Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Energy efficiency within green solutions for management of water-energy-food-environment nexus
Get PDFEnergy efficiency is one of the most important research subjects in the process of optimal utilization of energy and water for food production, taking care of the environment. This is the requirement of efficient production and use of green renewable energy within the nexus water-energy-food-environment. Increasing number of inhabitants on the Globe require more energy, water and food. All technologies for energy, water and food production mast respect the criteria of environmental protection. The hydro, solar and wind energy are renewable resources and on the same time they are one of the most sustainable ways of electric energy production. Besides the benefit of clean green energy, the landscape of big solar or wind power plants, or big hydro accumulation and their impact on the environment mast also be the subject for analyses. The aspect of land occupying is a cutting edge research in correlation with the complex goal of using land for food production. This paper presents a green solution for management of the nexus water-energy-food-environment, using renewable resources
The Possibility of Applying a Universal Testing Machine for Evaluating Food Textures
No full textThe evaluation of food texture is an essential aspect of food quality control, directly influencing consumer acceptance and preference. Various methods have been developed to assess food texture, including sensory evaluation, rheological measurements, and instrumental analysis. Among the versatile instruments used for measuring the mechanical properties of food, the universal testing machine (UTM) stands out. Traditionally used in the field of materials science
and engineering, the possibility of applying UTM for evaluating food textures has gained significant attention in recent years. The UTM can perform compression, tension, bending, and shear tests on food samples, providing objective and quantifiable data on their mechanical properties. Compression testing involves measuring the force required to compress a food sample between two plates, shear testing measures the force required to cut through a food sample, while puncture testing measures the force required to puncture a food sample with a probe. This paper reviews the current state-of-the-art of UTM in the evaluation of food textures, including the types of tests that can be performed, the parameters that can be measured, and the challenges and limitations associated with the technique. The potential of utilizing UTMs in the food industry for quality control
and product development, instead of traditional sensory evaluation methods, is discussed, along with its advantages and disadvantages. Overall, UTM represents a promising tool for the objective evaluation of food textures, and further research is needed to optimize its application in this field
Determination of Compression Response for Various Dried Vegetables
No full textThe texture of food plays a vital role in its overall quality, affecting both sensory experience and functional aspects, such as processing and preservation. To study texture in the field of food science and technology, various analytical methods are used tomeasure mechanical properties such as hardness, cohesiveness, and viscosity. One widely utilized technique for evaluating the texture of solid foods, particularly those with high firmness or brittleness such as dried vegetables, is compression testing. Here, a force is applied to a food sample until it deforms or fractures. In this particular study, dried onions, carrots, and peppers were chosen as test samples to investigate their texture and compression properties. To perform the tests, the researchers employed a Shimadzu AGS-X universal testing machine equipped with a 1 kN load cell capacity. This machine allowed them to compress the samples and measure the force required to achieve a specific deformation. The obtained results revealed that the texture and compression properties of the
dried vegetables were significantly influenced by the specific part of the vegetable being tested. For instance, when examining the dried onions, a notable disparity was observed between the inner and outer parts. The basal plate of the onion, in particular, exhibited much greater hardness compared to the middle portion of the dried onion. Consequently, breaking the sample required a higher compression force. This discovery implies that the texture and compression properties of dried vegetables are closely tied to their inherent characteristics, internal structure, and
composition
О брахистохронных движениях твердых тел с различными ограничениями реакции связи
Get PDFPredavanje po pozivu na Seminaru "Išljinski" Katedre za primenjenu mehaniku i upravljanje Fakulteta za mehaniku i matematiku Moskovskog državnog univerziteta "Lomonosov
Digital Transition of the Maintenance Process: Case of Rail Transport Company
No full textDigital transformation of business activities has outgrown from
competitive advantage to necessity in recent years. Evolution of
information and communication technologies (ICT) has created
the world where electronic business (E-Business), document
management systems (DMS) and enterprise resource planning
(ERP) solutions have become standard, even for micro, small
and medium enterprises (MSME) in developing countries.
Modern businesses focus on implementing data analysis,
business intelligence (BI) and even artificial intelligence (AI)
concepts in their everyday activities, thus the digitalization of
business activities is simply considered as default. Nevertheless,
public companies in developing countries fall behind and
struggle in this transformation process, as usual. Due to various
reasons, they are still in the phase of digitalization, rather than
implementing advanced solutions. Any organizational change
demands unfreezing and mindset redirection, among both
management and executors, which is always challenging,
especially in the public sector. This paper aims to explain the
preconditions and benefits of digital transition of the train
maintenance process, and key challenges in such transformation
New Trends in Engineering Research: Proceedings of the International Conference of Experimental and Numerical Investigations and New Technologies, CNNTech 2023
No full textCompressive and flexural mechanical responses of components obtained through mSLA vat photopolymerization technology
No full textIn recent years, Additive Manufacturing (AM) has become an increasingly popular method in industrial
applications for fabricating components with complex geometries, offering several benefits over traditional
(subtractive) manufacturing methods. Among all available AM technologies, ‘‘vat photopolymerization’’ is still
a reliable approach for manufacturing high-resolution components at relatively small costs. This particular
AM technology is based on the photopolymerization process where 3D objects are created by light-induced
solidification and it has been broadly developed and used in the past decades. Depending on the employed
light source there are three different subtypes of this technology, namely: SLA, DLP, and mSLA. Among all
three listed, the Masked Stereolithography Apparatus (mSLA) technology has emerged as a promising approach
due to the much simpler AM machine construction compared to the other two. However, the mechanical
properties of mSLA components have not been studied extensively, hence there is a lack of knowledge of
how AM process parameters and post-processing treatments affect the final mechanical properties of mSLA
components. This work presents an experimental investigation of the compressive and flexural mechanical
responses of components produced through this relatively new AM technology. A series of static and cyclic
tests were conducted with varying layer thickness and post-curing times. It is demonstrated that a thorough
optimization of the mentioned variables is required to obtain parts with the desired mechanical properties
Variational Approach to 2D and 3D Heat Conduction Modeling
Get PDFThe paper proposes an approximate solution to the classical (parabolic) multidimensional 2D and 3D heat conduction equation for a 5 × 5 cm aluminium plate and a 5 × 5 × 5 cm aluminum cube. An approximate solution of the generalized (hyperbolic) 2D and 3D equation for the considered plate and cube is also proposed. Approximate solutions were obtained by applying calculus of variations and Euler-Lagrange equations. In order to verify the correctness of the proposed approximate solutions, they were compared with the exact solutions of parabolic and hyperbolic equations. The paper also presents the research on the influence of time parameters τ as well as the relaxation times τ∗ to the variation of the profile of the temperature field for the considered aluminum plate and cube
Analysis of Lubrication Regimes for Porous Sliding Bearing
Get PDFThe purpose of this paper is to analyze the lubrication quality of porous sliding bearings, starting from the bearing model and in combination with experimental results aimed at analyzing the lubrication regimes of different working conditions. The separation between the surfaces by the lubricant layer is what determines the regime. The quality and type of lubrication regime are determined by parameters in the mathematical model including typically speed, load, motion, materials, environment, etc., which have an impact on friction. Besides those elements, important parameters such as coefficient of friction (COF) and working temperature are to be measured due to experimental investigations to detect an equilibrium working state. The self-lubrication mechanism in porous metal bearings improves their service life and lubrication processes; however, the COF still varies within a wide interval. This variability can be understood, considering that during bearing operation it operates within a broad range of lubrication regimes. Those findings are explained in the paper by using a combination of calculated parameters according to the bearing model and in combination with our own results of experimental investigations. With the obtained results for particular working conditions, the authors are trying to explain, in the form of a diagram with the limit line as an important outcome of the work, that the lubrication regime for porous metal bearings could arise from boundary lubrication (BL) close to hydrodynamic lubrication (HDL)
One-to-one mapping as a key factor in understanding the cardinality of sets among engineering students.
Get PDFThe use of different task formats (related to the same concept) has proven to be a good strategy
for eliciting cognitive conflicts and opportunities for deeper analysis of responses. Through its application, we
attempted to explore how engineering students deal with tasks related to the concept of set cardinality. The
study involved 269 students from two universities: the University of Belgrade and the University of Novi Sad.
By analyzing students’ responses, we discovered the most common misconceptions in solving such tasks and
why understanding the concept of functions (one-to-one mappings) played a crucial role. The results of this
research indicate the need for a thorough treatment of the concept of functions in elementary and high school, as
understanding this concept serves as a crucial foundation for further acquisition of more complex mathematical
concepts