Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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OCCUPATIONAL HEALTH AND SAFETY RISK EVALUATION OF PM2.5 AIR POLLUTION DURING THE HEATING SEASON IN BELGRADE, SERBIA
No full textBelgrade has faced persistent air pollution for decades, with particulate matter concentrations frequently exceeding World Health Organization (WHO) limits during the heating season. Among major pollutants, fine particulate matter smaller than 2.5 μm (PM2.5) poses particular risks to health and has gained increasing attention in occupational safety and health research. This study examined the frequency of low-wind-speed days and the distribution of PM2.5 concentrations under such conditions to assess monthly risk levels during the heating season. Results show that October, December, and January are periods of elevated occupational health and safety risk. These findings highlight the need for preventive measures, such as shorter outdoor shifts, increased rest breaks, and task rotation, to reduce worker exposure to hazardous PM2.5 levels.under Contract No. 451-03-137/2025-03/20010
Evaluating the Limit States: A Case Study of a Hull Girder
No full textThis work explores the impact of selecting critical thresholds (i.e., limit states), on the loadbearing capacity of large structures. Using the hull girder of a typical inland navigation barge as a
case study, this analysis evaluates the structure's capacity to endure high loads. Modeled as an open box girder made of steel, comprised of plates and stiffeners, the structure is assessed under the most critical load it encounters: the vertical bending moment (BM). The maximum BM that the structure can withstand is calculated using various limit states commonly selected during the structural design of such objects: yield stress, collapse stress, industry-standard allowable stress, full-plastic stress, the Caldwell approach, the Paik-Mansour approach, and the progressive-collapse analysis [1]. The first three consider linear-elastic behavior, while the latter four involve ultimate (nonlinear) limit states that can lead to hull girder collapse and the loss of load-carrying capacity. Also, buckling phenomena is included in analysis [2]. The results demonstrate the safety margin between linear-elastic and ultimate limit states, emphasizing how the choice of structural criteria can significantly influence the designed load-carrying capacity of large structures
Design of Specialised Unmanned Underwater Vehicle
No full textDepending on the diverse characteristics of the aquatic area, its exploration has always been challenging for people carrying out various missions underwater. For these purposes, unmanned undewater vehicles (UUV) provide a solution to minimise risk for researchers and scientists. Unmanned underwater vehicles can operate independently (autonomous underwater vehicles) or be connected with various cables to a ship and controlled by an operator (remotely operated vehicles). Underwater missions are becoming more successful with the development of technology that provides more sophisticated equipment, such as various sensors, cameras, automatic buoyancy control system, sonars, control systems, etc. This paper explains the development of a simple UUV, relying on the use of additive manufacturing (AM) for the majority of components. AM is used and described as a viable solution for this project, suitable even for harsh environments such as the underwater region. Different chapters of the paper solve various challenges in terms of design, implementation and integration of different innovative solutions for manufacturing a reliable UUV while keeping in mind that it must be within the limits of low-budget production. The prototype is represented in the final chapter as a universal UUV that can be easily modularly prepared for different types of missions. The application of unmanned underwater vehicles is defined by the equipment it carries and varies from ocean floor mapping and exploration, underwater infrastructure maintenance, underwater photography, to disabling underwater mines
Artificial Intelligence Application and Scenario Planning Methodology In The Green Economy
No full textThe integration of artificial intelligence (AI) in the green economy presents both opportunities and
challenges in addressing environmental sustainability. This abstract provides a concise overview of the
advantages and drawbacks associated with AI deployment in green sectors. On the one hand, AI technologies
such as machine learning, data analytics, and optimization algorithms offer immense potential to enhance
resource efficiency, optimize energy systems, and facilitate sustainable decision-making processes. By
analyzing large datasets and identifying patterns, AI can optimize energy consumption, streamline waste
management, and accelerate the transition to renewable energy sources with the goal of green economy.
However, the widespread adoption of AI in the green economy also raises concerns regarding data privacy,
algorithmic bias, and job displacement. Additionally, the energy-intensive nature of AI training and
computing poses environmental challenges, potentially offsetting the environmental benefits gained from its
implementation. Therefore, while AI holds promise as a tool for advancing environmental sustainability in
the green economy, careful consideration of its implications is necessary to maximize its positive impacts and
mitigate potential risks
BIM – Search for Information
No full textThe digitalization in the AECO (Architecture, Engineering, Construction, and Operations) sector is often heralded as a revolution in the way of working. However, it turned out to be a gradual evolution of the process. An industry accustomed to monolithic representations containing all necessary data for a certain project phase has a hard time changing its habits. The first digitalization step was creating those documents using a computer. The second step is BIM technology, which has the ambition to remain the final form of digitalization in the AECO sector.
The IFC scheme, which represents basis of the openBIM concept enabling connection among all BIM applications, also represents one monolithic digital model. Conceived to represent one AECO project, the IFC scheme contains all data about the single project. Additional technologies such as Data Dictionary and Data Templates, which add more data structures to the basic model, have been developed to enrich IFC.
Currently, the focus in the BIM community is on models containing all the necessary data that users require. Different kinds of information requirements define what data should be included in models. Most of the effort is focused on including the data in the model, and little on how the data will be extracted from the model. The fact that well-structured data does not represent the whole information is recognized in the ISO 7817 standard, which states that when creating the Level of information need, attention should be paid to who, when, why and to what extent will use information, although it does not specify how to use these prerequisites to search for information.
The paper analyzes the ways to search BIM data structures from the simplest browsing using the BIM viewer to more complex techniques. Existing proposals are considered, and original ones based on the latest BIM developments are given
Pore-scale viscous fingering as a mechanism for pattern formation – a historical overview, application, and the ways of controlling it
No full textViscous fingering instability, as one of the numerous fluid in-stabilities and mechanisms of pattern formation, is very com-mon in different fields of research. First studied experimentallyin an apparatus called a Hele-Shaw cell in 1898, it has beenwidely used, for example, as a model for porous media in lab-oratory testing. This paper provides a brief insight into themathematical model of the Saffman–Taylor instability (porescale viscous fingering) and the situations in which viscous fin-gering can be encountered. Since it is a morphogenetic insta-bility, it is usually considered a nuisance and in recent decadesmany scientists and researchers have focused on the ways toavoid its occurrence. For instance, the petroleum industry hasbeen continuously trying to discover the best solution for itscontrol since viscous fingering limits oil recovery in porousmedia. The review provides a historical overview of the phe-nomena and various methods that have been used to controlthis instability. The final part of the paper gives a summary andthe conclusions that have been drawn as the results of diversestudies.CONTACT Ivana Cvetkovic [email protected] Faculty of Mechanical Engineering, Universityof Belgrade, Belgrade 11000, Republic of Serbia© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributedunder the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permitsunrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on whichthis article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent
Educational building renovation using green roof towards energy savings and decarbonization of cities
No full textThis paper presents an analysis of the possible application of green roof on an existing educational building with a flat roof, through an analysis of the degree of energy efficiency improvement and CO2 emission reduction. The goal of the paper is to show, through the preparation of the energy efficiency report and Energy passport, the green roof as an exceptional tool for ensuring sustainable development, decarbonization and improving the quality of life of people in urban areas. This is important because urban areas have limited space for green infrastructure and high level of pollution. The research also clearly defines the impact of green roof installations on energy savings with the share for heating of 15% and air quality contributing to the about 6% lower CO2 emission, with attached methodological explanations for their application. Economic analysis and profitability of the proposed project are also provided as an additional indication of the relevance of this type of practice. In the economic analysis, the key indicators of the profitability of the investment are studied, in this investigation, the net present value (NPV) and the payback period (PBP) of the green roof project. PBP of 22 years was obtained, but it should not be considered separately of the other benefits of green roofs, which are not measurable in money, such as lower pollution in cities, habitats for pollinators, additional green areas for people, prevention of floods, etc
Structural optimization of a composite structure of a vertical take-off and landing (VTOL) unmanned air vehicle (UAV)
No full textIn order to design the optimal composite structure of a contemporary unmanned air vehicle
(UAV) with vertical take-off and landing (VTOL) capability, a finite element (FE) model was
developed and incorporated into an optimization cycle. Structure is assumed as a layered
carbon-fiber shell, whose lay-up sequence (defined by layer thicknesses and orientations) is
optimized by genetic algorithm (GA). As illustrated in Fig. 1 (left) the beam is constrained at
places corresponding to connections with the wing, and forces are introduced at one end,
simulating worst-case scenario (e.g. a sudden impact). The goal function is the minimal mass,
whereas different constraints (such as failure criterion, or maximal strain) are imposed. The
population is made up of 100 individuals, that are matched and crossed for 50 generations, until
converging to the optimal solution, as represented in Fig. 1 (right). The proposed methodology
can significantly facilitate and accelerate the design process of composite structures present in
aerospace engineering
MASS OPTIMIZATION OF TIMOSHENKO BEAMS BY USING THE PONTRYAGIN MAXIMUM PRINCIPLE
No full textThe mass optimization of axially functionally graded (AFG) circular Timoshenko beams is
considered in this paper for a given fundamental natural frequency. The case of coupled
longitudinal, bending and torsional vibrations is considered based on given boundary
conditions. The Pontryagin maximum principle is applied for shape optimization with respect
to the limited diameter under the constraints of structural integrity and Timoshenko beam
theory. Governing equations are transformed into a system of ODEs and the problem is
formulated as the TPBVP. For the self-adjoined systems all coupled variables except one, are
expressed through state variables, thus the numerical solution is more approachable.
Theoretical considerations are illustrated with a numerical example. In the example,
different boundary conditions and mechanical characteristics of materials are implemented.
The mass reduction is compared for beams with constant cross-sectional profiles and beams
with optimized profiles for the given fundamental natural frequency
Digital image correlation application to structural integrity assessment
No full textDigital image correlation represents a useful, efficient,
and widely applied method of non-contact strain and displacement measuring in various types of structures. It is often
combined with other means of integrity assessment, such as
the finite element method and the use of fracture mechanics
parameters. This paper presents a short overview of digital
image correlation in various fields including mechanical and
civil engineering, biomedicine, and some other, more ‘exotic’
examples. Additionally, some of the examples shown here
perfectly illustrate the applicability of this method to cases
where high levels of detail and accuracy are necessary in
order to measure strain