange equations of the second kind, first we defined the generalised coordinates and the formulae for the kinetic and potential energy, dissipation functions and generalised forces, then, after performing the necessary transformations, we set up the system of four differential equations, which described the motion of the dynamic system under consideration. Further, we applied the Laplace transformations to the obtained differential equation system, which provided for obtaining the system of equations in the operator form and preparing them for the representation suitable for PC-assisted numerical calculations with the use of the developed computer programme. In accordance with the numerical computation results, graphs were plotted for the amplitude and phase frequency response characteristics of the tractor’s vertical oscillations at different stiffness coefficients of its steering wheels, the amplitude frequency response characteristics of the chopper’s oscillations depending on its mass and its support wheel tyres’ stiffness coefficient as well as the characteristics of the plough’s oscillations at different stiffness coefficients of its pneumatic-tyre ground support wheel.

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556–568 J. Prchalová, H. Čížková, R. Ševčík, K. Hanušová and A. Rajchl
Evaluation of shelf-life of fruit baby food
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Evaluation of shelf-life of fruit baby food

J. Prchalová, H. Čížková, R. Ševčík, K. Hanušová and A. Rajchl*

Department of Food Preservation, University of Chemistry and Technology Prague,
Technická 5, CZ 160 28 Prague 6, Czech Republic
*Correspondence: ales.rajchl@vscht.cz

Abstract:

Fruit baby food is an important food source in infant nutrition. This ambient stable product is processed using heat treatment and can be stored for one or more years at ambient temperature. An accelerated shelf-life storage test of fruit baby food was carried out. Sets of samples were stored at various storage temperatures (40, 55, 70 and 90 °C) for 3 weeks. Selected markers were followed and correlated with sensory evaluation during the storage. The markers were: DPPH, total phenols, ascorbic acid, 5-HMF, furfural and colour (expressed as L, a*, b* and nE). Kinetic data (reaction rate constants, activation energies, Q10, z values) were calculated. The aim of the paper was to evaluate shelf-lives of fruit baby food. The colour parameters, especially nE, seem to be a robust criterion which could be used to predict shelf-lives of fruit baby food.

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1165-1192 V. Bulgakov, V. Adamchuk, M. Arak and J. Olt
Theory of vibration-assisted sugar beet root lifting
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Theory of vibration-assisted sugar beet root lifting

V. Bulgakov¹, V. Adamchuk², M. Arak³ and J. Olt³⋅*

¹National University of Life and Environmental Sciences of Ukraine 15, Heroyiv Oborony Str., UK03041 Kyiv, Ukraine
²National Scientific Centre, Institute for Agricultural Engineering and Electrification, 11, Vokzalna Str., Glevaкha-1, Vasylkiv District, Kiev Region, UK08631, Ukraine
³Estonian University of Life Sciences, Institute of Technology, 56 Kreutzwaldi Str., EE51014 Tartu, Estonia;
*Correspondence: jyri.olt@emu.ee

Abstract:

The vibration-assisted lifting of sugar beet roots from the soil has been gaining increasingly wide use worldwide and the majority of sugar beet harvesting machinery manufacturers produce beet harvesters equipped with just such kind of lifting units. In such units the priorities are low tractive resistance, the high quality of harvesting in terms of undamaged side surfaces of beet root bodies and intact tail parts as well as the high degree of their initial cleaning from the stuck soil. However, the parameters of the oscillatory processes generated by the vibrational lifting units used on the majority of sugar beet harvesting machinery in the market have rather average values appropriate for relatively favourable harvesting conditions (soft loose soil, beet root sizes close to the average, properly lined up planting rows etc.). But when the harvesting conditions deviate from their favourable values (especially in case of dry and strong soil), the vibrating lifters start performing the digging process with significant damage to the beet roots (breaking and tearing off the tail parts), their power consumption rises excessively sharply, the unit vibration drives prove to be unreliable. The literature source analysis has shown that any sufficiently detailed, comprehensive and dependable theory of direct beet root lifting from the soil is virtually absent. Thus, the aim of this research study has been to work out such a theoretical basis for the process of vibration-assisted beet root lifting, which will allow to calculate, in accordance with the harvesting parameters, the optimal design and kinematic parameters of the process ensuring the high quality of harvesting. A new theory has been developed, which describes the process of direct vibration-assisted beet root lifting performed under the effect of the vertical disturbing force and the pulling force, imparted to the root by the lifting unit. The obtained system of differential equations has made it possible to establish the law of motion of the beet root in the process of its direct vibration-assisted lifting and perform PC-based numerical calculations, which provide the basis for determining optimal kinematic modes of operation and design parameters of vibrational lifting units subject to the condition of maintaining sugar beet roots intact when harvesting them.

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