Periodica Polytechnica (Budapest University of Technology and Economics)
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A Self-adapting Pixel Antenna - Substrate Lens System for Infrared Frequencies
Get PDFIn this work, we propose a concentrator lens - antenna arrangement, potentially suitable for infrared sensing and energy harvesting rectenna systems. The structure consists of a pixel antenna, self-adapting for the direction of the incident infrared radiation, and a concentrator lens, both optimized for the mid-infrared spectrum. The silicon substrate lens is situated above the pixel antenna, enabling the concentration of the incident light on the antenna; silicon was chosen due to its transparency in the IR spectrum. We examine how various parameters of the lens, in conjunction with the different states of the pixel antenna, affects the performance of the system. The simulations show that the gain of the arrangement increases considerably in correlation with the radius of the lens. The results suggest that the energy conversion efficiency of infrared rectenna systems can be enhanced by several orders of magnitude with the utilization of the proposed arrangement
A New Modeling Approach and Comprehensive Monitoring of Electrical Faults Through Spectral Analysis in DSIM
Get PDFThe objective of this study is to evaluate the dependability of double-star induction machines by employing meticulous monitoring and intelligent handling of potential electrical malfunctions that may arise during their functioning. Specifically, the research delves into the examination of three distinct fault types: rotor bar breakage, stator phase opening, and inter-turn short circuit. Utilizing a mathematical model developed in the natural reference frame (abc), our aim is to comprehensively delineate both normal and faulty operational scenarios. To categorize and gauge the gravity of identified faults, we employ a methodology rooted in spectral analysis. In order to ensure continuous machine operation, especially in instances of stator phase opening, our proposed mitigation approach entails intentionally opening a secondary phase positioned at a 90-degree angle to the faulty phase. This strategic alteration transforms the machine into a dual two-phase configuration. Through rigorous simulation analyses, our findings underscore the efficacy and pragmatic viability of the devised fault detection technique, offering valuable insights into the domain of electrical machine reliability and fault management
Improved Method for Determining the Feed Influence on the Tangential Cutting Force During Re-drilling, Countersinking and Boring Based on the Small Sample Theory
Get PDFMethods of determining the tangential cutting force are analyzed in the work, including finite-element simulation models, the use of neural networks, analytical methods, and methods of natural experiments. A method for evaluating the influence of feed on the tangential component of the cutting force is proposed, which can be applied to test new tools, tool plates for a certain group of materials. The main advantage of the proposed method is the limited number of experiments and processing of the obtained data according to the theory of a small sample. In this study, the proposed method was used to determine the influence of countersinking feed on tangential cutting force. The basis of the approach is probabilistic and statistical methods and data processing criteria. An assessment of the homogeneity of the results of experimental studies was carried out, the law of distribution of the tangential cutting force, as well as the characteristics of its dispersion, were established. An approach to estimating the maximum value of the tangential component of the cutting force based on the maximum value is presented. This method is universal and can be used for drilling, countersinking, boring and other types of processing
Investigation of the Holy Crown as a Metal Structure
Get PDFThe article analyses the crown of Hungarian kings, a crown of sacral importance, as an engineered metal structure resulting from a technological process. Its composition revolves around two primary components: the cross-strap and the hoop. The cross-strap consists of the actual cross-strap stems and the cross. As for the hoop crown, it comprises the hoop, the diadem (a pediment), and the pendants. The assembly sequence of these parts and sub-parts are described, how the hoop and the cross-strap were aligned and how the sub-parts—the diadem, pendants, and various decorative elements—were assembled and aligned with the primary components. A 3D fully parametric CAD model was used for the analysis. Results show that the eightfold division of the hoop is accurate and that the cross-straps are made with a small degree of inaccuracy, suggesting that they were developed independently. Alignment of the hoop was achieved by asymmetrical cutting, to align with the centerline of the back cross strap stem. The diadem, pendants, and other decorative elements, although fixed to the hoop in a coherent manner, are aligned with the cross-strap. Consequently, the cross-strap emerges as the defining element of the unified Holy Crown, around which all other components are harmoniously aligned
Shear Strength Evaluation of Concrete Beams with FRP Transverse Rebar
Get PDFRebar corrosion in traditional reinforced concrete (RC) components may lead to a decrease in service life and carrying capacity. This condition is one of the reasons of the growing popularity of Fiber Reinforced Polymer (FRP) rebars as a corrosion-resistant alternative, particularly in RC infrastructure projects. Because the material properties and behavior of FRP rebar are very different from conventional steel rebar, the calculations used for reinforced concrete with conventional steel reinforcement should be updated for this material. The aim of this study is to propose a new shear strength prediction model for RC beams with transverse steel rebar in order to calculate the shear strength of RC beams with FRP transverse rebar according to TS-500, which is the Turkish Building Code. To achieve this goal, Finite Element Method (FEM) models were created for 27 RC beams with FRP transverse rebars and 9 RC beams without transverse rebars. Furthermore, for RC beams with FRP transverse rebars, a prediction model has been developed. Additionally, 13 prediction models obtained from regulations or scientific studies were compared to the proposed prediction model using a database of 105 tests obtained from previous experimental studies. It was observed that the proposed prediction model provides more consistent results with the test database from the literature compared to the models suggested by other regulations or studies. Therefore, by modifying the shear strength relations recommended in TS-500 for RC beams with transverse steel rebar, they can also be applied to RC beams with transverse FRP rebars
Phytochemical Profiles, in vitro Antioxidants, and Anti-inflammatory Activities of Flowers and Leaves of Lantana camara L. Grown in South of Tunisia
Get PDFThe current study assesses the photochemical profiles, the in vitro antioxidant (2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), reducing power ferric and silver nanoparticule) and anti-inflammatory activity of Lantana camara L. leaves and flowers collected from the South of Tunisia. Bioactive extracts of two organs were prepared through an ultrasound-assisted extraction in ethanol. Herein, multivariate statistical analysis was performed to define the relationship between biological activities and the bioactive molecules content and composition. Phytochemical profiling showed higher phenolic and flavonoids contents in leaves extracts than in those obtained from flowers, while the condensed tannins was absent in both organs. LC-MS analysis identified 16 and 15 phenolic compounds from flowers and leaves extracts, respectively. The flowers extract was especially rich in Kaempferol, luteolin-7-O-glucoside, quinic acid and apigenin-7-O-glucoside. Kaempferol, luteolin-7-O-glucoside, quinic acid and syringic acid were identified as the prevalent compounds in leaves extract. The latter exhibited the highest DPPH and ABTS radical scavenging potentials. Whereas flowers extracts revealed the highest reducing potential of ferric and silver ions. However, the leaves and flowers extracts are unable to protect bovine serum albumin (BSA) from thermal denaturation. Furthermore, significant correlations (p < 0.05) were recorded between phytochemical profile and biological activities, as well as between different antioxidant studied assays. The obtained results present practical data for the potential application of L. camara as a sustainable source of multi-functional molecules in food and medicinal industries
Investigation of the Bending Properties of Ex situ Functional Metal Foams
Get PDFIn each industry, compromises have to be made when choosing materials. Lower-density materials have a significant advantage in the automotive sector, especially due to rising fuel prices, since weight reduction can lower overall fuel consumption. The advantageous properties of metal foams, such as low density, high specific strength, and excellent energy absorption, should be researched and exploited in as many areas and ways as possible. This research aims to perform and evaluate the bending tests of ex situ functional metal foams: aluminum alloy matrix (AlSi7Mg) was used, which was filled with Ø2.5–3.0 mm lightweight expanded clay aggregate particles and surrounded by thin-walled aluminum tubes (AlMgSi0.5) with a wall thickness of 2 mm and an outer diameter of Ø32 mm. Empty tubes, foam-filled tubes (with and without structural epoxy adhesive) and metal matrix syntactic foams were compared based on their flexural strength and energy absorption capacity. Quasi-static three-point bend tests were carried out up to 25 mm deflection. The foam-filled tubes with epoxy adhesive showed an average of 6% increase in flexural strength compared to the foam-filled tubes without adhesive and a 145% increase compared to the metal matrix syntactic foams
Investigation of 3D Printed Underwater Thruster Propellers Using CFD and Structural Simulations
Get PDFUnmanned Surface Vehicles (USV) and Autonomous or Remotely Operated Underwater vehicles (AUV, ROV) are developing and spreading rapidly in various industries. A common feature of these vehicles is that they are propelled by small plastic (or metal) propellers in most cases. Additive manufacturing can offer an excellent opportunity for rapid prototyping and the development of new models. This paper aims to investigate the fundamental aspects to be considered in the geometric design and manufacturing of small (diameter less than 100 mm) PLA (Polylactic acid) propellers 3D-printed using Fused Filament Fabrication (FFF) technology. In-service deformation of 3D-printed PLA ducted propellers with average geometry was investigated to determine the effect on the thrust and torque on the blades. For this purpose, one-directional FSI (Fluid Solid Interaction) simulations were performed using CFD (Computational Fluid Dynamics) and structural simulations. The propeller CAD geometries were generated using an in-house MATLAB script. The variable parameters of each version are the thickness, skew, and rake of the propeller blades. For the structural simulations, it was considered that the material properties of PLA parts printed with FFF technology depend on the print orientation. The results of the simulations show that except for extreme geometries (e.g., thin blades, skew, or rake more than 10°), the deformation of small PLA ducted propellers is not significant. CFD studies of the deformed geometries have shown that the resulting deformation has no significant effect on the thrust and torque of the propeller and thruster
Friction and Wear of the Piston Ring – Cylinder Liner System with Artificially Aged Ultra-low Viscosity Engine Oils
Get PDFThis study aims to investigate the performance of artificially aged prototype engine oils through friction and wear experiments. Experiments were performed on a piston ring – cylinder liner model system with boundary conditions derived from real-life operating conditions. The experimental design implemented two prototype oils (SAE 0W-12 and 0W-16) in unaltered and artificially aged form. An additional fully formulated off-the-shelf engine oil (SAE 0W-20) was also aged and analyzed as reference. Oil samples were artificially aged in a custom rig, to simulate long-term in-engine use through thermal cycling at 180 °C. Fourier Transformed Infrared Spectroscopy of the lubricant samples highlighted a depletion of zinc dialkyl-ditiophosphate antiwear additives in all cases, which is comparable to a selected in-service oil. Oxidation was also measurable, albeit lower compared to the in-service sample. Averaged friction coefficients showed a ranking of aged 0W-12 < aged 0W-16 < unaltered 0W-12 < unaltered 0W-16. A decrease in surface roughness was experienced with aged oil samples, whereas unaltered 0W-16 oil produced an unexpected transition in the wear phenomenon and resulted in severe wear
Investigating the Site Response Variability of Deep Sedimentary Column Induced by Varying Soil Friction Angles
Get PDFEnsuring the danger level for sustainable development requires a proper ground response analysis with reliable geological properties of deep sediment deposits up to bedrock. The seismic assessment procedure commonly dealth with the upper 30 meters of soil, overlooking the influence of deeper sediment layers. This study performs the seismic response of an entire soil column extending to bedrock, accounting for the soil frictional angle variability. A one-dimensional nonlinear ground response analysis was conducted using 28 earthquake records, with soil friction angles ranging from 10 to 60 degrees. The results highlight the nonlinear behavior of soils, particularly the modification of shear modulus and damping ratio with depth, influenced by changes in frictional angle and effective vertical stress. It indicates that the 10° frictional angles produce a minimum spectral acceleration demand, primarily due to the high energy dissipation in the over-softened upper layer, hence, reduction in peak ground acceleration (PGA). While a 30° friction angle produces high spectral acceleration at short period in shallow depth. The seismic response resulted in a 0.54 times decrease in peak acceleration in the ground relative to bedrock, highlighting the significance of deep soil investigation. This study shows that different friction angles present a greater understanding of seismic site response, leading to better hazard assessment insights