Fuels should behave appropriately in all sections of the engine system: the engine, fuel delivery system, and tank. Fuel quality can be linked to the following three crucial areas: performance, fitness for current use, and stability. Classical methods of diesel fuel examination mostly rely on the absolute value measurement of one specific parameter while stabilizing outside conditions. In contrast, multiparametric methods depend on simultaneously measuring a set of parameters. Therefore, multiparametric methods open the possibility of intriguing new examinations and classifications of diesel fuel quality while raising specific issues relating to the instrumentation and construction of sensing devices. This paper presents a review, based on the published literature and the authors’ research, of the current state-of-the-art multiparametric methods for rapid diesel fuel quality classification and related instrumentation, systematizing the various types of methods from the point of view of the principles of their operation. The main conclusion is that different measuring procedures use similar methods of data processing. Moreover, the heavy, costly, and complex devices that enable standard examinations can be converted to simpler devices in the future, whose cost of use is significantly lower. However, to achieve this, progress in electronic devices is required.

Steel automotive wheel rims are subject to wear and tear, down to the end of their service life. Manufacturers use standard destructive tests to determine the probable lifetime of the car wheel rim. With this approach, to predict the remaining use time, it is necessary to know the initial parameters of the wheel rim, actual mileage, and its use characteristics, which is difficult information to obtain in the real world. Moreover, this work shows that a vehicle’s technical condition can affect the rim’s remaining service time. This work describes a new method of precise binary identification of the technical condition of steel car wheel rims using the dispersion of damping factors which result from experimental modal analysis. This work also proposes a new method of indicating the approaching end of wheel rim service life with limited parameters: run-out, average of damping factors, and dispersion of damping factors. The proposed procedure requires two sequential examinations of the rim in standard periods related to the average annual mileage of the vehicle. On this basis, it is possible to indicate the approaching end of the life of the steel rims about 10,000 km in advance.

This work presents the system-level design, fabrication, and experimental validation of a 1-bit reconfigurable reflectarray with a $12\times 12$ aperture operating at 15 GHz in the Ku-band. Each unit cell consists of a circular microstrip patch with four symmetrically arranged PIN diodes that are driven collectively to realize two reflection states with an approximately 180° phase difference near the operating frequency. The fourfold-symmetric unit cell exhibits similar reflection characteristics for x- and y-polarized incidence. The complete prototype combines four reusable $6\times 6$ subarrays, a modular bias network, and an MCU-based controller that independently addresses all 144 unit cells. Measurements demonstrate beam steering from $-{50}^{\circ }$ to $+{50}^{\circ }$, a maximum measured gain of 17.9 dBi, an aperture efficiency of 17.8%, a cross-polarized level below $-25$ dB, and a 7.9% 1-dB gain bandwidth. The demonstrated combination of wide-angle beam steering, similar unit-cell characteristics for x- and y-polarized incidence, low cross-polarization, and reusable subarray construction provides a practical and scalable hardware approach for Ku-band wireless links, satellite communications, and radar systems.