Ammonia (NH3) is a promising green hydrogen carrier, and its synthesis under mild, distributed conditions has attracted increasing attention. Non-thermal plasma provides a potential route for ammonia synthesis by enabling nitrogen activation through electron-driven processes. This study investigates catalyst-free NH3 synthesis in a flowing water-electrode dielectric barrier discharge (DBD) reactor driven by alternating current (AC), unipolar pulse, and bipolar pulse. Electrical diagnostics and optical emission spectroscopy were used to examine how excitation mode affects discharge behavior, energy utilization, and nitrogen activation. Nanosecond pulsed excitation improved NH3 synthesis performance compared with AC excitation under the tested conditions. Unipolar pulsing was more favorable in the low specific energy input (SEI) regime, whereas bipolar pulsing maintained better performance at higher SEI, which was associated with discharge regulation induced by periodic field reversal. Optical emission analysis indicated that bipolar excitation showed a slightly higher mean effective reduced electric field, together with stronger N2+-related emission. These results suggest enhanced electron-impact excitation and ionization characteristics and highlight the role of excitation waveform in regulating discharge behavior and energy utilization in catalyst-free plasma-assisted ammonia synthesis.
Physics-Informed Neural Networks (PINNs) have emerged as a promising alternative for solving systems governed by partial differential equations (PDEs), such as the neutron diffusion equation. Here, conventional PINNs assume fixed PDE parameters, however, in reality, the material parameters inside a nuclear reactor core vary continuously. The variation renders the conventional fixed parameters PINNs unsuitable as the models must be retrained. To address this challenge, a parametric PINNs model is built so inferences can be made on various material properties without the need for retraining. This article aims to demonstrates the capabilities of PINNs in resolving the neutron diffusion equation with fixed parameters in both one-dimensional and two-dimensional geometries and compared to the reference finite difference solver. Then, the functionality of PINNs is extended by training the network across a range of material parameters pertaining to real physical changes in reactor conditions generated through OpenMC. The model is then verified against a reference solver on one-hundred random material properties within the OpenMC generated range, showing good agreement with the reference solution but with a vastly accelerated calculation routine.
Selective catalytic reduction technology using NH3 as a reducing agent is an effective method for abating the main air pollutants NOx from coal-fired industries, mobile exhausts, etc. However, suppressing the overoxidation of NH3 is a significant challenge. The over-oxidation of NH3 will generate NOx and N2O secondary pollutants, reducing the reduction efficiency. Achieving an optimal equilibrium between redox property and surface acidity is essential for the efficiency of NH3-SCR catalyst. Here, a Ru and H3PW12O40 (HPW) comodification method was employed to prepare the Ru-HPW/CeO2 catalyst by adjusting the redox property and acidity, achieving a significant leap in catalytic performance. Among the prepared catalysts, Ru-20HPW/ CeO2 demonstrated the most outstanding NOx removal efficiency, reaching over 80% NOx conversion at 200-350 degrees C. The characterization data indicate that the enhanced performance of Ru-20HPW/CeO2 is attributed to the equilibrium between its acidic properties and redox property. This originates from the presence of a large number of Br & Oslash;nsted acid sites that facilitate the adsorption of NH3, as well as an increased number of oxygen vacancies. This work provides a new strategy for constructing highly efficient and low-cost heterogeneous catalysts applied to environmental catalytic reactions.
Non-thermal plasma (NTP) catalysis provides a promising route for CO2 hydrogenation at room temperature and atmospheric pressure, avoiding the harsh conditions required in conventional thermocatalysis. Herein, the effect of discharge waveform on methanol formation over ZnCu/CeO2 catalysts was investigated. Among the catalysts studied, Zn1Cu2/CeO2 driven by sinusoidal AC plasma exhibited the best performance, achieving a CO2 conversion of 8.38% and a methanol selectivity of 65.97%, together with reduced energy consumption. Structural characterizations indicate that an optimized Zn/Cu ratio promotes an oxygen-vacancy-rich surface environment and defect-enriched Cu/Zn-Ce interfacial structures, which are beneficial for CO2 adsorption/activation and surface hydrogenation toward methanol. Under the investigated conditions, the discharge waveform strongly influences electron-energy characteristics, reactive species formation, and product distribution. AC plasma, with gradual voltage variation and relatively moderate electron-energy characteristics, is more favorable for mild CO2 activation and surface-mediated methanol formation. In contrast, nanosecond pulsed plasma, with nanosecondscale voltage rise and transient high-field events, tends to enhance gas-phase excitation, dissociation, ionization, and radical chemistry, leading to increased CO and hydrocarbon formation. These results suggest that product distribution in NTP-assisted CO2 hydrogenation can be regulated by synergistically tuning catalyst interfacial structures and plasma discharge waveforms under mild conditions.
Urban courtyards serve as important semi-enclosed spaces that influence residents’ acoustic comfort and psychological wellbeing, yet their perceptual qualities remain under-researched compared to street canyons. This study investigates how height-to-width ratio (H/W) and natural design features (trees, vegetation, and water elements) affect perceived enclosure and pleasantness in urban courtyards through multisensory assessment. A laboratory experiment was conducted using virtual reality environments and acoustic simulations with 33 participants who evaluated courtyards varying in H/W (0.3 and 1.0), size (750 m2 and 3,000 m2), and natural features across visual-only, audio-visual, and audio-only conditions. Results showed that higher H/W consistently increased perceived enclosure while reducing pleasantness in both visual-only and audio-visual conditions. Under audio-only conditions, H/W had negligible effects on pleasantness in small courtyards, though a modest but significant effect was observed in large courtyards (η2 = 0.14). Natural features, particularly trees with birdsong, significantly enhanced pleasantness (η2 = 0.18–0.48) and produced modest, context-dependent reductions in perceived enclosure (η2 = 0.08–0.15 for scenario effects). Larger courtyards were perceived as more pleasant and open (less enclosed) than smaller ones in both visual-only and audio-visual conditions. Audio-visual presentation generally increased perceived enclosure (lower openness scores), while also increasing pleasantness relative to the visual-only condition. These findings offer preliminary evidence-based insights that may inform courtyard design practice, with the caveat that all participants were Japanese and stimuli reflected Western courtyard typologies; cross-cultural replication with more diverse samples is needed before broader generalisation.
