Gyan Ganga Institute of Technology and Sciences

This study presents a model predictive path integral (MPPI) method capable of conducting high-frequency real-time model predictive control (MPC) for robot manipulators. Real-time MPC-based manipulation holds significant potential for controlling an end-effector precisely and reactively while satisfying various constraints in dynamic environments. However, the optimization under a complex robot model and various constraints imposes a heavy computational burden, hindering the realization of high-frequency updates. To address this challenge, we propose a single-instance sampling-based MPPI algorithm and dynamic time horizon to significantly reduce the computational burden while enhancing control performance. The performance and efficacy of the proposed method are verified through experiments conducted on a 7-degree-of-freedom robotic arm, along with comparative simulations and analysis.

Lower limb exoskeletons assist users by supporting joint movements. Since joint motion patterns vary depending on how the user moves, accurately recognizing the type of movement (locomotion mode) is crucial for controlling the exoskeleton and ensuring user safety. Inspired by how humans use multiple types of sensory information to control movement, we developed a multi-modal locomotion mode recognition (LMR) system that uses both mechanical and visual sensor data to identify locomotion modes. Our approach utilizes two fusion methods: intermediate fusion, which combines the data in the form of features, and late fusion, which integrates the sensor data by averaging the recognition results from each sensor. By fusing these two different modalities, the prediction accuracy improved by an average of 11.7% with the test data. Through comparisons with uni-modal LMR systems that rely on a single type of sensor data for locomotion mode recognition, we found that the improved performance of the multi-modal LMR system is due to the visual information's ability to generalize different gait patterns across users and the mechanical sensor data's consistency within the same classes.

This study demonstrated that metal-carbon composites (Me-N-C; Me = Mn, Fe, Co, Ni, and Cu) featuring sulfidated metal nanoparticles encapsulated within an N-doped carbon matrix activated both persulfate and O3, albeit through distinct mechanisms. The carbon phase, exhibiting enhanced electrical conductivity due to the presence of internal metal cores, facilitated non-radical persulfate activation. In contrast, the metallic constituent predominantly converted O3 to hydroxyl radical (center dot OH). This oxidant-dependent shift in the principal catalytic site (or degradation pathway) was substantiated by a mechanistic examination of oxidant activation by Ni-N-C that varied in structural characteristics and chemical compositions. The persulfate activation capability of Ni-N-C rose proportionally with the content of graphitic-N as the key species in the non-radical activation pathway. Conversely, center dot OH yield from O3 correlated strongly with the degree of Ni sulfidation, suggesting that sulfidated Ni functioned as the catalytic center for O3 activation. The active-site switching was further supported by the impact of H2-assisted pyrolysis, which suppressed Ni sulfidation while enriching graphitic-N, thereby enhancing persulfate activation but kinetically retarding O3-to-center dot OH conversion. UV irradiation, preventing surface organic accumulation, and thermal sulfidation, enriching metal sulfide content, effectively regenerated Ni-N-C by targeting the respective catalytic centers for persulfate and O3 activation. DFT calculations indicated that Ni3S2 displayed a preferential tendency to dissociatively adsorb and subsequently activate O3, whereas carbonencapsulated Ni promoted non-radical persulfate activation at the carbon interface. The identification of oxidant-specific catalytic sites provided a pivotal design rationale for developing metal-carbon composites as versatile catalysts for oxidant activation.

Solution-processed nanocrystalline oxide semiconductors offer great potential for next-generation displays and sensors owing to their excellent large-area uniformity, compatibility with low-cost fabrication techniques, and superior electrical performance compared to the amorphous phase. However, the typical trade-off between high electron mobility and bias stability of oxide semiconductor-based thin-film transistors (TFTs) remains a key obstacle to developing high-performance devices for practical applications. Herein, 355 nm fiber laser irradiation is introduced as an effective strategy to simultaneously enhance mobility and bias stability in solution-processed indium gallium oxide (IGO) thin films. The composition of IGO was optimized at 7.5% Ga incorporation for efficient 355 nm absorption, facile crystallization, and suppression of oxygen vacancies. The fiber laser post-treatment on a 7.5% Ga incorporated IGO film induced rapid localized heating, which promoted crystallization of the semiconductor layer within a short timescale and reduced structural disorder. Consequently, the optimized device, irradiated at 50 mJ cm-2, exhibits a high mobility of 36.74 cm2 V-1 s-1 with a threshold voltage close to 0 V, along with excellent electrical stability with threshold voltage shifts of 0.04 V and -1.9 V at a positive and negative bias stress of 2 MV cm-1 for 10 000 s, respectively. These results demonstrate that low-cost fiber laser-assisted post-treatment effectively addresses the mobility-stability trade-off, providing a viable pathway toward high-performance solution-processed oxide semiconductors for next-generation electronic applications.

Fluorinated halide solid electrolytes (FHSEs) enable integration with high-voltage layered oxides in all-solid-state sodium-ion batteries (ASSSIBs). Here, we demonstrate high-voltage ASSSIBs by pairing a fluorine-substituted UCl3-type chloride solid electrolyte, Na0.6Ta0.2La0.8Cl3.7F0.3, with a P2-type Na0.8Li0.1Ni0.2Mn0.7O2 cathode. The ASSSIB achieves reversible oxygen redox up to 4.6 V and delivers 132 mAh g-1 with long-term cycling stability, surpassing the performance of liquid electrolytes and nonfluorinated halide counterparts. Electrochemical and structural analyses reveal that, in liquid-electrolyte cells, oxygen redox above 4.2 V becomes irreversible due to solvent oxidation and surface-layer formation, while phase transitions further degrade structural reversibility. In contrast, the FHSE preserves the P2 framework and stabilizes oxygen-redox activity, enabling higher capacity and long-term cycling stability. Supported by integrated theoretical calculations, electrochemical analyses, and advanced characterizations, this work presents a viable strategy for advancing high-voltage ASSSIBs. Overall, FHSEs enable stabilized oxygen redox above 4.2 V and realize durable, high-energy ASSSIBs.