The difference in psychological behavior when drivers cross the road has a certain impact on the efficiency of crossing the road. On the basis of analyzing the subjective and objective factors of drivers, the entropy change model of green light time is established and verified. The model can simply judge the time when the driver faces different traffic lights, so as to effectively calculate the drivers driving speed, analyze the traffic situation, and improve the traffic efficiency.
Compared to the acidic hydrogen evolution reaction (HER), the sluggish reaction rate in an alkaline electrolyte makes it a priority to develop highly efficient and cost-effective catalysts. Incorporation of Pt with transition metals to form alloy nanocrystals with different structures and atomic distributions has been reported as a promising approach to enhance HER activity and improve Pt utilization. However, whether the structural ordering of the Pt-based bimetallic alloy affects the HER activity still remains unknown. Here, we synthesized PtNi/C nanoparticles through a modified coprecipitation method and obtained their ordered and disordered phases at different annealing temperatures in a reducing atmosphere. It is contrary to our expectation that the disordered PtNi/C exhibited a superior activity toward the HER in alkaline media compared with the ordered PtNi/C. To understand this interesting phenomenon, a systematic study combining X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) was conducted. In addition, we studied the mechanism of the HER in an alkaline electrolyte based on newly constructed models. The density functional theory (DFT) calculation demonstrated that the unexpected activity change may be attributed to the synergistic effect between the formation of Ni/Pt–OH bonds and the increased degree of disorder of Pt and Ni atoms on their surface.
For silicon-based devices using dielectric oxides doped with rare earth ions, their electroluminescence (EL) performance relies on the sufficient carrier injection. In this work, the atomic Ga2O3 layers are inserted within the Er-doped GeO2 nanofilms fabricated by atomic layer deposition (ALD). Both Ga(CH3)3 and Ga(C2H5)3 could realize the ALD growth of Ga2O3 onto the as-deposited GeO2 nanofilm with unaffected deposition rates. The interfacial defects introduced by atomic Ga2O3 layers decrease the threshold voltage while increasing the tolerable injection current of the EL devices; the 1530 nm emissions from the 600 °C-annealed Ga2O3/GeO2:Er nanolaminate devices achieve the optical power density of 16.2 mW/cm2, with the excitation efficiency increased to 12.5%. Moreover, the interface modification by atomic Ga2O3 layers significantly prolongs the operation time of these prototype devices, reaching 5.21 × 104 s for the optimal one. High-temperature annealing above 800 °C results in the decomposition of GeO2 and leaves reticular porous nanofilms. The conduction mode within these amorphous Ga2O3/GeO2:Er nanolaminates conforms to the trap-assisted tunneling mechanism, with the depths of defect states lowered by the interfacial Ga2O3 layers. These Ga2O3/GeO2:Er nanolaminates with improved EL performance demonstrate new potential in the utilization of ALD GeO2 nanofilms in silicon-compatible optoelectronics.
Abstract Er 3+ ‐doped polycrystalline MgAl 2 O 4 (MAO:Er) spinel nanofilms are deposited via atomic layer deposition, and the metal‐oxide–semiconductor light emitting devices are fabricated. The crystallinity and morphology of the MAO:Er nanofilms are explored by modifying the annealing temperatures, Al 2 O 3 /MgO ratios and Er 2 O 3 dopant cycles. The similar electroluminescence (EL) emissions peaking at 1530 nm indicates the identical crystal field environment for the doped Er 3+ ions. The concentration quenching is verified to occurs via the energy transfer among the neighboring Er 3+ ions. The optimal device (800 °C‐annealed, Al 2 O 3 /MgO ratio close to stoichiometry, Er 3+ : 1.85 mol%) yields the highest external quantum efficiency of 28%, the power efficiency of 0.32% and the optical power density of 14.62 mW cm −2 . The smooth MAO:Er spinel nanofilms with the low refractive index and high resistance ensure the highly efficient light extraction and the generation of energetic electrons for the impact excitation of Er 3+ ions. The trap‐assisted tunneling under operation electric field dominates the conduction mechanism for the EL emissions. The estimated decay lifetime of 1154.4 µs and a large‐stimulated emission cross‐section in the order of 10 −15 –10 −14 cm 2 are revealed from the EL emissions. Intense near‐infrared emissions from these Si‐based MAO:Er devices have great potential in the optoelectronic applications.
Compared to the acidic hydrogen evolution reaction (HER), the sluggish reaction rate in an alkaline electrolyte makes it a priority to develop highly efficient and cost-effective catalysts. Incorporation of Pt with transition metals to form alloy nanocrystals with different structures and atomic distributions has been reported as a promising approach to enhance HER activity and improve Pt utilization. However, whether the structural ordering of the Pt-based bimetallic alloy affects the HER activity still remains unknown. Here, we synthesized PtNi/C nanoparticles through a modified coprecipitation method and obtained their ordered and disordered phases at different annealing temperatures in a reducing atmosphere. It is contrary to our expectation that the disordered PtNi/C exhibited a superior activity toward the HER in alkaline media compared with the ordered PtNi/C. To understand this interesting phenomenon, a systematic study combining X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) was conducted. In addition, we studied the mechanism of the HER in an alkaline electrolyte based on newly constructed models. The density functional theory (DFT) calculation demonstrated that the unexpected activity change may be attributed to the synergistic effect between the formation of Ni/Pt–OH bonds and the increased degree of disorder of Pt and Ni atoms on their surface.
Abstract Carbon fiber‐reinforced cyanate ester resin matrix composites (CF/CE) are widely used in aerospace for their high‐temperature resistance and wave‐absorbing properties. However, CF/CE is prone to interlaminar delamination during the curing molding process or practical applications due to the brittleness of CE resin. In this study, we use polyether sulfone (PES) as a toughening layer through the inter‐tow toughening method to prepare PES inter‐tow toughened CF/CE (CF/CE‐P) and to investigate their thermal, mechanical, and microscopic morphology. We find that CF/CE‐P has a higher glass transition temperature ( T g ) and a lower coefficient of thermal expansion (CTE) than those of CF/CE composites. The flexural strength, flexural modulus, interlaminar shear strength (ILSS), and impact toughness of CF/CE‐P with 15 wt% PES is increased by 34%, 15%, 34%, and 45%, respectively, compared to CF/CE. In addition, the mode I interlaminar fracture toughness ( G IC ) of CF/CE‐P with 15 wt% PES is 1.86 times that of CF/CE. Highlights The inter‐tow toughening technique on a three‐dimensional scale is proposed. Model I interlaminar fracture toughness increased by 86% after inter‐tow toughness modification carbon fiber‐reinforced cyanate ester resin matrix composites. The composite material exhibits improved toughness and thermal performance. The prepreg preparation process is suitable for continuous industrial production.
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