A Survey on Solving and Discovering Differential Equations Using Deep Neural Networks

Ordinary and partial differential equations (DE) are used extensively in scientific and mathematical domains to model physical systems. Current literature has focused primarily on deep neural network (DNN) based methods for solving a specific DE or a family of DEs. Research communities with a history of using DE models may view DNN-based differential equation solvers (DNN-DEs) as a faster and transferable alternative to current numerical methods. However, there is a lack of systematic surveys detailing the use of DNN-DE methods across physical application domains and a generalized taxonomy to guide future research. This paper surveys and classifies previous works and provides an educational tutorial for senior practitioners, professionals, and graduate students in engineering and computer science. First, we propose a taxonomy to navigate domains of DE systems studied under the umbrella of DNN-DE. Second, we examine the theory and performance of the Physics Informed Neural Network (PINN) to demonstrate how the influential DNN-DE architecture mathematically solves a system of equations. Third, to reinforce the key ideas of solving and discovery of DEs using DNN, we provide a tutorial using DeepXDE, a Python package for developing PINNs, to develop DNN-DEs for solving and discovering a classic DE, the linear transport equation.Comment: Under review for ACM Computing Surveys journal. 29 page

Deposition of Crystalline GdIG Samples Using Metal Organic Decomposition Method

Fabrication of high quality ferrimagnetic insulators is an essential step for ultrafast magnonics, which utilizes antiferromagnetic exchange of the ferrimagnetic materials. In this work, we deposit high-quality GdIG thin films on a (111)-oriented GGG substrate using the Metal Organic Decomposition (MOD) method, a simple and high throughput method for depositing thin film materials. We postannealed samples at various temperatures and examined the effect on structural properties such as crystallinity and surface morphology. We found a transition in the growth mode that radically changes the morphology of the film as a function of annealing temperature and obtained an optimal annealing temperature for a uniform thin film with high crystallinity. Optimized GdIG has a high potential for spin wave applications with a low damping parameter in the order of 10(-3), which persists down to cryogenic temperatures

A scalable molecule-based magnetic thin film for spin-thermoelectric energy conversion

Spin thermoelectrics, an emerging thermoelectric technology, offers energy harvesting from waste heat with potential advantages of scalability and energy conversion efficiency, thanks to orthogonal paths for heat and charge flow. However, magnetic insulators previously used for spin thermoelectrics pose challenges for scale-up due to high temperature processing and difficulty in large-area deposition. Here, we introduce a molecule-based magnetic film for spin thermoelectric applications because it entails versatile synthetic routes in addition to weak spin-lattice interaction and low thermal conductivity. Thin films of Cr-II[Cr-III(CN)(6)], Prussian blue analogue, electrochemically deposited on Cr electrodes at room temperature show effective spin thermoelectricity. Moreover, the ferromagnetic resonance studies exhibit an extremely low Gilbert damping constant -(2.4 +/- 0.67) x10(-4), indicating low loss of heat-generated magnons. The demonstrated STE applications of a new class of magnet will pave the way for versatile recycling of ubiquitous waste heat

Direct interspecies electron transfer enables anaerobic oxidation of sulfide to elemental sulfur coupled with CO2-reducing methanogenesis

Electric syntrophy between fatty acid oxidizers and methanogens through direct interspecies electron transfer (DIET) is essential for balancing acidogenesis and methanogenesis in anaerobic digestion. Promoting DIET using electrically conductive additives proved effective in enhancing methanogenesis; however, its possibility to affect other microbial redox reactions in methanogenic systems has been little studied. This study provides the first confirmation of the electrosyntrophic coupling of sulfide oxidation to S0 with CO2-reducing methanogenesis in sulfur-rich methanogenic cultures supplemented with conductive magnetite (100-700-nm particle size). The H2S content in biogas, initially exceeding 5000 ppmv, decreased to below 1 ppmv along with an accumulation of extracellular S0 (60-70 mg/L; initially <1 mg/L) at a magnetite dose of 20 mM Fe, while there were no significant changes in methane yield. A comprehensive polyphasic approach demonstrated that the S0 formation occurs through electro-syntrophic oxidation of sulfide coupled with CO2-reducing methanogenesis, involving Methanothrix as the dominant methanogen

Performance and Microbial Community analysis on denitrification of electronic wastewater using various External Carbon Source

Objectives In the biological denitrification process of electronic wastewater, the denitrification performance of various types of external carbon sources and the changes in the bacterial community before and after denitrification were evaluated through NGS analysis. Methods After selecting 6 types of external carbon sources, the concentration of nitrate nitrogen was analyzed for 6 hours under anoxic conditions with a C/N ratio of 4 to evaluate the denitrification rate, and the changes in the community distribution of bacteria before and after denitrification were confirmed through NGS analysis. Results and Discussion As a result of comparing the denitrification performance of various external carbon sources, Ethylene glycol(EG) was the best at 79.9% after 6 hours, and the specific denitrification rate(SDNR) was 1.000mg NO3--N removal/g MLVSS·hr. The bacterial community change using NGS was distributed more than 90% of 10 phylums at the phylum level, and Proteobacteria, Saccharibacteria, and Chloroflexi were dominant, and among them, Saccharibacteria and Chloroflexi were confirmed to be bacteria contributing to denitrification. At class and genus level, when a external carbon source was added, the number of γ-proteobacteria increased in all experimental conditions, but the distribution of denitrifying bacteria was less than 1.27%, indicating that various bacteria contributed to denitrification. Conclusion In the case of Ethylene glycol(EG), it is judged that it can be used as an external carbon source, and there was no significant change in the community depending on the type of carbon source injected, and various bacteria such as Saccharibacteria and Chloroflexi contributed to denitrification and eliminated nitrogen pollutants

Surface Roughening Strategy for Highly Efficient Bifunctional Electrocatalyst: Combination of Atomic Layer Deposition and Anion Exchange Reaction

Electrocatalytic water splitting, which is an interface-dominated process, can be significantly accelerated by increasing the number of front-line surface active sites (N-A) of the electrocatalyst. In this study, a unique method is used for increasing the N-A by converting the smooth ultrathin atomic-layer-deposited nanoshells of the electrocatalysts into nano-roughened active shell layers using a controlled anion-exchange reaction (AER). The coarse thin nanoshells present abundant surface active sites, which are generated owing to the inherent unit-cell volume mismatch induced during the AER. Consequently, the nano-roughened electrodes accelerate the sluggish water reaction kinetics and lower the overpotentials required for the hydrogen and oxygen evolution reactions. In addition, the electronic modulation induced by the nanoshell layer at the core-nanoshell interface amplifies the local electron density, as confirmed using electrochemical analysis data and density functional theory calculations. Because of the integrity of the composite electrodes during water-splitting half-cell reactions, their durability for industrial seawater electrolysis is evaluated. The results indicate that their electrochemical activity does not change significantly after 10 days of continuous overall water splitting.11Nsciescopu

Atomic layer deposition-triggered hierarchical core/shell stable bifunctional electrocatalysts for overall water splitting

The precise design of nanomaterials is a promising approach, but remains a challenge toward the development of highly efficient catalysts in water splitting applications. Herein, a facile three-step process to rationally design advanced NiCo2O4/MoO2@atomic layer deposition (ALD)-NiO heteronanostructure arrays on a nickel foam substrate is reported. By effective interface construction, the optimal electronic structure and coordination environment are created at the interface in the heteronanostructure, which can provide rich reaction sites and short ion diffusion paths. Notably, density functional theory calculations reveal that the MoO2@ALD-NiO nanointerface exhibits highly appropriate energetics for alkaline oxygen/hydrogen evolution reactions (OER/HER), thereby accelerating the enhancement in electrochemical activities. Benefiting from the heteronanostructure containing abundant nanointerfaces, NiCo2O4/MoO2@ALD-NiO displays remarkable HER (57.1 mV at 10 mA cm−2) and OER (372.3 mV at 100 mA cm−2) activities and excellent long-term stability in a 1 M KOH solution. This study provides new insight into the catalytic design of cost-effective electrocatalysts for future renewable energy systems.11Nsciescopu

Bio-Inspired Catecholamine-Derived Surface Modifier for Graphene-Based Organic Solar Cells

Owing to the growing interest in next-generation solar cells as a clean and renewable energy source, the demand for alternative transparent conducting electrodes (TCEs) has also increased. Although indium tin oxide (ITO) has been widely used as the standard TCE, its chemical and mechanical instabilities limit its widespread use in emerging photovoltaics. Graphene has attracted much attention as a potential alternative TCE owing to its excellent physical, optical, and electrical properties. However, owing to the inert nature of graphene with a hydrophobic surface, a significant amount of research has been devoted to resolve the nonwetting issue of charge-transporting materials on graphene. In this study, a thin layer of norepinephrine, an amphiphilic catecholamine derivative, was applied to graphene as a hydrophilic surface modifier to enable efficient surface modification without significantly decreasing the optical transmittance or the electrical conductivity. This modification allowed a commonly used hole-transporting material to be applied uniformly to the surface. Thus, the power conversion efficiency (PCE) of organic solar cells (OSCs) fabricated with this poly(norepinephrine)-coated graphene electrode was 7.93%, which is approaching close to that of the ITO-based reference device with a PCE of 8.73%. This work represents the first demonstration of an adhesive biomaterial as an efficient surface modifier for chemically inert graphene and its successful application in OSCs, which shows promise for the future development of bio-inspired graphene systems for applications to various optoelectronic devices