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Spin-wave microscale RF delay lines for mid- and high-frequency 5G band
(2025-10-14) Davídková, Kristýna; Levchenko, Khrystyna O.; Serha, Rostyslav O.; Bruckner, Florian; Lindner, Morris; Dubs, Carsten; Urbánek, Michal; Suess, Dieter; Wang, Qi; Verba, Roman V.; Chumak, Andrii V.
Delay lines (DL) are crucial components in communication systems, providing the required time delays for signal timing, synchronization, and processing. DLs providing nanosecond-scale delays are conventionally based on acoustic waves; however, they cannot operate conveniently in a high-frequency range (EU 5G high-band 24.25-27.5 GHz) required by a modern generation of 5G communication technologies to speed up data transfer. The proposed solution is to use DL based on spin-wave (SW) transmission, as SW devices allow for operation at high-frequency ranges and can be scaled down to a few m 2 . In this study, we investigate SW-based DL at the microscale at the frequency ranges of 4, 9, and 25 GHz. The DL is based on SW transmission between a pair of 250 nm wide microwave coplanar waveguide transducers, each with a footprint of 2.25 × 100 m 2 , and fabricated with varying mutual distances on a 97 nm thin yttrium iron garnet film. DLs are tested for in-plane SW modes (Damon-Eshbach and backward volume), and depending on the parameters, the extracted delay times are in the range of 6-165 ns. Furthermore, the insertion losses are extracted and compared to other DL concepts. Time-gating analysis of the measured transmission is performed, providing a detailed discussion of individual signal contributions to the measured spectra. Additionally, analytical theory is employed to compare the experimental delay times with analytical calculations and to predict how to adjust the device parameters to obtain variable time delays.
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Enhanced corrosion resistance of 2024 aluminum alloys with Cr2O3 thin layers by Atomic Layer Deposition
(2025-11-01) Mercier, Dimitri; Zazpe Mendioroz, Raúl; Wang, Xiaozhen; Michaux, Maria Celina; Rodriguez Pereira, Jhonatan; Zanna, Sandrine; Seyeux, Antoine; Macák, Jan; Marcus, Philippe
This research explores the use of chromium oxide (Cr2O3) thin layers grown by Atomic Layer Deposition (ALD) as protective coating to enhance the corrosion resistance of 2024 aluminum alloys. In order to obtain sufficiently dense and uniform Cr2O3 layers, the ALD process was tailored in terms of alloy surface pretreatment before the main Cr2O3 ALD process. The corrosion resistance of both Cr2O3 coated and non-coated aluminum alloys was evaluated in a corrosive 0.1 M KOH environment using in situ optical microscopy and ex situ surface analysis techniques, including X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and a neutral environment containing chlorides. Findings revealed that the Cr2O3-coated samples exhibited significantly reduced reactivity, highlighting the excellent corrosion protection provided by the Cr2O3 thin films. Although surface analysis revealed the presence of submicron defects within the Cr2O3 layer, which could act as corrosion initiation sites, the occurrence of these defects was mitigated with increasing Cr2O3 layer thickness. Additionally, after the corrosion test, an enrichment of copper and aluminum oxides at the layer surface was observed, suggesting preferential attack at intermetallic phases in corrosive environment.
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Recent advances of nanozyme-enhanced electrochemical biosensors for antibiotic detection in foods: Trends, opportunities, and challenges
(2025-12-01) Garehbaghi, Sanam; Gharibzahedi, Seyed Mohammad Taghi; Altintas, Zeynep
Nanozyme (NZ)-enhanced electrochemical (EC) biosensors have significantly advanced as a result of the growing need for quick, sensitive, and on-site detection of antibiotic residues in food. This study thoroughly reviews the latest developments in NZ-based EC biosensors for the detection of antibiotics in food matrices, including conventional EC, electrochemiluminescence (ECL), photoelectrochemical (PEC), and dual-mode colorimetric-electrochemical (CM-EC) platforms. NZ-based biosensors have emerged as viable substitutes for traditional chromatographic techniques (such as HPLC and LC-MS/MS), which are still the gold standard for sensitivity and multi-residue analysis owing to their high cost, labor-intensive procedures, and lack of portability. Because of their enzyme-mimicking catalytic activity, NZs improve signal amplification, allowing for molecularly imprinted polymer (MIP) or aptamer recognition for ultrasensitive detection with low limits of detection and high specificity. Dual-mode CM-EC devices combine visual simplicity with quantitative precision, while ECL and PEC sensors further increase sensitivity by integrating light-driven processes and catalytic precipitation. Despite their advantages, challenges such as matrix effects, synthesis scalability, and cross-reactivity hinder widespread adoption. Miniaturization, smartphone integration, and increased uses in food safety monitoring are potential future developments.
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Monotonicity character of convex combinations of two sequences generated by the square of the cube root function
(2025-10-15) Stevic, Stevo; Iričanin, Bratislav D.; Kosmala, Witold; Šmarda, Zdeněk
There is a natural connection between the finite sums of the reciprocals of the squares of the cube roots of positive natural numbers and two definite integrals. By using the differences between the sums and the integrals are formed in a natural way two sequences of real numbers converging to the same finite limit. We completely determine the monotonicity character of the sequences which are obtained by convex combinations of the two sequences, in an elegant way. We also present an interesting result about monotonicity character of a real function on the interval , which is used in the proof of the main result. The results are important for solving difference equations.
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The Potential of Using Birotor Machines in Modern Transport Means
(2025-10-29) Fomin, Oleksij; Chubykalo, Mikhaylo; Lohvinenko, Oleksandr; Píštěk, Václav; Kučera, Pavel
The transport sector requires compact, reliable, and energy-efficient power units for modernization of road, rail, maritime, and aerial systems. Conventional piston and rotary machines often face limitations related to vibration, sealing losses, and manufacturing complexity. This study investigates birotor machines (BM), a class of positive-displacement devices combining synchronized rotation of the rotor and housing. This configuration ensures smooth kinematics, near-complete dynamic balance, and simplified design. The working principle enables continuous volumetric transformation with reduced friction and leakage, enhancing efficiency and durability. Using generalized mathematical models (GMM) developed through statistical experimental design, optimal geometric parameters were determined with a root-mean-square error below 3%. A prototype birotor compressor (BC) designed for subway rolling stock achieved equivalent output performance (0.43 m3/min at 0.8 MPa) with 82% efficiency and a mass reduction from 130 kg to 32 kg. Comparative simulations and preliminary testing of BM-based internal combustion engines (BRICE) demonstrated 3–4 times smaller and lighter units with improved reliability and environmental characteristics. The results confirm that BM technology provides a feasible and manufacturable alternative to conventional designs, suitable for integration into next-generation transport and unmanned vehicle systems.