Mechanical Design (Slovakia)

The transition to renewable fuels necessitates reliablediagnostictools for monitoring engine health and lubricant stability. This studyintroduces an integrated methodology that combines vibration signatureanalysis with oil degradation indices to evaluate the long-term performanceof a single-cylinder diesel engine operated with Jatropha-based biodieselblends (10%, 20%, and 30% v/v). Over 100 h (h) of operation, vibrationdata were recorded using fast Fourier transform analysis, while oilcondition was monitored through viscosity, density, and infrared spectroscopyto quantify soot, oxidation, nitration, sulfation, and additive depletion.Statistical evaluation, including Pearson correlation, revealed stronginterdependencies between vibration amplitude and chemical degradationmarkers, confirming a direct mechanical–chemical linkage. Amongall blends, the 20% biodiesel blend exhibited the most favorable performance,showing the lowest vibration amplitude, minimal additive depletion,and stable physicochemical oil properties, thereby aligning closelywith baseline diesel. These findings establish a novel dual-parameterdiagnostic framework for predictive maintenance, offering significantpotential for extending the lubricant life, reducing downtime, andsupporting the adoption of sustainable biodiesel in compression ignitionengines. To the best of our knowledge, this is the first study todirectly correlate vibration signatures with FTIR-based oil degradationindices to establish a dual-parameter predictive diagnostic frameworkfor biodiesel-fueled engines. The study also develops a regression-basedpredictive model (R2 = 0.81, p < 0.05) linking vibration amplitude with oxidation and viscosityindices, establishing a foundation for real-time predictive maintenanceapplications.

Timely cancer detection is crucial for reducing mortality rates associated with delayed diagnosis and treatment. This study presents a novel, non-invasive tumor detection technique that integrates finite element analysis (FEA) with machine learning (ML) models. A piezoelectric sensor, developed using vibration absorber phenomena, was designed to detect changes in tissue stiffness caused by tumors. The sensor's interaction with soft tissue of varying Young’s modulus (9 to 185 kPa) was simulated to mimic the properties of cancerous tissue. Modal and harmonic analyses using ANSYS software, including indentation trials, were conducted to study the sensor’s response to stiffness variations, creating a dataset based on tumor sizes (5, 10, 12, 15, 17, 20, and 25 mm in diameter) at different vertical and horizontal distances from the tissue surface to the tumor center, simulating various growth stages and depths. The collected data were used to train two machine learning models: a recurrent neural network (RNN) for precise tumor localization and sizing and a feedforward neural network (FNN) to estimate tissue stiffness through sensor absorber frequencies. The proposed methodology demonstrated promising results, with a minimum error of 0.04 mm in tumor size estimation and 0.0319 kPa in stiffness detection. This approach offers potential improvements in early tumor detection by providing accurate and noninvasive diagnostics, particularly in resource-constrained environments.

The refrigeration characteristics in a vortex tube are experimentally investigated to promote their application in aerospace engineering. The experiments focus on the effects of the inlet pressure (Pin=0.2 to 0.7 MPa), inlet temperature (T=20 to 70°C), cold outlet pressure (Pc=0.4 to 0.7 MPa), and the cold mass fraction (μ=0.1 to 0.9). The experimental results reveal that, maintaining the same cold mass fraction, elevating the inlet pressure below 0.4 MPa leads to a substantial increase in temperature reduction and cooling effectiveness. This enhancement becomes less pronounced when the inlet pressure surpasses 0.4 MPa. Raising the inlet temperature can enhance temperature reduction and cooling effectiveness. Increasing the cold outlet pressure tends to decrease the actual temperature drop. Although its influence on temperature efficiency is minimal, significant improvements in adiabatic efficiency and coefficient of performance are observed for cold mass fractions exceeding 0.6. Across all test conditions, there exists a critical cold mass fraction point that optimizes the refrigeration process. An empirical correlation formula was derived from experimental data, and its accuracy was validated through a comparative analysis between the experimental results and the predicted values.

In this study, a novel control framework for the collaboration of an aerial robot and a ground vehicle that is connected via a taut tether is proposed. The framework is based on a leader-follower paradigm. The leader follows a desired trajectory while the motion of the follower is controlled by an admittance controller using an extended state observer to estimate the tether force. Additionally, a velocity estimator is also incorporated to accurately assess the leader’s velocity. An essential feature of our system is its adaptability, enabling role switching between the robots when needed. Furthermore, the synchronization performance of the robots is evaluated through quantitative analysis using the RMS position error metric and circular variance metric that is used in the mirror game to measure synchronization in human interactions. Similar to human-human interactions, we have observed that robotic agents can effectively guide one another based solely on interaction cues and adapt as needed. Our findings demonstrate the remarkable ability of robots to closely follow each other using a velocity estimation approach, without the reliance on sensors. This work contributes to the field by advancing robotic collaboration capabilities under limited sensor conditions, capitalizing on the inherent sensing capabilities of the robots, and providing a versatile platform for the study of cooperative behaviors in artificial systems.

The attachment points research is fundamental to the aircraft lightning zones and subsequent protection design, which is great significance for lightning protection. Aiming at the problems of few reference cases, long time and high cost of testing and many simulation gestures of aircraft, the aircraft with large length-to-diameter ratio is researched, a simulation model is established which including lightning environment, lightning induced electric field intensity distribution and streamer generation criterion, and the attachment point of typical attitude is calculated. And the simulation results were compared with test results to verify the effectiveness and accuracy of the simulation method. Further simulation analysis shows that the characteristics of roll, yaw and high pitch angle are not sensitive, and the attachment characteristics of the aircraft with an aspect ratio greater than 6 and a flight attitude greater than 10° are proposed. The attachment point simulation of the aircraft with a large length-to-diameter ratio is optimized.

Poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), as a highly hydrophilic as well as biocompatible material, has been widely used in biomedical applications. In this study, the friction reduction and wear resistance of HXLPE were improved by grafting PMPC on its surface. However, the PMPC will be sheared off during friction, which is difficult to meet the long-term service requirements of artificial joints. This can be achieved by improving the lubrication environment to minimize PMPC shedding. To simulate the human lubrication environment, free PMPC (lubrication factor) and Cu 2+ (transition group metal ion catalyst) were added to neonatal bovine serum (NBCS). When the friction pair consisting of grafted PMPC-modified HXLPE and Cu/ZrO 2 ceramics is rubbed therein, the grafted PMPC interacts with the free PMPC, while Cu 2+ catalyzes the oxidative hydrolysis of serum proteins into carbon-containing small molecules and adsorbs on the surface of the Cu/ZrO 2 ceramics to form a carbon-rich lubrication layer. The composite lubrication layer consisting of grafted-free PMPC and carbon-rich lubrication layer provides good load-bearing and lubrication properties at the friction interface. And the wear rate is reduced by 45% compared to rubbing in deionized water. This technique can reduce the shedding of grafted PMPC state and improve the load-bearing performance of the interfacial lubrication layer, thus reducing the wear of HXLPE and prolonging the service life of the artificial joint.

Heat and mass transfer rate by using nanofluids is a fundamental aspect of numerous industrial processes. Its importance extends to energy efficiency, product quality, safety, and environmental responsibility, making it a key consideration for industries seeking to improve their operations, reduce costs, and meet regulatory requirements. So, the principal objective of this research is to analyze the heat and mass transfer rate for three-dimensional magneto hydrodynamic nanoliquid movement with thermal radiation and chemical reaction over the dual stretchable surface in the existence of an inclined magnetization, and viscous dissipation. The flow is rotating with constant angular speed ω∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upomega }^{*}$$\\end{document} about the axis of rotation because such flows occur in the chemical processing industry and the governing equations of motion, energy, and concentration are changed to ODEs by transformation. The complex and highly nonlinear nature of these equations makes them impractical to solve analytically so tackled numerically at MATLAB. The obtained numerical results are validated with literature and presented through graphs and tables. Increasing the Eckert number from 5≤Ec≤10,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\\le Ec\\le 10,$$\\end{document} a higher Nusselt and Sherwood number was noted for the hybrid nanofluid. By changing the angle of inclination α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}, the Nux\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${Nu}_{x}$$\\end{document} performance is noted at 8% for nanofluid and 33% for hybrid nanofluid. At the same time, Shx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${Sh}_{x}$$\\end{document} performance of 0.5% and 2.0% are observed respectively. Additionally, as the angle of inclination increases the skin friction decreases and the chemical reaction rate increases the mass transmission rate.

For patients living with intestinal or urinary stomas, skin barriers play an essential role in protecting the peristomal skin and preventing peristomal complications. Convex baseplates press into the peristomal skin and are suitable for retracted stomas that do not protrude, peristomal skin with creases, folds, or dips, and stomas where frequent leaking can occur with flat pouching systems. However, there is a lack of data on the magnitude and location of tension applied to the abdomen by convex baseplates. We evaluated the impact of a range of convex baseplates applied to a simulated stoma site. A comparative finite element analysis investigation was conducted to evaluate the impact of eight different convex stoma system baseplates applied to an idealised flat abdomen, representing skin, subcutaneous tissue, and musculature layers. The baseplates considered had varying convexity with depths of 3.5 mm and 7 mm and internal structural diameters between ~30 mm and ~60 mm. The convex product range provided tension in the skin (maximum principal strain) and compression through the fat layer (minimum principal strain). Large differences in the locations and magnitudes of skin tension and fat layer compression were seen between the baseplates under analysis, with both the depth and diameter of convexity influencing the strain experienced across the abdominal topography. The results generated highlight the importance of having an appropriate range of convexity products available and selecting an appropriate option for use based on the stoma type and condition of the peristomal skin.

The unique mechanical properties and wear resistance of HDPE give it the potential as an alternative to frictional material. The current research focuses on using hybrid nanoparticles with various loading fillers to determine the best additive contents. The mechanical and tribological characteristics were examined and evaluated. The HDPE nanocomposite samples containing 0.5, 1.0, 1.5, and 2.0 wt.% filling content of Al2O3 nanoparticles (NPs) and 0.5, and 1.0 wt.% of graphene nanoplatelets (GNPs) were fabricated. The results showed a good enhancement in the mechanical and tribological properties of HDPE composites with the presence of nano additives. The HDPE nanocomposites recorded the best performance with a loading amount of 2.0 wt.% with an equal ratio of hybrid nanofiller Al2O3 NPs and GNPs.