King Abdullah University of Science and Technology

About: King Abdullah University of Science and Technology is a education organization based out in Jeddah, Saudi Arabia. It is known for research contribution in the topics: Membrane & Catalysis. The organization has 6221 authors who have published 22019 publications receiving 625706 citations. The organization is also known as: KAUST.

Perovskite Nanocrystals as a Color Converter for Visible Light Communication

Abstract: Visible light communication (VLC) is an emerging technology that uses light-emitting diodes (LEDs) or laser diodes for simultaneous illumination and data communication. This technology is envisioned to be a major part of the solution to the current bottlenecks in data and wireless communication. However, the conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC. In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr3 perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr3 NC phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is ∼40 times greater than that of conventional phosphors, and the capability to transmit a high data rate of up to 2 Gbit/s. Moreover, this perovskite-enhanced white light source combines ultrafast response characteristics with a h...

What can NMR spectroscopy of selenoureas and phosphinidenes teach us about the π-accepting abilities of N-heterocyclic carbenes?

Abstract: selenoureas derived from a range of imidazol-2-ylidenes, 4,5-dihydroimidazol-2-ylidenes and triazol-2ylidenes are documented. Computational studies are used to explore the link between the shielding of the selenium centre and the electronic properties of the NHCs. Results show that dSe is correlated to the energy gap between a filled lone pair orbital on Se and the empty p* orbital corresponding to the Se–NHC bond. Bond energy decomposition analysis indicated no correlation between the orbital s-contribution to bonding and the chemical shielding, while a good correlation was found between the p-contribution to bonding and the chemical shielding, confirming that this technique is indeed able to quantify the ability of NHCs to accept p-electron density. Calculations conducted on phosphinidene adducts yielded similar results. With the link between dSe and dP and p-back bonding ability clearly established, these compounds represent useful ways in which to fully understand and quantify this aspect of the electronic properties of NHCs.

Stochastic Spectral Galerkin and Collocation Methods for PDEs with Random Coefficients: A Numerical Comparison

Abstract: Much attention has recently been devoted to the development of Stochastic Galerkin (SG) and Stochastic Collocation (SC) methods for uncertainty quantification. An open and relevant research topic is the comparison of these two methods. By introducing a suitable generalization of the classical sparse grid SC method, we are able to compare SG and SC on the same underlying multivariate polynomial space in terms of accuracy vs. computational work. The approximation spaces considered here include isotropic and anisotropic versions of Tensor Product (TP), Total Degree (TD), Hyperbolic Cross (HC) and Smolyak (SM) polynomials. Numerical results for linear elliptic SPDEs indicate a slight computational work advantage of isotropic SC over SG, with SC-SM and SG-TD being the best choices of approximation spaces for each method. Finally, numerical results corroborate the optimality of the theoretical estimate of anisotropy ratios introduced by the authors in a previous work for the construction of anisotropic approximation spaces.

H2S Sensors: Fumarate-Based fcu-MOF Thin Film Grown on a Capacitive Interdigitated Electrode

Abstract: Herein we report the fabrication of an advanced sensor for the detection of hydrogen sulfide (H2S) at room temperature, using thin films of rare-earth metal (RE)-based metal–organic framework (MOF) with underlying fcu topology This unique MOF-based sensor is made via the in situ growth of fumarate-based fcu-MOF (fum-fcu-MOF) thin film on a capacitive interdigitated electrode The sensor showed a remarkable detection sensitivity for H2S at concentrations down to 100 ppb, with the lower detection limit around 5 ppb The fum-fcu-MOF sensor exhibits a highly desirable detection selectivity towards H2S vs CH4, NO2, H2, and C7H8 as well as an outstanding H2S sensing stability as compared to other reported MOFs

Federated Learning of a Mixture of Global and Local Models

Abstract: We propose a new optimization formulation for training federated learning models. The standard formulation has the form of an empirical risk minimization problem constructed to find a single global model trained from the private data stored across all participating devices. In contrast, our formulation seeks an explicit trade-off between this traditional global model and the local models, which can be learned by each device from its own private data without any communication. Further, we develop several efficient variants of SGD (with and without partial participation and with and without variance reduction) for solving the new formulation and prove communication complexity guarantees. Notably, our methods are similar but not identical to federated averaging / local SGD, thus shedding some light on the essence of the elusive method. In particular, our methods do not perform full averaging steps and instead merely take steps towards averaging. We argue for the benefits of this new paradigm for federated learning.