The non-linear relationship between the applied force and strain observed in compression tests of plant tissue reflects the structural complexity of plant materials. This feature distinguishes plant materials from homogenous inorganic materials under compression. To elucidate this behavior, a rheological model of a solid composed of spherical cells surrounded by an elastic cell wall and filled with an incompressible fluid was developed. Compression of the sample resulted in the spatial deformation of the cellular-tissue structure, accompanied by displacement of the fluid occupying intercellular spaces. Simulations were performed for two compression modes (free and constrained) and two cell packing arrangements (cubic and tetrahedral), yielding a non-linear relationship in each case across the entire strain range. The simulation results indicate that the average equivalent stress depends primarily on the compression mode and the cell packing arrangement. The average equivalent stress was nearly twice as high for the tetrahedral lattice as for the cubic lattice. The model sensitivity analysis revealed that the average equivalent stress was inversely proportional to the cell radius and directly proportional to the cell wall thickness, and turgor pressure. The proposed model adequately describes the compression of plant materials, and it demonstrated that the results of compression tests are determined by tissue structure, the parameters of plant cells, and the dimensions of the tested sample.

When grain is stored in a silo, a stream of air should be forced through the grain bed to improve its storability. The purpose of forced ventilation is to air, cool, or dry stored grain. The intensity of these processes is determined by various factors, including airflow velocity distribution inside the silo. In turn, airflow velocity distribution is influenced by the parameters of the supplied air, the parameters of the stored plant material, as well as by the silo's structural characteristics. The aim of this study was to propose a model of airflow velocity distribution in a grain bed depending on the values of the above parameters. A mathematical model was developed, formalized, and implemented in a selected programming environment. For the needs of the model, the volume of a silo filled with grain was divided into a finite number of elements with the use of discretization principles that were strictly formalized by the authors. It was assumed that air would flow away from or towards all neighboring elements, as well as across the walls in perforated silos, unless constrained by boundary conditions. The preliminary validation of the wheat grain model was based on literature data, and it revealed that the air supply method and the perforated area of silo walls significantly affected aeration efficiency. At a temperature of 35 degrees C, the optimal results were achieved for a silo floor with 100 % perforated area and solid walls. At a lower temperature (10 degrees C), grain moisture content also decreased, but the drying process was considerably longer. The model was highly consistent with the reference data, and the errors in the prediction of grain moisture content did not exceed 2 %.

This article describes a method for analyzing and modeling a complex agrotechnological system using the example of an industrial grain drying line. Elements of graph theory were used to develop an effective tool for modeling such a system and to formally validate its structure. The proposed method can be applied to transform a general structural model into a set of relational models, to formally evaluate the resulting models’ functionality, and to comprehensively analyze different variants of the process. The method can be deployed at the stage of designing and operating an industrial grain drying line, and it can also be adapted for use in other areas, such as processing lines in the agri-food industry.

Convective cereal grain drying is an energy-intensive process. Mathematical models are applied to analyze and optimize grain drying processes in different types of dryers and in different stages of drying to improve final grain quality and reduce energy consumption. The aim of the present study was to develop a generalized mathematical model of the grain drying process that accounts for all drying stages, including loading and unloading of unprocessed grain, drying, and cooling of dry grain. The developed mathematical model is a system of algebraic equations, where the calculated coefficients are determined by the thermophysical and diffusive properties of dried grain. The model was validated for batch drying of wheat, canola, and corn grain, as well as continuous flow drying of wheat grain. The results were compared with published findings. The relationships between energy consumption during drying and drying time vs. air temperature at the dryer inlet and air stream volume were determined. Dryer capacity and drying conditions specified by the manufacturers, as well as loading and unloading capacity, were considered during batch drying. Continuous flow drying simulations were conducted in counter-flow, parallel-flow, and cross-flow mode. Simulation results indicate that the proposed models correctly depicted process flow in both batch and continuous flow dryers.

The dairy industry is a unique branch of the food production sector, where various decisions have to be made concerning the type and quantity of the manufactured products and the layout of processing lines. The literature on the subject is relatively limited. Therefore, an attempt was made in this study to support decision making in the dairy industry. The article proposes a general methodology for modeling dairy production systems which are characterized by numerous interdependent and concurrent processing operations. The proposed method relies on the object-oriented modeling technique and graph theory, and it can be used to model the equipment and layout of production lines. The method enables multivariate simulations of the production process involving a specific batch of raw materials. The simulated variants differ in the configuration of the production line and/or the allocation of raw materials (semi-finished products) to different segments of the production line. The tested model was verified and validated, and the average relative error of estimation was 3.27% for butter production and 2.46% for buttermilk production. The proposed method could support decision-making in the process of selecting the production strategy, including the assortment and quantity of the manufactured products, and the configuration of production lines.

In cheese-like products, milk components (in particular fat) are partially or completely replaced with non-dairy substitutes. An attempt was made in this study to determine whether Edam-type cheese can be distinguished from its substitute, where milk fat was replaced with palm oil, based on rheological properties. The rheological properties of Edam cheese and its substitute were analyzed during a 16-week ripening period, based on the results of a stress-relaxation test. The values of the rheological parameters were estimated with the use of the generalized Maxwell model and a non-linear model proposed by the authors, which accounted for the plastic deformation of the analyzed samples. The study revealed that both methods were equally effective in describing the stress relaxation process; therefore, they can be regarded as equivalent. Excluding the initial stage of ripening (which is not important from the consumers’ point of view), the replacement of milk fat with palm oil did not influence the rheological properties of Edam-type cheese and the cheese-like product. In subsequent stages of ripening, no significant differences were found in the rheological properties of both products, which could only be used to evaluate their ripeness.

A sophisticated relationship between strain rate and stress in plant tissues subjected to mechanical loads reflects the structural complexity and properties of biological tissues. The aim of this study was to develop a mathematical model explaining the above relationship. A simplified, non-linear rheological model of a cellular solid characterised by elastic cell walls and the presence of incompressible fluid in cells was developed. In this model, changes in tissue deformation are determined by the elasticity of the cell wall, the ratio of cell wall thickness to cell diameter, the flow resistance coefficient and tissue porosity. Plant materials (discs cut out from fresh sugar beet roots, celery roots and potato tubers) were analysed to verify the model's adequacy. The developed model indicates that in samples with a constant volume during compression, stress in compressed tissue is determined not only by strain and strain rate, but also by the cellular structure and the shape of the sample. Further research is needed to test the model in other types of materials. The model should also be analysed for its sensitivity to cell size and shape, and the morphological structure of biological tissues.

The potential absorption of solar energy in photovoltaic thermal (PVT) hybrid solar collectors at different tilt angles was compared in the present study. The optimal tilt angles were tested in three variants: during 1 day, 1 year and a period of 30 years. Simulations were performed based on actual weather data for 30 years, including average hourly total radiation, insolation and air temperature. The apparent movement of the Sun across the sky, solar radiation properties, and the electrical and thermal efficiency of a PVT collector were also taken into account in the simulation model. The optimal orientation of the absorber surface was determined by solving an optimization task. The results of the study indicate that in the long-term perspective, the collector’s performance is maximized when the absorber is positioned toward the south at an elevation angle of 34.1°.

The most popular mathematical models for analyzing the rheological properties of liquid, semi-solid and solid foods were presented. Mechanical tests play an important role in empirical evaluations of the rheological properties of raw materials and food products. Raw materials and food products have liquid, semi-solid and solid consistency. A stress relaxation test is an alternative method for evaluating creep compliance, and it can also provide valuable information about the viscoelastic properties of food. The main emphasis was placed on the rheological models of solid foods. The existing rheological models of solids have several weaknesses, in particular when they are used to describe the results of creep and stress relaxation tests of foods with a cellular structure. The structure of food materials can undergo various changes during processing due to the influence of external factors. Rheological models describing the free flow of liquid and semi-solid foods cannot be used to determine the viscoelastic properties of solid foods and liquids.

Professor Stanisław Pabis passed away suddenly on September 13, 2019, at the age of 94. We lost an outstanding scientist in the field of Biosystems Engineering who founded the scientific school of methodology of empirical sciences and who made a significant contribution to the development of systems engineering in agriculture and food processing.

The aim of this study was to determine the compression characteristics of nonhomogeneous plant materials with a complex morphological structure (beetroots, celery roots, and potato tubers), to compare the analyzed samples with the compression characteristics of reference materials (homogeneous isotropic structural materials: steel coil spring and vulcanized rubber), and to determine the influence of the compression rate on stress in compressed samples. Structural materials and plant materials clearly differed in compression characteristics. Excluding the short initial compression phase, the compression curves for the steel coil spring and vulcanized rubber were straight parallel lines, and the higher the crosshead speed, the higher the lines' location in the diagram. In tests conducted on plant materials, the rate of changes in compression force increased throughout the experiment with an increase in crosshead speed. The greatest variations in compression force resulting from differences in crosshead speed were observed in potato samples. The apparent retardation times determined in the developed rheological model ranged from 0.079 s for the steel coil spring to 6.863 s for potatoes.

This study compares the potential annual energy absorption of a flat-plate solar collector at different tilt angles in Poland. Optimal tilt angles were tested in three variants: over the course of the year, in fall/winter and in spring/summer. The results were compared with automatically tracked collectors where the active surface is perpendicular to the angle at which solar radiation reaches the collector. The results were simulated based on the meteorological data. A comparison of the energy outputs of solar collectors in optimization variants 1, 2, and 3 indicates that variant 1 produces the highest energy output.

The study was performed to examine whether the chemical composition of processed meats can be identified based on their rheological properties. The analyzed material comprised ten types of pork and poultry cold cuts supplied by renowned manufacturers and available throughout Poland. The rheological properties of cold cuts were derived using a nonlinear rheological model and correlated with the results of proximate chemical analysis. An analysis of processed meats did not show correlations between variations in their rheological properties and proximate chemical composition versus production date. However, the results of proximate chemical and rheological analyses supported the identification of the evaluated products. Both methods produced similar results only when the type of product or raw materials were known. The rheological properties of the analyzed processed meat products supported the identification of their protein, ash and dry matter content, but could not be used to estimate their collagen and fat content with satisfactory precision.PRACTICAL APPLICATIONSThe manuscript presents an attempt to develop a mathematical model describing the rheological properties of the analyzed material, including the elastic modulus, consistency index, flow index and flow limit, which are not dependent on the stress relaxation tests used to establish those values. We also described an approach to the identification of protein, ash and dry matter content of sausages based on rheological data, and correlations between rheological/mechanical measurements and the chemical composition of meat products. The indirect method for identifying the proximate chemical composition of processed meat products based on their rheological properties poses an alternative to laborious and timeconsuming analytical techniques, and it can be used to design a simple measuring device. The proposed methodological approach can have important implications for both industrial practice and research.

The key criteria for the assessment of combine harvester are its capacity, and the quality of obtained grain bulk. The simultaneous minimisation of grain losses and the operation time of combine harvester requires, inter alia, the optimal selection of the construction and operating parameters for the straw walker unit, whereas the phenomenon of grain separation and its determinants depending on these parameters are not yet well understood. Therefore, a mathematical model of the process was developed considering: the rheological properties of a straw layer; the phenomena associated with the dynamic strain of the layer, forced by the motion of straw walkers; and the phenomenon of grain separation from a straw-and-grain mixture. The study included natural and simulation experiments. The effects of the following parameters were analysed: the capacity of the straw walker unit; the phase shift angle of the cranks of the straw walker shafts; the angle of inclination of the straw walker sieve surface; the angular velocity; the initial grain content in the mixture. For each combination of parameters under study, the content of separated grain on selected sections of the lengths of walkers was determined. The simulation results indicate that the quality of separation should not be regarded as a simple consequence of the velocity of straw movement over the surface of walkers. The important factors affecting the quality of separation include the kinematic parameters of walkers, dependent not only on the angular velocity, but also on the phase shift angle and the throw of the crank. (C) 2016 IAgrE. Published by Elsevier Ltd. All rights reserved.

The experiment was performed on a layer of straw whose thickness was equivalent to the load of 4 kg m−2. Every straw sample was subjected to 15 strain cycles. A preliminary analysis of the results revealed that compression and decompression curves resemble the proper rational function, where selected parameters of that function were determined by the direction of strain and the number of strain cycles. Straw was described with the use of a rheological model where it was divided into layers subjected to elastic strain and internal friction proportional to the rate of displacement and deformation. Unknown model parameters were estimated based on an analysis of the equation describing the results of the experiment and the results produced by the model simulating the rheological properties of straw. The elastic modulus was directly proportional to load, and its value decreased in successive strain cycles. Internal friction was determined based on the loss of mechanical energy. In fluid dynamics, internal friction is associated with viscosity, whereas in fibrous materials such as straw, mechanical energy is lost mainly due to sliding friction. The losses were minimized in successive strain cycles.

The idea of the Integrated Safety Management Support System for Warmia and Masuria Region is to create an integrated platform (database) collecting and processing information about the state of safety in the region with simultaneous location of the accidents on the map. This system will be designed to collect, store, process, analyze and manage data, while enabling rapid exchange of information between users. Our main goal is to support the operations of the emergency services, increasing the efficiency of their activities. The Integrated Safety Management Support System for Warmia and Masuria Region will mainly be dedicated to:-emergency, such as: police, fire brigade, ambulance services, water service -to improve the exchange of information between individuals,-crisis management centers, public administration and local government -to facilitate the acquisition of the necessary data and analyses,-the residents of the region, tourists -warning of hazards,-others: customs department, educational institutions, energy companies, technical inspection, etc.

•Our non-linear model describes rheological behavior of meat products.•The model was validated for pork and poultry cold cuts available throughout Poland.•The model adequately describes changes in stress in all phases of the relaxation test.•The proposed model can be used to optimize the cold cut production process.

The effect of relative humidity (RH) of air on the mechanical properties of roasted turkey breast was studied using a rheological model. The raw turkey breast with a moisture content of ca. 75%, protein content of ca. 24% and fat content of ca. 1% was roasted in a convection steam oven at 180C and five RH levels (0, 20, 50, 70 and 90%). The elastic modulus decreased, whereas the flow consistency index and the flow limit increased with an increase in RH from 0 to 70%. Significant differences were observed in elastic modulus between RH levels of 0 and 20% versus 50, 70 and 90%. As regard the flow consistency index and the flow limit, significant differences were observed between 0 versus 50 and 70% RH levels. No significant differences in those values were reported at RH exceeding 50%. The flow consistency index was independent of RH of air level.PRACTICAL APPLICATIONSThe proposed method can be used to determine the effect of treatment parameters on the rheological properties of the analyzed product, and to assess its final quality. The presented mathematical model allows to evaluate the rheological properties of turkey breast meat roasted in a convection steam oven independently of the type of mechanical tests used to determine those values. The obtained results support the selection of roasting parameters (relative humidity) aimed at yielding a product with the desired rheological properties.