Periodica Polytechnica (Budapest University of Technology and Economics)
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Case Study: Numerical Investigation of Lateral Stability of Non-prismatic Double Web-tapered Prestressed Reinforced Concrete Girder
Full text linkThis study presents a comprehensive numerical investigation into the lateral stability of non-prismatic, double web-tapered prestressed reinforced concrete girders using advanced finite element modeling (FEM) in ATENA-GiD, validated against experimental results. The analysis examines the influence of key parameters, including initial lateral imperfections (ILI), rubber bearing pad stiffness, concrete tensile strength, load application method, and the effectiveness of fork support restraints. Results reveal that increasing ILI amplifies mid-span lateral displacement by up to 55%, compromising stability. Conversely, stiffer rubber pads improve restraint performance, reducing lateral displacement by 42%, while higher concrete tensile strength decreases lateral displacement by 32% and delays crack formation. Additional parametric studies highlight that the application of eccentric loads, common in experimental and real-world setups, induces secondary torsional effects that reduce lateral stability. A centric load application condition improved performance by reducing lateral displacement by 14%. Moreover, incorporating fully hardened fork supports at girder ends led to a 60% reduction in out-of-plane displacement, demonstrating their essential role in suppressing lateral-torsional buckling. These findings underscore the critical importance of accounting for geometric imperfections, support detailing, load positioning, and material properties in the design of slender, long-span, non-prismatic girders to ensure optimal stability and structural safety
Artificial Intelligence DTC MTPA Strategy Based on Speed MRAS Observer for Electric Vehicle Traction Applications
Full text linkThis paper presents an advanced direct torque control (DTC) strategy incorporating artificial intelligence and a speed Model Reference Adaptive System (MRAS) observer for permanent magnet synchronous motors (PMSMs) used in electric vehicle traction. The studied electric vehicle is equipped with four in-wheel PMSMs, requiring an electric differential to ensure balanced torque distribution and vehicle stability, especially during cornering maneuvers. To reduce system weight and enhance efficiency, two machines on the same vehicle side are powered by a single three-leg inverter, forming a multi-machine single-inverter configuration. A master–slave control structure is adopted to manage this architecture and ensure synchronized operation of all motors. The proposed AI-based DTC combined with the MRAS speed observer significantly improves torque accuracy, dynamic response, and robustness against disturbances. Simulation results obtained using MATLAB/Simulink confirm that the proposed strategy achieves high performance in both transient and steady-state conditions, ensuring reliable traction, enhanced vehicle stability, and improved overall dynamic behavior
On the Tensile Behavior of Heat-treated Hydrogen Charged 316L Stainless Steel
Full text linkIt is well established in the literature that the precipitation of different carbide types and intermetallic phases in stainless steels can lead to drastic consequences in their mechanical and corrosion behavior. Chromium carbide particles precipitate at grain boundaries, creating chromium depletion zones that expose the stainless steel to high corrosion penetration in harmful working atmospheres. The aim of this work is to evaluate the effect of electrolytically charged hydrogen on the mechanical behavior of heat treated AISI 316L austenitic stainless steel samples. To achieve a homogeneous distribution of carbides, specific heat treatments were conducted before tensile tests. Subsequently, a group of heat-treated samples were hydrogen-charged. After tensile tests carried out at high (0.003 s−1) and low (0.000003 s−1) strain rates, the resulting fracture surfaces exhibited mixed behavior in hydrogen-charged samples, i.e., ductile-brittle, in comparison with the ductile morphology obtained in uncharged ones. Additionally, in hydrogenated samples, cracks were associated with fine chromium carbides. Coincidentally, there was a ductility loss in hydrogen-charged samples, which was not observed in uncharged ones. In order to identify hydrogen-carbide interactions, combined studies of Differential Scanning Calorimetry (DSC) and a selective metallographic technique made it possible to identify grain boundaries and carbides/matrix interfaces as the main hydrogen traps. Finally, regarding strain rate effects on mechanical properties, it could be stated that when the strain rate decreases, the embrittlement effect of hydrogen is more explicitly manifested in conjunction with a microstructure sensitized by heat treatments and revealed by the mixed mode of fracture in hydrogen-charged samples
Mechanical and Microstructural Characterization of a Titanium-based Ti-6Al-2Cr-2Ni Alloy Produced by SPS Sintering for Use in the Aerospace Industry
Full text linkTitanium-based alloys are widely applied in the aerospace industry thanks to their excellent strength-to-weight ratio, good corrosion resistance and thermal stability. In this study, a Ti-6Al-2Cr-2Ni alloy was elaborated by Spark Plasma Sintering (SPS), a technique derived from powder metallurgy that enables rapid, controlled densification. Sintering was carried out at 1000 °C under 30 MPa for 8 minutes in an inert atmosphere. A thermal annealing treatment at 550 °C was then applied to optimize microstructure and mechanical properties. Microstructural characterization by scanning electron microscopy (SEM), combined with EDS elemental analysis, revealed a significant reduction in porosity and progressive homogenization of the alloying elements after treatment. X-ray diffraction (XRD) confirmed the presence of a majority of α-Ti phase, associated with intermetallic compounds. Mechanically, Vickers microhardness measurements showed an increase in hardness after annealing, while instrumented indentation enabled Young's modulus to be reliably determined. These results indicate that the Ti-6Al-2Cr-2Ni alloy developed by SPS is a promising alternative to standard alloys such as Ti-6Al-4V, offering improved microstructural controllability, interesting mechanical properties and thermal optimization potential for advanced aerospace applications
Interjú Vizkelety Andrásné Ecsedy Judittal, aki 2025 márciusában a Magyar Érdemrend tisztikeresztje polgári tagozat kitüntetésben részesült: Milyen magyar könyvet nyomtattak a XVIII. században Eldorádóban?
No full textVizkelety Andrásné Ecsedy Judit bibliográfus, bibliográfus, tudományos kutató, az MTA doktora, szűkebb szakterülete a magyarországi könyvtörténet, nyomdászattörténet, a Magyar Tudományos Akadémia doktora, a nemzeti könyvtár nyugalmazott tudományos kutatója 2025. március 15-én a Magyar Érdemrend tisztikeresztje polgári tagozat kitüntetésben részesült tudományos tevékenysége elismeréseként
A stratégia is lehet közérthető? A Gödöllői Városi Könyvtár újszerű stratégiaalkotási folyamata
No full textCan a strategy be reader-friendly? Can a mission statement be effectively communicated through a comic strip? Are such approaches mere passing trends that undermine professional standards, or can they be considered innovative methods for conveying traditionally boring and complex management tools in a more accessible and engaging manner? The Gödöllő City Library approached its upcoming strategic cycle by rigorously adhering to all fundamental steps of strategic planning, and published its new strategic plan in 2024. It sought to formulate a longterm plan (2024-2030) that would not only provide a clear direction and task allocation for staff members, but also present the institution's values, goals, and citizen-focused services in a way that is understandable to a wider public audience. By combining professional rigor with creative communication, the library aimed to bridge the gap between strategic intent and everyday relevance. The article detailing this comprehensive planning process concludes with a visually compelling infographic designed to enhance accessibility and facilitate understanding.Létezik olyan, hogy olvasóbarát stratégia? Képregényben elmesélt küldetésnyilatkozat? Újfajta divathóbort, a szakmaiság megcsúfolása, lebutítása, vagy korszerű megközelítése és érthető csomagolása egy száraz és unalmas menedzsmenteszköznek? A Gödöllői Városi Könyvtár a stratégiai tervezés minden fontos lépését betartva megpróbálta oly módon megalkotni a következő ciklusra vonatkozó, 2024-ben kiadott hosszú távú (2024–2030) tervét, hogy az mind a munkavállalók számára világosan kijelölje az útvonalat és az ahhoz tartozó feladatokat, min a szélesebb közönség számára közérthetővé tegye, milyen értékeket képvisel a könyvtár, melyek a jövőbeni tervei, milyen lehetőségeket kínál állampolgárainak. A tervezési munkát részletesen bemutató cikkhez mellékletként kapcsolódó látványos infografika segíti a könnyebb befogadást
