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EFFECT OF APPLICATION A MIXTURE OF REFRACTORY FILLERS AND ORGANIC ADDITIVES ON THE QUALITY OF PROTECTIVE COATINGS
No full textThe paper presents the results of research on the effect of a mixture of different fillers: based on cordierite and talc, cordierite and mullite, as well as cordierite and zirconium silicate on the cavitation resistance of protective coatings. Various coating compositions and production procedures were investigated. Special emphasis in the research was given to the influence of organic additives on the sedimentation stability of the coating. The quality of the coating was tested using the ultrasonic vibration method according to the ASTM G32 standard. Formation and development of surface damage were monitored by scanning electron microscope. Based on the loss of mass and the change in the morphology of the coating surface, the possibility of applying this type of coating for the protection of metal structures in metallurgy and mining was assessed. The special importance of these coatings is their non-toxicity and application of water-based solutions
Managing fuel consumption and emissions for hybrid electric vehicles through optimization of engine operation
No full textThis paper presents a multi-objective optimization framework for improving internal combustion engine performance in hybrid electric vehicles, specifically targeting the minimization of fuel consumption and emissions (CO, NOx, HC, PM). The proposed method integrates normalized objective functions with weighted factors to develop a unified performance index, facilitating the simultaneous optimization of multiple conflicting objectives. Utilizing the NSGA-II algorithm, a diverse set of Pareto optimal points is generated, each representing different trade-offs between the objectives. The study’s results demonstrate significant improvements in engine performance through the application of the unified ICE operation map, showcasing a notable reduction in emissions with only a slight increase in fuel consumption. The methodology was validated via MATLAB simulations on two case studies involving parallel and series hybrid electric vehicles, employing a custom synthesized drive cycle for energy management strategy evaluation. The unified map enabled real-time control and efficiency improvements by balancing different emission parameters, thus optimizing ICE operation across various conditions
DIGITAL IMAGE CORRELATION-ENABLED DIGITAL TWIN FRAMEWORK FOR STRUCTURAL INTEGRITY ASSESSMENT OF WELDED STEEL PIPELINES
No full textEnsuring the structural integrity of welded steel pipe networks that operate under fluctuating pressure and temperature remains a core challenge for mechanical engineers. Point-based sensors capture only a fraction of the complex strain fields that develop around welds, elbows, and other stress concentrators, limiting the predictive accuracy of numerical models used for fitness-for-service evaluations. From a digital image correlation (DIC) perspective, the solution lies in coupling high-resolution, full-field measurements with continuously updating computational twins. This paper presents a practitioner-oriented concept in which a compact 2D DIC module, comprising an industrial camera, LED illumination, and a graphics board, acquires displacement data directly on the pipe surface. Indicators, such as equivalent plastic strain, wall ovality, and local curvature change, serve as update inputs to a physics-informed twin that combines nonlinear finiteelement mechanics with data-driven parameter estimation. Planned verification includes laboratory cyclicloading studies and numerical sensitivity analyses to establish permissible correlation noise, optimal update frequency, and convergence criteria for critical load assessments. By integrating field-deployable DIC instrumentation with an adaptive digital twin, the proposed framework offers a realistic, low-latency pathway for condition-based maintenance of pressure pipeline and aligns with emerging industry standards for assetintegrity management
Implementacija koncepta iterativnog učenja upravljanja u sistemu sa zatvorenom povratnom spregom
No full textIterativno učenje upravljanja (Iterative Learning Control - ILC) predstavlja strategiju upravljanja zasnovanu na podacima, namenjenu sistemima koji u svom funkcionisanju neprekidno ponavljaju svoje referentne trajektorie i uslove rada. Primera radi, takvu prirodu često imaju robotski sistemi u proizvodnji. Osnovna ideja je da sistem, učeći iz grešaka u prethodnim iteracijama, formira ILC signal, odnosno, kompenzacionu komponentu upravljanja koja koriguje ukupan upravljački signal i time poboljšava preciznost praćenja. U ovom radu se analiziraju različiti pristupi sinteze i implementacije ILC signala u sistemima sa zatvorenom povratnom spregom, sa posebnim osvrtom na serijsku i paralelnu implementaciju ILC signala. Rezultati pokazuju da serijska implementacija može da ponudi značajne prednosti u postizanju željenih performansi sistema
Influence of Geometry Parameters on Shaft’s Load-Carrying Capacity
No full textThe load-carrying capacity of shafts is an important feature in the design and performance of machinery. This paper presents a comprehensive study aimed at understanding and quantifying the influence of geometry factors, including shaft diameter and the position of load between shaft supports, on the shaft’s load-carrying capacity. The load-carrying capacity criterion is the fatigue safety factor. This paper offers a systematic exploration of the influential geometry factors affecting shaft load-carrying capacity, individually and in combination. The paper concludes by considering the simultaneous influence of all the aforementioned factors. A new factor is introduced, representing the effect of geometry parameters. This factor allows for a holistic approach to shaft design, enabling engineers to make informed decisions that maximize load-carrying capacity with the changing geometry of shafts
New error estimates for the conjugate gradient method
No full textThe conjugate gradient method is the default iterative method for the solution of linear systems of equations with a large symmetric positive definite matrix
. The development of techniques for estimating the norm of the error in iterates computed by this method has received considerable attention. Available methods for bracketing the
-norm of the error evaluate pairs of Gauss and Gauss–Radau quadrature rules to determine lower and upper bounds. The latter rule requires a user to allocate a node (the Radau node) between the origin and the smallest eigenvalue of the system matrix. The determination of such a node generally demands further computations to estimate the location of the smallest eigenvalue; see, e.g., Golub and Meurant (1997), Golub and Meurant (2010), Golub and Strakoš (1994), Meurant (1997), Meurant (1999). An approach that avoids the need to know a lower bound for the smallest eigenvalue is to replace the Gauss–Radau quadrature rule by an anti-Gauss rule as described by Calvetti et al. (2000). However, this approach may sometimes yield inaccurate error norm estimates. This paper proposes the use of pairs of Gauss and associated optimal averaged Gauss quadrature rules to estimate the
-norm of the error in iterates determined by the conjugate gradient method
Structural response of Autoclave due to vibrations and optimisation of its supports by spring elements
No full textThis paper will present a novel approach to supporting a piece of process equipment subjected to long-term exploitation conditions, with the main goal of improving its reliability and safety. Optimising the supports of the process equipment (in this particular case, 16 autoclaves used for coal drying) began by measuring the load at the support points. It was followed by an analysis based on good engineering practice to develop a new technical solution. The old support solution represented a rigid connection between the autoclave envelope and the supporting structure. Meanwhile, the new approach introduced spring supports, thus providing flexible connections between the Autoclave and the structure. This flexibility ensures that the load on the vessel's shell is reduced significantly and that stress distribution at the support points is uniform. Simultaneously, the load distribution in the structure's support zone is significantly more favourable. The economic benefit of such an approach and a reflection on sustainability are also discussed
Assessment of students’ productivity in context of indoor environmental quality and personal factors
No full textThis study investigates the impact of personal factors on students’ productivity and relation with Indoor Environmental Quality (IEQ) parameters through thermal comfort in a university classroom. The research is based on experimental research involving measurements, 240 productivity tests created for the purpose of the research and participation of 99 respondents. Paper proposes a novel approach, correlating personal occupants’ parameters with thermal comfort and Indoor Air Quality (IAQ) parameters that affect productivity. The novel approach implies the inclusion of all experimentally measured parameters that affect productivity in the Predicted Mean Vote (PMV) calculation, with the aim of distinguishing the impact caused by personal factors alone. This approach has not been used before and presents a significant gap between the existing prediction calculation models in literature and results obtained in real environments. The differences between calculated and measured productivity in real environments can be substantial, reaching over 80%. Approximately 80% of measured productivity values within the PMV range of −0.25–1 are impacted by personal factors. The importance of personal factors might be greater concerning how often they affect productivity, as opposed to the extent of their influence.Project of Technological Development under Grant number 451-03-65/2024-03/200105 from 05.02.2024
Conceptual Design And Optimization Of Wing Bomb using OpenVSP - Open-Source Program For Computer Modeling
No full textThis paper will present the process of creating a wing bomb model. This UAV is completely designed in OpenVSP and analyzed in the VSPAERO tool. These analyses are very important to get preliminary results that will be used for the next steps of the design and the optimization of the wing bomb. During the development of the conceptual design of this UAV, it was necessary to create several different versions of the model. The OpenVSP program was chosen because it allows engineers to quickly and easily create and modify a model of aircraft
Fixed points results in S-left complete topological spaces and quasi b-metric spaces
No full textIn this paper, we presented the results for extended nonlinear contraction defined on
S-left complete topological spaces. Our results generalize earlier results in literature.
Also, we obtain the fixed point theorem for extended nonlinear contraction defined
on quasi b-metric spaces. This result extended recent results of Pasicki, obtained for
dislocated metric spaces.Grant number 451-03-137/2025-03/200105–4.2.2025