| 1. |
- Chen, Bin, et al.
(författare)
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Full-colour luminescent compounds based on anthracene and 2,2 '-dipyridylamine
- 2013
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 1:44, s. 7409-7417
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Tidskriftsartikel (refereegranskat)abstract
- Starting from two simple units of anthracene and 2,2'-dipyridylamine, a series of new luminescent compounds 1-8 were designed and synthesized by a combined strategy of changing the connection mode between the two units, extending the conjugation size, and introducing an additional electron donor. Photophysical properties of 1-8 were investigated and discussed on the basis of solvatochromic behaviour, theoretical calculations, crystal structure, and optimized structures. Interestingly, the emission wavelengths of these compounds could be successfully tuned from violet to red both in solutions and the solid-state, and prominent positive solvatochromism was observed for the compounds with a D-p-A framework. Consider compound 7 as an example, it shows peaks at 526 nm and 627 nm in cyclohexane and DMSO, respectively. Meanwhile, the quantum yield was decreased from 0.80 in cyclohexane to 0.12 in DMSO. The introduction of bulky groups was demonstrated to be effective for suppressing the aggregation effect and thus improving the solid state emission quantum yield. These results indicate that the combined structure modulation strategy offers a powerful tool for tuning the emission behaviour. To demonstrate the possibility of practical applications, 2 was employed as the emitting material for the fabrication of deep-blue organic light-emitting diodes (OLEDs), which showed a maximum external quantum efficiency of 2.2%. The CIE coordinates of (0.15, 0.08) are indicative of excellent blue color purity.
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| 2. |
- Iwnicki, Simon, et al.
(författare)
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Advances in vehicle-track interaction tools
- 2009
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Ingår i: Railway Gazette International. - 0373-5346. ; 165:9, s. 47-52
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- In this article, the authors discuss how computer modeling is enabling researchers to improve their understanding of vehicle-track interaction. This in turn allows for more accurate predictions to be made regarding rail damage on plain lines as well as turn-outs. The authors discuss track interaction models, multi-body system modeling, surface roughness models, and train-turnout interactions. The article concludes with the authors noting that numerous parameters related to design and conditions influence dynamic train-turnout interactions.
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| 3. |
- Li, Xing-Yu, et al.
(författare)
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Comparative Study of Dayside Pulsating Auroras Induced by Ultralow-Frequency Waves
- 2023
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Ingår i: Universe. - : MDPI AG. - 2218-1997. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- Pulsating auroras are usually observed with ultralow-frequency (ULF) waves in the Pc 3-5 band (period 10-600 s). These auroras are thought to result from interactions between energetic electrons and chorus waves, but their relationship with ULF waves remains an open question. In this study, we investigated this question by conducting a comparative study on two ULF wave events with pulsating auroras observed near the magnetic footprints. Conjugate observations from the Magnetospheric Multiscale mission and the Chinese Yellow River Station were used. In both events, lower-band chorus waves were observed, which were suggested to be connected with the auroral pulsations by wavelet analysis. The intensity of these waves oscillates at the period of the ULF waves, but the physics laid behind them differs by events. During the event of 22 January 2019, compressional ULF waves changed the threshold for the whistler anisotropy instability periodically, affecting the emission of chorus waves. In the event on 10 January 2016, poloidal ULF waves modulated the chorus wave generation by regulating electron temperature anisotropy through drift resonance. ULF waves in these events may originate from perturbations in the solar wind. We highlight the role of ULF waves in the solar wind-magnetosphere-ionosphere coupling, which requires further study.
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| 4. |
- Liu, Xiaowan, et al.
(författare)
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Measurements and modelling of dynamic stiffness of a railway vehicle primary suspension element and its use in a structure-borne noise transmission model
- 2021
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- The noise inside railway vehicles is transmitted by both structure-borne and airborne paths and, although there are many sources, the rolling noise is often the most important. This paper focuses on the structure-borne transmission of rolling noise in a metro vehicle. Measurements are presented first of the vertical and lateral dynamic stiffness of a primary suspension element consisting of conical rubber/metal elements. Results are presented for various constant preloads over the frequency range 60600 Hz. An analytical model of the suspension element is also developed, based on a mass-spring system and including wave motion within the rubber elements. The dynamic stiffness results are used in a finite element model of the running gear, consisting of the bogie frame, wheelsets and suspension elements. The excitation is provided by the combined wheel/rail roughness at the contact point. This model is used to calculate the blocked forces at the connection points between the secondary suspension elements and the car body. The blocked forces are combined with measured vibro-acoustic transfer functions from these mounting points to the vehicle interior to determine the structure-borne noise inside the vehicle. The proposed methodology is validated against measurements during operation in terms of acceleration levels, blocked forces and structure-borne noise levels inside the vehicle, showing reasonably good agreement. Including the dynamic stiffness for the primary suspension leads to improved agreement between 100 and 500 Hz compared with using a constant stiffness.
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| 5. |
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| 6. |
- Xie, Zi Kang, et al.
(författare)
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Electron scale coherent structure as micro accelerator in the Earth's magnetosheath
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1, s. 886-
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Tidskriftsartikel (refereegranskat)abstract
- Turbulent energy dissipation is a fundamental process in plasma physics that has not been settled. It is generally believed that the turbulent energy is dissipated at electron scales leading to electron energization in magnetized plasmas. Here, we propose a micro accelerator which could transform electrons from isotropic distribution to trapped, and then to stream (Strahl) distribution. From the MMS observations of an electron-scale coherent structure in the dayside magnetosheath, we identify an electron flux enhancement region in this structure collocated with an increase of magnetic field strength, which is also closely associated with a non-zero parallel electric field. We propose a trapping model considering a field-aligned electric potential together with the mirror force. The results are consistent with the observed electron fluxes from ~50 eV to ~200 eV. It further demonstrates that bidirectional electron jets can be formed by the hourglass-like magnetic configuration of the structure.
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