Virtual screenings can accelerate and reduce the cost of discovering metal-organic frameworks (MOFs) for their applications in gas storage, separation, and sensing. In molecular simulations of gas adsorption/diffusion in MOFs, the adsorbate-MOF electrostatic interaction is typically modeled by placing partial point charges on the atoms of the MOF. For the virtual screening of large libraries of MOFs, it is critical to develop computationally inexpensive methods to assign atomic partial charges to MOFs that accurately reproduce the electrostatic potential in their pores. Herein, we design and train a message passing neural network (MPNN) to predict the atomic partial charges on MOFs under a charge neutral constraint. A set of ca. 2,250 MOFs labeled with high-fidelity partial charges, derived from periodic electronic structure calculations, serves as training examples. In an end-to-end manner, from charge-labeled crystal graphs representing MOFs, our MPNN machine-learns features of the local bonding environments of the atoms and learns to predict partial atomic charges from these features. Our trained MPNN assigns high-fidelity partial point charges to MOFs with orders of magnitude lower computational cost than electronic structure calculations. To enhance the accuracy of virtual screenings of large libraries of MOFs for their adsorption-based applications, we make our trained MPNN model and MPNN-charge-assigned computation-ready, experimental MOF structures publicly available. File list (2) download file view on ChemRxiv Message_passing_networks_to_learn_MOF_charges.pdf (3.62 MiB) download file view on ChemRxiv Message_passing_networks_to_learn_MOF_charges_SI.... (1.55 MiB)
Nanoporous materials (NPMs) selectively adsorb and concentrate gases into their pores, and thus could be used to store, capture, and sense many different gases. Modularly synthesized classes of NPMs, such as covalent organic frameworks (COFs), offer a large number of candidate structures for each adsorption task. A complete NPM-property table, containing measurements of the relevant adsorption properties in the candidate NPMs, would enable the matching of NPMs with adsorption tasks. However, in practice the NPM-property matrix is only partially observed (incomplete); (i) many properties of any given NPM have not been measured and (ii) any given property has not been measured for all NPMs.The idea in this work is to leverage the observed (NPM, property) values to impute the missing ones. Similarly, commercial recommendation systems impute missing entries in an incomplete product-customer ratings matrix to recommend products to customers. We demonstrate a COF recommendation system to match COFs with adsorption tasks by training a low rank model of an incomplete COF-adsorption-property matrix. A low rank model, trained on the observed (COF, adsorption property) values, provides (i) predictions of the missing (COF, adsorption property) values and (ii) a "map" of COFs, wherein COFs, represented as points, with similar (dissimilar) adsorption properties congregate (separate). We find the performance of the COF recommendation system varies for different adsorption tasks and diminishes precipitously when the fraction of missing entries exceeds 60 %. The concepts in our COF recommendation system can be applied broadly to many different materials and properties.
Abstract-In the realm of substation automation (SA), communication infrastructure plays a vital role in mediating between physical and virtual worlds of substation. Specification of data exchanges through standardized communication stacks is therefore an important issue for all substation equipment manufacturers seeking to provide vendor interoperability. Nowadays competitive electric utility marketplace, reliable and real-time information become the key factor for reliable delivery of power to the endusers, profitability of the electric utility and customer satisfaction. The operational and commercial demands of electric utilities require a high-performance data communication network that supports both existing functionalities and future operational requirements. As communication arena is changing day by day, the need for efficient and reliable communication infrastructure to address SA is evident. In this respect, a communication network constitutes the core of the SA, thus the design of cost-effective and reliable network architecture is a crucial task. Most of the existing communication networks claim to address the need of communication architecture for SA but in some regard these claims just could not fulfill the constraints imposed by highly available environment for SA. This paper presents a survey and analysis of the current state-of-the-art communication infrastructure in the SA. As Ethernet technology becomes more reliable and also widely available with fiber optical communication so this paper also examines the key issues and requirements for Ethernet in the substation environment and also opens some research challenges.
Increase in demand for broadband data services in the public safety domain is driving mobile network operators to consider different strategic options to deliver mission critical requirements. Utility service providers requiring enhanced data services for specialist applications are also being driven in a similar way. Partnering with existing commercial LTE network operators and providing these services as a mobile virtual network operator is being considered as a short term tactical solution within a long term strategic view in light of pending standards development. The scheduled release of these developments means that use cases comparable or equivalent to those delivered in TETRA networks will take time to be full realizable. To align with the spectrum of requirements around the concepts of Smart Cities, a different approach has to be sought. This paper provides a brief survey of use cases and requirements for public safety services, discusses the radio and core technology enhancements and identifies the risks with selecting partnership based strategies. A proposed strategy for Public Safety Mission Critical LTE networks forms a key contribution towards Smart City evolution.
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