Periodica Polytechnica (Budapest University of Technology and Economics)
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Development and Characterization of Novel Green Cutting Fluids with Nano-additives
Get PDFIn this current investigation, novel cutting fluids developed through a unique combination of food grade emulsifiers, plant based additives (EA) and nano particles (NP) as cutting fluid additives in corn oil (CO) based vegetable oil. Five dissimilar corn-based green cutting fluids (CBGC1, CBGC2, CBGC3, CBGC4, CBGC5) were prepared by varying the weight percentages (wt.%) of EAs (5, 10, 15, 20, 25) with CO, and their thermo-physical properties were meticulously analyzed. Among these formulations, CBGC2 demonstrated superior lubrication performance, making it the most promising oil for further investigation. Subsequently, the effect of different NP was investigated by adding alumina (Al2O3), graphene (Gr) and multi walled carbon nanotubes (MWCNT) NPs in the CBGC2 solution in the ratio of 0.4, 0.8 and 1.2 in weight percent (wt.%) and the experimental results reveal substantial enhancements in thermophysical properties. Among various samples, the nanofluid containing 0.8 wt.% concentration of Al2O3 nanoparticles in CBGC2 exhibited the highest viscosity. Additionally, the thermal conductivity of the nanofluid enhanced by 24.82% when 1.2 wt.% of Gr nanoparticles added oil compared to CBGC2. Furthermore, in tribological tests, CBGC2 with 0.4% Al2O3 exhibited the lowest frictional force among the prepared cutting fluids. The contact angle reduced to a maximum extent by 11.14% for cutting fluids containing 1.2% alumina nanoparticles. These findings suggest that these innovative green cutting fluid formulations with nano-additives hold great potential for improving machining processes in various industrial applications towards sustainability
Boundary Condition Options for Carotid Bifurcation Analysis, Using Doppler Velocity Measurements
Get PDFThe Common Carotid Artery plays a vital role in supplying the brain, and its bifurcation is susceptible to vascular diseases. It is often analyzed using computational fluid dynamics (CFD) simulations, but it is challenging to prescribe boundary conditions that approach patient-specific flow conditions. We examined six boundary condition (BC) groups to determine the most accurate flow conditions aligning with available measured data. We conducted CFD simulations on a stenotic carotid bifurcation, using patient-specific Doppler ultrasound sonography velocity measurements at the inlet and both outlets. Three BC methods used defined inlet flow rate and either constant pressure (Basic), Windkessel model, or constant flow ratio (Murray) at the outlets. Three other methods were defined with flow rates at two boundaries and constant pressure at the third one. Defining two boundary flow rates shows the closest results to physiologically valid data. However, the difficult Doppler measurements on the outlet branches can inaccurately amplify velocity amplitudes and may detect a false flow direction. Therefore, cross-sectional corrections were implemented to fit the outlet and inlet flow rates, while keeping the measured velocity histories.Our results show that the Murray and Basic methods, while easily available, exclude carotid-specific flow conditions by disregarding downstream flow resistances. We conclude that a Windkessel-method can produce the most accurate results without forcing outflow conditions. However, usually unavailable measurements are necessary for its application. Simulations with outlet-defined volume flow can also produce physiologically valid solutions but require the application of cross-sectional geometry correction
Surface Anisotropy on 3D Printed Parts
Get PDFIt is well known that the surface quality obtained in additive manufacturing processes is highly variable. There are several reasons for this, of which the most prominent is the staircase effect, which results from the fact that 3D printing can be actually considered as a 2.5 machining process, as we build the part layer by layer. However, this staircase effect can be very different on surfaces that are arranged in different ways. By measuring the values that characterise the surfaces (Ra, Rz), however, we can observe that they are direction dependent, i.e. it does not matter how we measure them. This phenomenon is called surface anisotropy. It is clear that the surface roughness also has an effect on the tribological behaviour. In the case of a component where it is in contact with another component and relative displacement occurs between them, frictional properties may play a prominent role, which may thus also become direction dependent. Surface roughness also has a clear effect on fatigue properties. Consequently, for parts undergoing periodic dynamic stresses, it may be important to choose the right manufacturing orientation. The present study aims to demonstrate the extent of variation in surface roughness on different surfaces of a part produced by FDM. For this purpose, surface quality factors are investigated and evaluated on a self-designed model produced with given manufacturing parameters
Analysis of the Impact of the Effects of Modernisation of the Railway Line on the Quality of Travel on the Section Piła – Poznań
Get PDFThe article's purpose is to show the impact of the modernisation of the section Piła – Poznań of railway route No. 354 on the quality of travel. The detailed characteristics of the railway infrastructure in Poland and the elements included in it are presented. Modernisation of railway line No. 354 on the route Piła – Poznań was included in the Program of the Wielkopolska Regional Operational Program for 2014–2020. As a result, 134 km of track were replaced, translating into a reduced travel time. The modernisation allowed for the reconstruction of the traffic control system equipment. The entire railway line is controlled remotely from Poznań station.The punctuality level at Pila station when running trains between Pila and Poznań for November and December 2021 was 92.68%. The punctuality level at Poznań station when running trains from Piła to Poznań station for November and December 2021 was 89.61%. In December at Pila station, rolling stock breakdowns caused as much as 40% of all delays. 53.8% of respondents travelled most often, several times a year. According to the respondents, the comfort of travel has significantly increased, as well as punctuality. After the analysis, it was concluded that modernisation positively impacted the quality of travel
Szubjektív szakmai benyomások egy nemzetközi konferencia kapcsán – IFLA Midterm meeting Róma (2024. március 22–24.)
No full textThis short overview highlights selected topics from the rich program of the IFLA Midterm Meeting in Rome. The focus of the first day was on digital preservation and the second day was on Library and Information Science education and research theories. This event offered good opportunities for professional discussions among people from the academic world, library world, and schools.A szakmai beszámoló a teljesség igénye nélkül villant fel néhány, a szerző által válogatott témakört a Rómában megrendezett IFLA Midterm Meeting programjából. A rendezvény fő sarokpontjait az első napon a digitális megőrzés kérdései, a második napon a különféle könyvtár- és információtudományi képzési, kutatási, kutatásmódszertani kérdések jelentették. A konferencia gazdag eszmecserékre nyújtott lehetőséget az akadémiai világ képviselői, kutatói, a gyakorlati munkát végző könyvtárosok, illetve könyvtárostanárok között
