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Item type:Item, Access status: Open Access , Film Thickness and Friction of Textured Surfaces in Hydrodynamic Inclined and Parallel Gaps-An Experimental Study(MDPI, 2026-01-06) Šperka, Petr; Knotek, Jan; Omasta, Milan; Křupka, Ivan; Polach, Pavel; Hartl, MartinThis paper presents an experimental study on the influence of surface texturing on friction and film thickness in the hydrodynamic lubrication regime. Using a pin-on-disk tribometer equipped with light-induced fluorescence microscopy, simultaneous measurements were conducted on smooth and textured samples under parallel and inclined surface conditions. The circular faces of the pins were partially or fully covered by circular laser-machined textures consisting of dimples with depths of 5 or 10 mu m, diameters of 50 or 100 mu m, and coverage density of 20%. The results demonstrate that while texturing significantly reduces friction and increases film thickness in parallel gaps, with partial inlet coverage being the most effective, its impact is minimal in inclined wedge gaps. The study further reveals that the global geometric wedge dominates over texture effects in inclined contacts and that in-texture cavitation, prevalent in parallel conditions, is suppressed by surface inclination. Three distinct contributions of the textures were discussed: a global hydrodynamic effect, a local hydrodynamic effect, and the influence of surface non-flatness (waviness). The findings suggest that texturing is primarily beneficial for acting as a pseudo-wedge or as surface roughness in contacts where a physical wedge is absent.Item type:Item, Access status: Metadata only , Experimental Study of the Effect of Surface Texture in Sliding Contacts Using Infrared Thermography(MDPI, 2026-01-31) Omasta, Milan; Knoth, Tomas; Šperka, Petr; Hajzman, Michal; Křupka, Ivan; Polach, Pavel; Hartl, MartinThis study investigates the influence of surface texturing on temperature distribution in lubricated sliding contacts using infrared thermography. The work addresses the broader challenge of understanding thermal effects in conformal hydrodynamic contacts, where localized heating and viscosity variations can significantly affect tribological performance. A pin-on-disc configuration was employed, featuring steel pins with laser-etched micro-dimples that slid against a sapphire disc, allowing for thermal imaging of the contact zone. A dual-bandpass filter infrared thermography technique was developed and rigorously calibrated to distinguish between the temperatures of the steel surface and the lubricant film. Friction measurements and laser-induced fluorescence were used in parallel to assess contact conditions and the behavior of the lubricant film. The results show that surface textures can alter local frictional heating and contribute to non-uniform temperature distributions, particularly in parallel contact geometries. Lubricant temperature was consistently higher than the surface temperature, highlighting the role of shear heating within the fluid film. However, within the tested parameter range, no unambiguous viscosity-wedge signature was identified beyond the dominant temperature-driven viscosity reduction captured by the in situ correction. The method provides a novel means of experimentally resolving temperature fields in sliding textured contacts, offering a valuable foundation for validating thermo-hydrodynamic models in lubricated tribological systems.Item type:Item, Access status: Open Access , UWB Indoor Localization Based on XGBoost NLOS Identification and DS-TWR Ranging(Radioengineering Society, 2026-06) Xu, X. Yao Z.; Liu, G.Indoor environments present significant challenges for ultra-wideband (UWB) localization due to ranging errors and non-line-of-sight (NLOS) propagation. This paper proposes a robust UWB indoor localization framework that integrates double-sided two-way ranging (DS-TWR), XGBoost-based NLOS identification, residual-weighted localization, and Kalman filter (KF). The main contribution of this work is the unified use of NLOS identification in both ranging correction and localization fusion, significantly improving localization accuracy in complex environments. Experimental results demonstrate improvements in ranging accuracy of up to 53.7% and 47.22% under human-body and wooden-board occlusions. In dynamic experiments, the proposed method outperforms conventional UWB localization, KF, and weighted least squares methods with positioning accuracy improvements of 38.64%, 28.95%, and 12.9%, respectively. These results confirm the framework’s effectiveness in mitigating NLOS impact and enhancing UWB localization robustness.Item type:Item, Access status: Open Access , Mid-Air Hand Rehabilitation Evaluation and Virtual Training System(Radioengineering Society, 2026-06) Zhou, R.; Lai, P.; Chen, L.; Hu, Z.; Qian, L.This paper presents the design of a mid-air hand rehabilitation evaluation and virtual training system based on Leap Motion and gesture recognition algorithms. The system aims to provide a scientifically-grounded and accessible home-based rehabilitation solution for patients with hand injuries. It employs a spatio-temporal attention-enhanced multi-scale residual graph convolutional network algorithm for gesture recognition. Following this, specific joint angles are calculated and 14 representative gesture scores are derived. Weights are assigned to each scoring item via ridge regression to achieve a quantitative assessment. The rehabilitation training module comprises two modes: interactive turn-based games and music rhythm games, designed to train hand movement and dexterity. The system was subsequently tested to evaluate the performance of both the assessment function and the two training games. Results show an average gesture recognition accuracy of 94.86%. Furthermore, the reliability scores for both training games exceeded 90%. These findings demonstrate that the system achieves good accuracy in gesture recognition and effective assessment of hand rehabilitation progress.Item type:Item, Access status: Open Access , DSSZ-SM: A Simplified Chirp Coding Scheme with Inherent Clock Synchronization(Radioengineering Society, 2026-06) Kirasamuthranon, L.; Koseeyaporn, J.; Wardkein, P.This study proposes a novel double-slope chirp symbol, termed double–slope start zero stop minimum (DSSZ–SM), for efficient data communication. Unlike conventional chirp coding, which often involves complex generation and synchronization, the DSSZ–SM provides a simpler structure with inherent clock synchronization using a PWM-based generator. System performance is evaluated through analysis and simulations over additive white Gaussian noise (AWGN) and Rayleigh fading channels. Two asynchronous decoding methods, with and without an integrator, are compared. Results show that the non-integrator approach achieves lower error rates under both channel conditions. The proposed DSSZ–SM offers a simplified and robust alternative for efficient data communication.