• Planning and analysis of materials handling processes in production company using modelling and simulations

    pg(s) 121-126

    In this paper is presented the method of planning and analysis of the materials handling line in one production company. The method consists of design, simulations, and analysis with the support of Arena simulation software. The design of the line is accomplished using modular modelling with interconnected modules and blocks, and simulations will be carried out to view the flow of boxes with materials and the functionality of main units and processes. The modelled line contains all the necessary units of the input processes, production and output processes, warehouses, materials handling vehicles, and the process flow of packages. Analysis will investigate key performance parameters and evaluate the functionality of the line. Production and logistics companies are implementing various software to plan and design their materials handling line, internal transports and production processes prior to the implementation and development of their plant. This enables them to plan the work, determine influential parameters and identify problems in the functionality. Results will be given in the graphical and tabular forms, which will represent the analysis of performance parameters and line efficiency.

  • Optimization of Cooling Performance of Horizontal Commercial Refrigerator Prototype with Mathematical Modeling

    pg(s) 118-120

    In recent years, the problem of food safety and traceability has been one of the difficulties faced by restaurant and hotel businesses. Food spoilage can occur at any stage of the food chain; most of all food spoilage is due to improper storage conditions in refrigerators. Increasing attention to food quality and safety requires the development of sensitive and reliable analysis methods as well as innovative technologies for maintaining freshness and food quality. Freshness is a factor that has both health qualities and features that affect customer satisfaction and business profitability. Within the scope of this study, simulation studies were carried out to improve the cooling performance with mathematical modeling on a horizontal commercial refrigerator (operating temperature: -2/+8°C) prototype. Along with the original design, evaluations were made with mathematical modeling according to many different variables (temperature, airflow distribution, etc.) that affect the cooling performance, and R&D gains were achieved in developing the prototype according to the most suitable working conditions.

  • Irrigation Scheduling for Some Crops Under Arid Environment of Rosso, Mauritania

    pg(s) 114-117

    The study was performed to identify irrigation scheduling of some common crops such as seed-maize, tomato, carrot, rice, alfalfa, and tomato plants at arid Rosso province, Mauritania. In that purpose, crop water requirement, ETc, for those crops were calculated by Cropwat software computer program. In results, ETc values for Rice, Alfalfa, Carrot, Maize (grain), and Tomato crops were calculated as about 1378 mm, 1542 mm, 814 mm, 705 mm, and 956 mm respectively. The irrigation water requirements, I, for the examined crops were found as 1677 mm, 1535 mm, 811 mm, 699 mm, and 950 mm, respectively. In accordance with our findings, the following suggestions can be considered; crop pattern should be designated in accordance with current water resources; water delivery systems should be converted to modernized systems; deficit irrigation can be applied for some crops; farmers should be educated about correct water management, and there should be strong relationships between landowners and water managers.

  • A mathematical pathway to achieve sustainable design and friendly management of combined biodiesel/dairy supply chain

    pg(s) 110-113

    This study proposes a mathematical pathway to achieve sustainable design and resource-friendly management of a biodiesel supply chain produced from dairy waste scum. In the work, the features of a combined biodiesel/dairy supply chain are outlined and a set of design and management tools is developed, which is formulated in MILP terms. The optimization criterion is defined in terms of economic sustainability and environmental assessment data is applied as part of it. The purpose of the defined mathematical model is to obtain optimal operating conditions of the considered combined supply chain. A test example based on a case study from Bulgaria was considered. The results of the toolbox implementation can be used as a decision-making tool.

  • Employment of machine learning techniques for crop yield forecasting based on climate parameters

    pg(s) 86-89

    The ability to forecast the annual crop production is of crucial benefit for any country by providing the capability to define their import and export policies, as well as to estimate the economic gain of their agriculture planning. The weather conditions during the year significantly influence the growth of the crop, and the crop yield quantity is highly affected by the climate conditions in the different development cycles of the plant. Recently, the availability of historical climate data benefits the studies in the sector of agricultural sciences and food, and in particular the use of Artificial Intelligence methods in the big data analysis offers a significant opportunity to provide practicable information and actions. The present work aims to develop Machine Learning (ML) model to forecast the wheat yield based on historical climate data in a specific time frame in the Pelagonia valley in North Macedonia, as one of the most important regions for wheat production in the country. After pre-processing and selecting the input features, LS Boost regression model was employed as a ML method for estimation of the wheat yield from climate data, which resulted in high accuracy of wheat yield prediction even with limited dataset, both on the training and on the testing dataset. The research study proved the feasibility of using ML methods to complement the existing models for accurate wheat yield forecasting, providing significant advantage due to the ease of calibrating the ML model parameters.

  • An Engineering Approach to Solve Headbox Slice Opening Control Problem

    pg(s) 84-85

    A headbox of a machine producing a paper sheet has a slice opening controlled in response to signals indicative of total head of fluid in the headbox, the rate of flow of a paper slurry into the headbox and the speed of a inclined wire headbox receiving a jet of slurry emerging from the headbox slice. The slice opening is controlled to affect formation of the paper sheet on the wire. Consistency of the slurry being fed into the headbox is varied to control the position of a dry line on the wire or formation of fibers on the wire. The level of liquid in the headbox is maintained at a predetermined level by a controller. The slice opening is controlled in an anticipatory manner to compensate for the slow response of the total head in the headbox to changes occurring in response to the slurry mass flow rate into and out of the headbox. Since the double flap structure used as the control mechanism is hinged to each other, they move relative to each other, which creates an obstacle in keeping the flap positions constant. Forward kinematic calculations were tried to be made using the angle sensor, but since the sensor resolutions could not respond to small movements due to the size of the flap lengths, the final flap positions were determined by performing inverse kinematic calculations according to the servo motor positions.

  • Modelling of the new route drawing technology for a metal processing efficiency

    pg(s) 82-83

    The results of finite element modeling of a new method with an increased metal processing level were considered. The improvement of the drawing process was achieved by changing the usual scheme of metal movement during deformation, which made it possible to achieve large strains compared to the standard drawing scheme. It is established that step drawing has the advantage of an increased processing level, but it leads to the formation of an inhomogeneous gradient strain.

  • Concept of an energy system emulator

    pg(s) 59-62

    Research, optimization and practical implementation of the optimization processes of energy subsystems of power, heating and industrial plants is a relatively complex task that is unimaginable today without specialized computer support tools. The energy system emulator itself represents a tool for development and application work with energy systems, which is based on today’s standard decentralized control systems. The basic principles of the modular construction of the emulator and an example of its implementation based on the Siemens SIMATIC-S7 DCS system are shown. In addition to the design of the energy systems emulator concept, the article also presents a design of a hydraulic turbine model as the most important subsystem of a hydropower plant, the efficiency calculation of which is analytically demanding and dependent on parameters that are often obtained only by a theoretical estimation. In this article, a fuzzy system was used to create the model based on measured operating data of the turbine flow rate and the height of its water column without any need to know the exact turbine parameters.

  • Experimental and statistical models for determining the critical values of external action parameters on optical elements in extreme conditions of their operation

    pg(s) 55-58

    The study has been carried out and experimental and statistical models have been developed to determine the critical values of external extreme action parameters (intense heat flows, times of their action, increased external pressures) on optical elements made of glass and ceramics, the excess of which leads to their surface destruction (the appearance of cracks, chips and other defects) and, ultimately, to the failure of optoelectronic devices.

  • Optimization of the rubber forming process for the sheet metal part using numerical simulation

    pg(s) 51-54

    This article focuses on the optimization of manufacturability for the aluminium cover produced by rubber forming. Aluminium Al6016 was considered as a material for the cover and its constitutive equations Hill 48 and Hollomon described its properties. The Mooney-Rivlin hyperelastic material model defined material properties for a punch made of rubber. Pam stamp software was used to create the simulation model and evaluation. Results were optimized from the view of thickness reduction and punch stroke when two different rubber hardness were selected.

  • Numerical investigation of wind-assisted ship propulsion systems

    pg(s) 47-50

    The paper studies three of the most applicable wind-assisted ship propulsion systems: soft sails, Dynarig sails and Flettner rotors, in particular the wind forces on the sails. Traditionally, and still most reliably, these forces are determined by model testing in wind tunnels. Unfortunately, experimental results of different WAPS are quite scarce. On the other hand, the intensive development of Computational Fluid Dynamics (CFD) nowadays allows faster and more economical evaluation of aerodynamic forces and optimization of shapes. CFD modelling is applied here for evaluation of the aerodynamic forces on sails.

  • Study of binary liquid capillary bridges stretched between two solid flat surfaces

    pg(s) 13-16

    Liquid capillary bridges (CBs), created between two flat solid surfaces, parallel to each other, are of significant importance for number of scientific and industrial applications. In this paper, we present our experimental investigation of the liquid CBs at stretching, created by two immiscible liquids: cedar oil–water and paraffin-water with common interface. The behaviour of these binary structures was studied and compared with that of the single liquid CBs. It was found that the binary liquid CBs exist in the same definition domain as the single liquid CBs. Moreover, the current paper is focused not only on static, but also on non-equilibrium behaviour of CBs. We demonstrate that the binary liquid CBs can be engineered by the proper combination of polar (water) and non-polar (oil) fluids and these CBs exist within the theoretically predicted domain. The experimental results of water/cedar oil and water/paraffin binary CBs shows that the paraffin spreads in water surface and modifies the overall surface tension of the system, while the cedar oil and water retain their surface properties within the binary structure.