An adaptive optical buffer is proposed for contention resolution in optical packet switching (OPS) networks by combining spectral-amplitude coding (SAC) with polarization-division multiplexing (PDM) for optical labeling. The buffer dynamically switches between two traffic-dependent labeling modes on a shared hardware platform. Under heavy traffic, on–off keying (OOK) labeling uses the two polarization states to provide an additional label dimension, thereby doubling the effective buffer capacity. Under light traffic, two-code keying (TCK) labeling maps distinct label bit states onto the polarization dimension, improving label recognition robustness and reducing decoder noise. A packet-loss probability (PLP) model is developed to evaluate both buffer blocking and label misrecognition. The resulting switching threshold provides a quantitative criterion for selecting the preferred operating mode. Numerical results show that the adaptive scheme operates in the lower-loss mode and outperforms conventional SAC configurations over the considered load range. The analysis shows how the proposed buffer balances capacity and label recognition robustness across regimes dominated by buffer blocking or decoder noise.
Visually impaired users face significant challenges in navigating complex indoor environments due to limited spatial awareness and lack of real-time semantic guidance. This paper proposes a multimodal navigation system integrating environmental perception with vision-language models (VLMs). It provides context-aware and explainable guidance without requiring additional infrastructure. The proposed system combines RTAB-Map for localization, YOLO-World for open-vocabulary object detection, and a lightweight language model for semantic reasoning and natural language interaction. To evaluate our system, experiments are conducted using the RePOPE benchmark to assess hallucination in vision-language understanding. Real-world indoor navigation experiments are also performed. The results show that integrating perception with language-based reasoning improves precision by up to 2.29% and consistently enhances F1-score compared to baseline VLM approaches. Real-world experiments further demonstrate reliable navigation performance, including multi-floor path planning and obstacle-aware guidance. Hence, the proposed system effectively enhances spatial understanding and reduces hallucination, providing a practical and scalable solution for assistive navigation.
This study aims to investigate the influence of parasitic capacitances within half-bridge SiC power metal oxide semiconductor field effect transistor (MOSFET) modules, including input capacitance (Ciss), output capacitance (Coss), and reverse transfer capacitance (Crss), on their switching transients and switching losses during dynamic switching. A secondary objective is to assess the impact of parasitic capacitances on power loss and thermal performance in a single-phase SiC MOSFET inverter operating in an H-bridge configuration that employs two half-bridge SiC power MOSFET modules identical to the one described above. To accurately capture the switching transients, switching losses, and parasitic effects of the SiC power module during dynamic transients and inverter operating under sinusoidal pulse-width modulation (SPWM) in single-phase open-loop mode, an electromagnetic-circuit modeling (EMCM) framework is developed. This approach integrates an electromagnetic model, an equivalent circuit model, and a SiC MOSFET characteristic model. The validity of the proposed integrated modeling framework is verified by comparison with the measurement results obtained from double-pulse testing (DPT) and thermal resistance experiments. Ultimately, using the developed integrated modeling framework, a guideline for improving power loss and thermal behavior of the power inverter under various device and system conditions is formulated through parametric analysis. The findings demonstrate that parasitic capacitances significantly affect switching waveforms and loss, and also influence the thermal performance of the system, with Crss showing the most dominant impact.
The stabilization of metastable amorphous phases is a crucial-materials processing strategy for minimizing resistance drift and improving the endurance and reliability of Phase Change (PcRAM) and Resistive memory (ReRAM) devices. As-deposited amorphous metal chalcogenide thin films exhibit high electrical resistance, which enables their operation as OFF-state in phase change memory device applications. However, they exhibit a metastable nature, which is detrimental to memory devices due to resistance drift over time, ultimately limiting the device's endurance and reliability. In this work, we demonstrate that low-energy Ar(+) ion irradiation can be used as a controlled method to induce atomic rearrangement and densification. This process effectively stabilizes the amorphous network of Se77.5-XTe20Sn2.5AgX (X = 2.5, and 7.5) thin films. The influence of irradiation on the structural, morphological, optical, and electrical properties is systematically investigated to confirm the evolution of amorphous stabilization. The comprehensive analysis confirms that Ar(+) ion irradiation has effectively reduced the metastability and also has improved the structural uniformity, leading to enhanced electrical stability. Our results and findings demonstrate that low-energy ion treatment is a promising strategy for improving the functional reliability of Se-Te-Sn-Ag (STSA) thin films for memory, optoelectronic, and thermoelectric applications.
This study numerically explores hydrogen production via steam methane reforming in a sorption-enhanced membrane reactor (SE-MR) equipped with a palladium-ruthenium (Pd-Ru) membrane. The SE-MR integrates two key enhancement mechanisms: CO2 capture using a calcium oxide (CaO) sorbent and selective hydrogen removal through a dense metal membrane, thereby improving methane conversion efficiency and hydrogen purity simultaneously. The dynamic sorption process begins at the reactor inlet and gradually propagates downstream and radially from the membrane to the outer wall. It is observed that CO2 produced near the membrane is quickly absorbed; however, localized saturation in this region leads to an early and mild CO2 breakthrough, which becomes less pronounced at higher weight hourly space velocities (WHSV). Similarly, the effective duration of CO2 uptake diminishes with increasing sweep gas flow rate due to accelerated sorbent saturation. Quantitative results demonstrate that the SE-MR significantly enhances performance, achieving a 19.04 % increase in CH4 conversion and a 28.91 % improvement in hydrogen permeation rate compared to a conventional membrane reactor (MR) without CO2 capture. As a result, the dual-enhanced mechanism in SE-MR intensifies the H2 yield rate by 20.76 % compared to MR. These findings confirm that the synergistic integration of in-situ CO2 sorption and membrane separation can significantly enhance hydrogen yield and purity, providing a highly efficient and compact pathway for blue hydrogen production in advanced energy systems.
