Towards Deep Attention in Graph Neural Networks: Problems and Remedies

Graph neural networks (GNNs) learn the representation of graph-structured data, and their expressiveness can be further enhanced by inferring node relations for propagation. Attention-based GNNs infer neighbor importance to manipulate the weight of its propagation. Despite their popularity, the discussion on deep graph attention and its unique challenges has been limited. In this work, we investigate some problematic phenomena related to deep graph attention, including vulnerability to over-smoothed features and smooth cumulative attention. Through theoretical and empirical analyses, we show that various attention-based GNNs suffer from these problems. Motivated by our findings, we propose AEROGNN, a novel GNN architecture designed for deep graph attention. AERO-GNN provably mitigates the proposed problems of deep graph attention, which is further empirically demonstrated with (a) its adaptive and less smooth attention functions and (b) higher performance at deep layers (up to 64). On 9 out of 12 node classification benchmarks, AERO-GNN outperforms the baseline GNNs, highlighting the advantages of deep graph attention. Our code is available at https://github.com/syleeheal/AERO-GNN.Comment: 22 pages, 6 figures, conference paper, published in International Conference on Machine Learning. PMLR, 202

Bio-inspired dewetted surfaces based on SiC/Si interlocked structures for enhanced-underwater stability and regenerative-drag reduction capability

Drag reduction has become a serious issue in recent years in terms of energy conservation and environmental protection. Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency. However, due to limited lifetime of plastron (i.e., air pockets) on superhydrophobic surfaces in underwater, the instability of dewetted surfaces has been a sticking point for practical applications. This work presents a breakthrough in improving the underwater stability of superhydrophobic surfaces by optimizing nanoscale surface structures using SiC/Si interlocked structures. These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities, with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%. Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.119Ysciescopu

Photocatalytic Ohmic layered nanocomposite for efficient utilization of visible light photons

The WO3/W/PbBi2Nb1.9Ti0.1O9 photocatalyst was fabricated by depositing the tungsten clusters over the p-type perovskite base material with the chemical vapor deposition method, and later partly oxidizing the surfaces of these clusters to obtain n-type WO3 overlayers and W metal layer as an Ohmic junction. This NCPC showed unprecedented high activity for the photocatalytic oxidation of water, photocurrent generation, and acetaldehyde decomposition under visible light irradiation (lambda >= 420 nm). (c) 2006 American Institute of Physicsclose313

Synthesis and Characterization of ZnO Nanowire–CdO Composite Nanostructures

ZnO nanowire–CdO composite nanostructures were fabricated by a simple two-step process involving ammonia solution method and thermal evaporation. First, ZnO nanowires (NWs) were grown on Si substrate by aqueous ammonia solution method and then CdO was deposited on these ZnO NWs by thermal evaporation of cadmium chloride powder. The surface morphology and structure of the synthesized composite structures were analyzed by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The optical absorbance spectrum showed that ZnO NW–CdO composites can absorb light up to 550 nm. The photoluminescence spectrum of the composite structure does not show any CdO-related emission peak and also there was no band gap modification of ZnO due to CdO. The photocurrent measurements showed that ZnO NW–CdO composite structures have better photocurrent when compared with the bare ZnO NWs

Synthesis of Novel Double-Layer Nanostructures of SiC–WOxby a Two Step Thermal Evaporation Process

A novel double-layer nanostructure of silicon carbide and tungsten oxide is synthesized by a two-step thermal evaporation process using NiO as the catalyst. First, SiC nanowires are grown on Si substrate and then high density W18O49nanorods are grown on these SiC nanowires to form a double-layer nanostructure. XRD and TEM analysis revealed that the synthesized nanostructures are well crystalline. The growth of W18O49nanorods on SiC nanowires is explained on the basis of vapor–solid (VS) mechanism. The reasonably better turn-on field (5.4 V/μm) measured from the field emission measurements suggest that the synthesized nanostructures could be used as potential field emitters

Recycling Rare-Earth Slag for Enhanced Photoelectro- chemical Efficiency of a Reduced Graphene Oxide-Covered CdSe@ZnO Hetero-Nanostructured Photoanode

Breakthroughs in efficient recycling of industrial slag and renewable energy have become subjects of global interest. In this study, rare-earth oxide (REO) slag is used for the first time in dramatically enhanced photoelectrochemical hydrogen generation by modifying the surface of a photoanode, which is constructed from reduced graphene oxide (RGO)-covered CdSe@ZnO two-story hetero-nanostructures. REO slag is extracted from REO iron ore by mimicking of the ironmaking process, and whole hetero-nanostructures prepared for photoelectrochemical anode are synthesized by the hydrothermal method. These studies demonstrate that the REO slag significantly promotes the growth of CdSe nanoparticles and can also be used as the OH- source to block hydrolysis of Na2S and Na2SO3 in the electrolyte. Moreover, light absorption is fully facilitated by the two-story structure, and the photocon-version is enhanced via type II cascade band alignment of CdSe and ZnO. In addition, the concentration of holes and efficient charge transfer by RGO can suppress electron-hole recombination and improve the electron lifetime. This study presents a novel REO-slag-modified photoanode for high efficiency photoelectrochemical devices and offers the possibility of recycling industrial waste for renewable energy generation.115Nsciescopu

Novel Heterostructure of CdSe Nanobridge on ZnO Nanorods: Cd-Carboxyl-RGO-Assisted Synthesis and Enhanced Photoelectrochemical Efficiency

Photoelectrochemical (PEC) hydrogen generation is a green and effective strategy for addressing energy crises. In this study, a CdSe heteronanobridge (HNB) structure is fabricated as PEC photoanode via a hydrothermal method. The "pier" is built using ZnO nanorods (NRs) decorated with CdSe nanoparticles (NPs), and the "bridge" is constructed using CdSe nanowire covered by an reduced graphene oxide (RGO) layer and cross-linked with ZnO NRs. The formation of the CdSe NBs is ascribed to the passivation of the CdSe nonpolar surface with an RGO layer by the formation of Cd-carboxyl-RGO bond in alkaline solution, which directs the preferential growth of CdSe along c-axis. Additionally, despite etching the functionalized RGO with HAuCl 4 solution, CdSe NBs decorated with Au NPs are also synthesized as another heteronanostructure. This study demonstrates that the photoconversion of the CdSe hetero-NBs can be enhanced via the type II cascade band alignment of CdSe and ZnO and efficient charge transfer through net-like bridge structures. Moreover, the Cd-carboxyl-RGO layer and Au NPs can improve the electron lifetime of the CdSe NBs by suppressing electron-hole recombination. Overall, CdSe hetero-NBs with increased PEC efficiency represent a promising photoanode material, and the synthesis route can be used to build highly networked heteronanostructures of other materials.1110Nsciescopu