THE KAUST Repository is an initiative of the University Library to expand the impact of conference papers, technical reports, peer-reviewed articles, preprints, theses, images, data sets, and other research-related works of King Abdullah University of Science and Technology (KAUST).
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Forecasting high-frequency spatio-temporal wind power with dimensionally reduced echo state networks(Journal of the Royal Statistical Society: Series C (Applied Statistics), Wiley, 2022-01-23) [Article]Fast and accurate hourly forecasts of wind speed and power are crucial in quantifying and planning the energy budget in the electric grid. Modelling wind at a high resolution brings forth considerable challenges given its turbulent and highly nonlinear dynamics. In developing countries, where wind farms over a large domain are currently under construction or consideration, this is even more challenging given the necessity of modelling wind over space as well. In this work, we propose a machine learning approach to model the nonlinear hourly wind dynamics in Saudi Arabia with a domain-specific choice of knots to reduce spatial dimensionality. Our results show that for locations highlighted as wind abundant by a previous work, our approach results in an 11% improvement in the 2-h-ahead forecasted power against operational standards in the wind energy sector, yielding a saving of nearly one million US dollars over a year under current market prices in Saudi Arabia.
Silicon carbide in catalysis: from inert bed filler to catalytic support and multifunctional material(Catalysis Reviews, Informa UK Limited, 2022-01-22) [Article]Silicon carbide (SiC) or carborundum has unparalleled thermal stability and conductivity compared with many other materials. This feature together with its unique photoelectrical properties (tunable band gap: 2.39–3.33 eV), low thermal expansion, high strength, and good chemical and thermal stability makes it an ideal inert solid in catalysis. The evolution of methods for synthesizing SiC has also progressively endowed it with additional features at the multiscale. This review tracks the development of SiC from a secondary to a leading role material in catalysis. First, the intrinsic properties of SiC are discussed and compared with other state-of-the-art catalytic materials. The synthetic methods are systematically reviewed and compared. Then, the applications of SiC in catalysis are assessed, paying particular attention to those that involve C1 chemistry (Fischer–Tropsch Synthesis and the valorization of CO2 and CH4), photocatalysis and biomass conversion. Finally, the potential future applications of SiC are also addressed and discussed.
Study on the effects of narrow-throat pre-chamber geometry on the pre-chamber jet velocity using dual formaldehyde PLIF imaging(Combustion and Flame, Elsevier BV, 2022-01-22) [Article]The effects of narrow-throat pre-chamber geometry on the main chamber combustion were investigated on a heavy-duty optical engine fueled with methane. Simultaneous dual formaldehyde PLIF imaging and OH* chemiluminescence imaging were applied to characterize the early-stage formaldehyde jet and flame jet discharge process. The formaldehyde jet velocity on the jet boundary was quantified by dual formaldehyde PLIF for the first time. Three narrow-throat pre-chambers with two rows of orifices on the nozzle and with different pre-chamber volume and inner throat diameter were studied under the same pre-chamber to main chamber fuel ratio and global excess air ratio of 2.0. The results indicate that the narrow-throat pre-chamber performance is not very sensitive to the pre-chamber volume. The pre-chamber with a larger volume produces only slightly higher pressure buildup in the pre-chamber () and similar main chamber combustion phasing and engine efficiency. The inner throat diameter is the key dimension in the narrow-throat pre-chamber design. A larger inner throat diameter produces a smaller peak and a slower jet penetration, resulting in longer combustion duration and lower engine efficiency. The formaldehyde PLIF shows that the main chamber combustion can be generally classified into two stages: the initial flame ignition and the following flame propagation. The maximum local formaldehyde jet boundary velocity of the narrow-throat pre-chamber with an inner throat diameter of 3.3 mm is up to about 280 m/s and it decreases dramatically when the inner throat diameter is increased to 5.3 mm. The flame jet characteristics of lower and upper orifices can be significantly different due to the local pressure difference between them in the pre-chamber throat. A smaller inner throat diameter results in a larger pressure difference between the lower and upper row orifices and could lead to weak upper-row flame jets. The narrow-throat pre-chamber design with an optimized inner throat diameter can produce high, fast jet penetration, and short combustion duration, which favor the lean limit operation and high engine efficiency.
iSCAN-V2: A One-Pot RT-RPA–CRISPR/Cas12b Assay for Point-of-Care SARS-CoV-2 Detection(Frontiers in Bioengineering and Biotechnology, Frontiers Media SA, 2022-01-21) [Article]Rapid, specific, and sensitive detection platforms are prerequisites for early pathogen detection to efficiently contain and control the spread of contagious diseases. Robust and portable point-of-care (POC) methods are indispensable for mass screening of SARS-CoV-2. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-based nucleic acid detection technologies coupled with isothermal amplification methods provide a straightforward and easy-to-handle platform for detecting SARS-CoV-2 at POC, low-resource settings. Recently, we developed iSCAN, a two-pot system based on coupled loop-mediated isothermal amplification (LAMP) and CRISPR/Cas12a reactions. However, in two-pot systems, the tubes must be opened to conduct both reactions; two-pot systems thus have higher inherent risks of cross-contamination and a more cumbersome workflow. In this study, we developed and optimized iSCAN-V2, a one-pot reverse transcription-recombinase polymerase amplification (RT-RPA)-coupled CRISPR/Cas12b-based assay for SARS-CoV-2 detection, at a single temperature in less than an hour. Compared to Cas12a, Cas12b worked more efficiently in the iSCAN-V2 detection platform. We assessed and determined the critical factors, and present detailed guidelines and considerations for developing and establishing a one-pot assay. Clinical validation of our iSCAN-V2 detection module with reverse transcription-quantitative PCR (RT-qPCR) on patient samples showed 93.75% sensitivity and 100% specificity. Furthermore, we coupled our assay with a low-cost, commercially available fluorescence visualizer to enable its in-field deployment and use for SARS-CoV-2 detection. Taken together, our optimized iSCAN-V2 detection platform displays critical features of a POC molecular diagnostic device to enable mass-scale screening of SARS-CoV-2 in low-resource settings.
MXene-Coated Membranes for Autonomous Solar-Driven Desalination(ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-01-21) [Article]Clean water supply in off-grid locations remains a stumbling stone for socio-economic development in remote areas where solar energy is abundant. In this regard, several technologies have already introduced various solutions to the off-grid freshwater predicament; however, most of them are either costly or complex to operate. Nonetheless, photothermal membrane distillation (PMD) has emerged as a promising candidate with great potential to be autonomously driven by solar energy. Instead of using energy-intensive bulk feed heating in conventional MD systems, PMD membranes can directly harvest the incident solar light at the membrane interface as an alternative driving energy resource for the desalination process. Because of its excellent photothermal properties and stability in ionic environments, herein, Ti3C2Tx MXene was coated onto commercial polytetrafluoroethylene (PTFE) membranes to allow for a self-heated PMD process. An average water vapor flux of 0.77 kg/m2 h with an excellent temporal response under intermitting lighting and a photothermal efficiency of 65.3% were achieved by the PMD membrane under one-sun irradiation for a feed salinity of 0.36 g/L. Naturally, the efficiency of the process decreased with higher feed concentrations due to the reduction of the evaporation rate and the scattering of incident sunlight toward the membrane photothermal surface, especially at rates above 10 g/L. Notably, with such performance, 1 m2 of the MXene-coated PMD membrane can fulfill the recommended daily potable water intake for a household, that is, ca. 6 L/day.