Diesel fuel stability can be considered from many points of view, of which the two considered most important are stability in contact with the environment and internal stability. Fuel stability in touch with the environment is often defined as oxidation stability, of which measurement procedures are well developed. The presented paper shows that fuel’s internal stability can also be important. The internal stability of diesel fuel with the local use of thermal and ultraviolet radiation (UV) as degradation factors and fluorescence signals as a probe is presented in this paper. We show that the internal degradation of fuel with temperature use differs from that with UV and simultaneous both factors use. Our study shows that using temperature as a degradation factor introduces significant fluorescence fading. Moreover, the fluorescence signal restores significantly later than the sample stabilizes at room temperature. The novelty proposed based on examination is hybrid degradation and an examination cycle that enables the simultaneous use of degradation factors and fluorescence reading. For this purpose, a dedicated measurement setup of signal control and processing was constructed and programmed. The measurement procedure of the data series for specific wavelength enables calculation of signal shifts that allow the internal stability classification of diesel fuel samples in less than 30 min with the cost of a single disposable capillary probe and one polymer plug. Premium and regular fuel examination results show that internal fuel stability can be related to polycyclic aromatic hydrocarbons (PAH) concentrations and can be modified with dedicated additives.
In this paper, the technology for fabricating NiFe/Cu/NiFe layered structures by magnetron sputtering is presented. Two series of samples were fabricated on a glass substrate with a layered structure, where the individual layers were 30 nm NiFe, 5 nm Cu, and finally NiFe with a thickness of 30 nm. The series differed in the type of technology mask used. A constant magnetic field was applied to the substrate during the sputtering of the ferromagnetic layers. Measurements of the DC resistance of the obtained structures in the constant magnetic field of neodymium magnet packs with a constant magnetic field of about 0.5 T magnetic induction have been carried out. Comparison of the two series allows us to conclude the greater validity of using masks in the form of Kapton tape. The obtained results seem to confirm the occurrence of phenomena referred to as the giant magnetoresistance effect.
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