| 184931. |
- Li, S., et al.
(författare)
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Crystallographic structures of PbWO4
- 2003
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 23:3, s. 343-347
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Tidskriftsartikel (refereegranskat)
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| 184932. |
- Li, Shicheng, et al.
(författare)
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Data-driven prediction of cylinder-induced unsteady wake flow
- 2024
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Ingår i: Applied Ocean Research. - : Elsevier. - 0141-1187 .- 1879-1549. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Understanding cylinder-induced wake is pivotal in fluid dynamics, providing essential insights for the design and analysis of various structures, including offshore platforms, bridges, and buildings. To achieve fast and accurate modeling, this study introduces a novel reduced-order model (ROM) utilizing dynamic mode decomposition (DMD) and an advanced deep learning framework, specifically an attention-enhanced convolutional neural network-long short-term memory networks model (CNN-LSTM), for predicting cylinder-induced unsteady wake flows. The DMD efficiently simplifies complex fluid systems while retaining key dynamics, thus significantly saving computational costs. By leveraging its combined strengths, the CNN-LSTM with an attention mechanism effectively captures complex spatiotemporal features. The resulting ROM accurately reproduces the wake processes around a cylinder (group), demonstrating high consistency with computational fluid dynamics (CFD) solutions (coefficient of determination > 0.98), and showcases satisfactory resilience to a (Gaussian) noise level of up to 25 %. This study contributes a robust ROM capable of handling spatiotemporal dynamics, facilitating swift prediction of future outcomes using historical data, which is particularly critical for efficient real-time analysis and informed decision-making in dynamic settings, e.g., digital twins and predictive maintenance.
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| 184933. |
- Li, Siyu, et al.
(författare)
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Dearomatization drives complexity generation in freshwater organic matter
- 2024
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Ingår i: Nature. - : NATURE PORTFOLIO. - 0028-0836 .- 1476-4687. ; 628:8009
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain 1-3 . Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle 4,5 . Here we use complementary multiplicity-edited 13C nuclear magnetic resonance (NMR) spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthetic chemistry to create natural product scaffolds 6-10 , is probably a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OCqC3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin-derived and tannin-derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones, which are subject to immediate and parallel cycloadditions. This combination leads to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity acceleration in the processing of DOM molecules, creation of new oxygenated aliphatic molecules and that it could be prevalent in nature. Using complementary multiplicity-edited 13C nuclear magnetic resonance spectra, oxidative dearomatization is shown to be a key driver for generating structural diversity during processing of dissolved organic matter and the data also suggest high abundance of OCqC3 units.
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| 184934. |
- Li, Sa, et al.
(författare)
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Dehydrogenation associated with Ti catalyst in sodium alanate
- 2010
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Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 71:8, s. 1073-1076
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Tidskriftsartikel (refereegranskat)abstract
- Addition of small amount of Ti precursors to sodium alanate has recently been found to substantially improve the kinetics and thermodynamics of hydrogen sorption in sodium alanate. In spite of several attempts, a fundamental understanding of how the catalyst works has remained unattainable. Using first principles methods we have investigated the mechanisms for hydrogen desorption in this material. We conclude that Ti substituted at Al site is energetically most favorable. The small amount of Ti substitution does not introduce large lattice distortion. The Ti atom serves as a magnet that continues to attract nearby H atoms as the nearest ones are successively desorbed. The number of Al atoms near to the Ti site remains at four upon hydrogen desorption when Ti is substituted at the Al site. These results provide important new insight into the design of future catalysts for hydrogen storage materials.
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| 184935. |
- Li, S., et al.
(författare)
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Dehydrogenation Mechanism in Catalyst-activated MgH2
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:13, s. 132106-
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Tidskriftsartikel (refereegranskat)abstract
- A small amount of Nb2O5 catalyst is known to substantially improve the desorption thermodynamics and kinetics of MgH2. Using density functional theory in combination with ab initio molecular dynamics simulation, we provide theoretical understanding of the mechanism of dehydrogenation in Nb doped MgH2. We show that the substitution of Nb at the Mg site followed by the clustering of H around Nb is a likely pathway for hydrogen desorption. We also find that dehydrogenation from the vicinity of Mg vacancies is exothermic. However, the vacancies are not likely to play a significant role in hydrogen desorption due to their high formation energy (3.87 eV).
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| 184936. |
- Li, Shenghui, 1994-, et al.
(författare)
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Demo Abstract : Blades: A Unified Benchmark Suite for Byzantine-Resilient in Federated Learning
- 2024
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Ingår i: 9TH ACM/IEEE CONFERENCE ON INTERNET OF THINGS DESIGN AND IMPLEMENTATION, IOTDI 2024. - : IEEE Computer Society. - 9798350370256 - 9798350370263 ; , s. 229-230
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Konferensbidrag (refereegranskat)abstract
- Federated learning (FL) facilitates distributed training across different IoT and edge devices, safeguarding the privacy of their data. The inherently distributed nature of FL introduces vulnerabilities, especially from adversarial devices aiming to skew local updates to their desire. Despite the plethora of research focusing on Byzantine-resilient FL, the academic conununity has yet to establish a comprehensive benchmark suite, pivotal for the assessment and comparison of different techniques. This demonstration presents Blades, a scalable, extensible, and easily configurable benchmark suite that supports researchers and developers in efficiently implementing and validating strategies against baseline algorithms in Byzantine-resilient FL.
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| 184937. |
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| 184938. |
- Li, S., et al.
(författare)
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Dielectric chain driven by electron-hole plasma photoexcitation
- 2017
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Ingår i: Proceedings of the International Conference Days on Diffraction 2017, DD 2017. - 9781538647967 ; 2017-December, s. 214-218
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Konferensbidrag (refereegranskat)abstract
- All-dielectric nanophotonics based on high-index dielectric nanoparticles became a powerful platform for modern light science, providing many fascinating applications, including high-efficient nanoantennas and metamaterials. High-index dielectric nanostructures are of a special interest for nonlinear nanophotonics, where they demonstrate special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel type of highly tunable all-dielectric Yagi-Uda nanoantennas, consisting of a chain of Si nanoparticles exciting by an electric dipole source, which allow tuning of their radiating properties via electron-hole plasma photoexcitation. We theoretically and numerically demonstrate the tuning of radiation power patterns and the Purcell factor by additional pumping of several boundary nanoparticles with relatively low peak intensities of fs-laser.
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| 184939. |
- Li, S., et al.
(författare)
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Dielectric Yagi-Uda nanoantennas driven by electron-hole plasma photoexcitation
- 2017
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 917:6
-
Konferensbidrag (refereegranskat)abstract
- All-dielectric nanophotonics based on high-index dielectric nanoparticles became a powerful platform for modern light science, providing many fascinating applications, including high-efficient nanoantennas and metamaterials. High-index dielectric nanostructures are of a special interest for nonlinear nanophotonics, where they demonstrate special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel type of highly tunable all-dielectric Yagi-Uda nanoantennas, consisting of a chain of Si nanoparticles exciting by an electric dipole source, which allow tuning of their radiating properties via electron-hole plasma photoexcitation. We theoretically and numerically demonstrate the tuning of radiation power patterns and the Purcell effect by additional pumping of several boundary nanoparticles with relatively low peak intensities of fs-laser.
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| 184940. |
- Li, Shuting, et al.
(författare)
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Direct structure determination of vemurafenib polymorphism from compact spherulites using 3D electron diffraction
- 2023
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Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The spherulitic morphology is considered to be the most common morphology of crystalline materials and is particularly apparent in melt-crystallized products. Yet, historically, the polycrystalline nature of spherulites has hindered successful crystal structure determination. Here, we report the direct structure determination of a clinical drug, vemurafenib (VMN), in compact spherulite form using 3D electron diffraction (3D ED). VMN has four known polymorphs. We first solved the crystal structures of α-, β-, and γ-VMN from compact spherulites using 3D ED, and the resulting structures were highly consistent with those obtained by single-crystal X-ray diffraction. We then determined the crystal structure of δ-VMN—the least stable polymorph which cannot be cultivated as a single crystal—directly from the compact spherulite sample. We unexpectedly discovered a new polymorph during our studies, denoted as ε-VMN. Single crystals of ε-VMN are extremely thin and not suitable for study by X-ray diffraction. Again, we determined the structure of ε-VMN in a compact spherulite form. This successful structure elucidation of all five VMN polymorphs demonstrates the possibility of directly determining structures from melt-grown compact spherulite samples. Thereby, this discovery will improve the efficiency and broaden the scope of polymorphism research, especially within the field of melt crystallization.
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