Discrete-Time Attitude Tracking Synchronization for Swarms of Spacecraft Exploiting Interference

The attitude tracking synchronization control of an orbit-predetermined leader–follower spacecraft swarm for the space moving target is discussed in this paper. The information exchange between all spacecraft is assumed to be discrete in time and on the undirected connected graph. Moreover, due to the demand for saving communication resources, wireless interference has been utilized, which allows all the neighbors of a spacecraft to access the same channel frequency spectrum simultaneously. Then the backstepping control algorithm is designed to let the spacecraft (β,A)-practically stably synchronize their states and track a time-varying trajectory in the presence of unknown fading channels. Finally, simulation is provided to verify that using the proposed control scheme, the attitude tracking synchronization can be achieved with high precision

Co-Based Catalysts Supported on Ceria with Different Shape Structures for Hydrodeoxygenation of Guaiacol

CeO2 with three different morphologies of nanorods (CeO2-r), particles (CeO2-p), and cubes (CeO2-c) was prepared, and the guaiacol hydrodeoxygenation over their corresponding Co-based catalysts was performed at 160–220 °C, 2 MPa, a H2 flow rate of 80 mL/min, and a weight hourly space velocity of 0.7 h–1. Compared with Co/CeO2-p and Co/CeO2-c, Co/CeO2-r has smaller Co particle sizes, a higher Brunauer–Emmett–Teller surface area, and larger amount of Co active centers, oxygen vacancies, and weak acid sites. These better physicochemical properties for Co/CeO2-r provide more Co active sites for guaiacol hydrodeoxygenation, favor the adsorption and activation of guaiacol, and contribute to the cleavage of C–O. Therefore, Co/CeO2-r presents a maximum guaiacol conversion of 97.1% and the highest yield of cyclohexanol of 91.7% among these catalysts. The result shows that the shape structure of CeO2 has an important influence on the guaiacol hydrodeoxygenation performance over its corresponding catalysts

Formic Acid‐Assisted Selective Hydrogenolysis of 5‐Hydroxymethylfurfural to 2,5‐Dimethylfuran over Bifunctional Pd Nanoparticles Supported on N‐Doped Mesoporous Carbon

Biomass‐derived 5‐hydroxymethylfurfural (HMF) is regarded as one of the most promising platform chemicals to produce 2,5‐dimethylfuran (DMF) as a potential liquid transportation fuel. Pd nanoparticles supported on N‐containing and N‐free mesoporous carbon materials were prepared, characterized, and applied in the hydrogenolysis of HMF to DMF under mild reaction conditions. Quantitative conversion of HMF to DMF was achieved in the presence of formic acid (FA) and H$_2$ over Pd/NMC within 2 h. The reaction mechanism, especially the multiple roles of FA, was explored through a detailed comparative study by varying hydrogen source, additive, and substrate as well as by applying in situ ATR‐IR spectroscopy. The major role of FA is to shift the dominant reaction pathway from the hydrogenation of the aldehyde group to the hydrogenolysis of the hydroxymethyl group via the protonation by FA at the C‐OH group, lowering the activation barrier of the C−O bond cleavage and thus significantly enhancing the reaction rate. XPS results and DFT calculations revealed that Pd$^{2+}$ species interacting with pyridine‐like N atoms significantly enhance the selective hydrogenolysis of the C−OH bond in the presence of FA due to their high ability for the activation of FA and the stabilization of H$^−$