| 75371. |
- Song, Kai, et al.
(author)
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Constant Current Charging and Maximum System Efficiency Tracking for Wireless Charging Systems Employing Dual-Side Control
- 2020
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In: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 56:1, s. 622-634
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Journal article (peer-reviewed)abstract
- Wireless power transfer (WPT) systems have attracted much attention because of their safety, convenience, and environmental friendliness. For wireless supercapacitor charging, the system efficiency and charging current are highly dependent on the load that varies over a wide range. In this article, a simultaneous maximum system efficiency (MSE) tracking and constant current (CC) charging control scheme for a supercapacitor is proposed. For CC charging, a double-sided LCC topology is chosen due to its characteristic of providing a load-independent output current. Furthermore, the impact of the coil internal resistance on the system characteristics (especially the charging current) is investigated, so a semiactive rectifier is introduced on the secondary side to achieve accurate CC charging and improve the system robustness. Based on the variable-step perturbation and observation algorithm, the MSE is tracked by searching for the minimum system input dc current using a primary-side buck converter on the premise that the charging current reaches its target value. The abovementioned two control loops are independent, and mutual communication is unnecessary when they cooperate; thus, the system is simplified. The simulation and experimental results show great consistency with the theoretical analysis. The experimental system maintains the MSE of 86% during charging the supercapacitor from 20 to 50 V with 2 A.
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| 75372. |
- Song, Minhyup, et al.
(author)
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Compression of ultra-long microwave pulses using programmable microwave photonic phase filtering with > 100 complex-coefficient taps
- 2014
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In: Optics Express. - 1094-4087 .- 1094-4087. ; 22:6, s. 6329-6338
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Journal article (peer-reviewed)abstract
- Microwave photonic filters with arbitrary phase response can be achieved by merging high-repetition-rate electro-optic frequency comb technology with line-by-line pulse shaping. When arranged in an interferometric configuration, the filter features a number of programmable complex-coefficient taps equal to the number of available comb lines. In this work, we use an ultrabroadband comb generator resulting in a microwave photonic phase filter with >100 complex-coefficient taps. We demonstrate the potential of this filter by performing programmable chirp control of ultrawideband waveforms that extend over long (>10 ns) temporal apertures. This work opens new possibilities for compensating realistic linear distortion impairments on ultrabroadband wireless signals spanning over dozens of nanosecond temporal apertures.
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| 75373. |
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| 75374. |
- Song, Peng, et al.
(author)
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Quantum Mechanical study of the coupling of plasmon excitations to atomic scale electron transport
- 2011
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In: The Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:7
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Journal article (peer-reviewed)abstract
- The coupling of optical excitation and electron transport through a sodium atom in a plasmonic dimer junction is investigated using time-dependent density functional theory. The optical absorption and dynamic conductance is determined as a function of gap size. Surface plasmons are found to couple to atomic-scale transport through several different channels including dipolar, multipolar, and charge transfer plasmon modes. These findings provide insight into subnanoscale couplings of plasmons and atoms, a subject of general interest in plasmonics and molecular electronics.
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| 75375. |
- Song, Peng, et al.
(author)
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Quantum plasmonics: Symmetry-dependent plasmon-molecule coupling and quantized photoconductances
- 2012
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In: Physical Review B. - 1098-0121. ; 86:12, s. Article Number: 121410-
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Journal article (peer-reviewed)abstract
- We investigate photoinduced electron transport through nanoparticle dimers connected by linear and ringlike molecules. The two model junctions exhibit similar absorption but distinct photoconductance. The linear-chain junction shows a constant conductance that is independent of photon energies. In contrast, the ring molecules show quantized conductance resonances at energies corresponding to the molecular excitations. These results can be understood from the symmetry and quantization of local molecular excitations, and have implications for plasmon-molecule interactions in general.
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| 75376. |
- Song, T., et al.
(author)
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Self-sustained oscillations in nanoelectromechanical systems induced by Kondo resonance
- 2014
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16
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Journal article (peer-reviewed)abstract
- We investigate the instability and dynamical properties of nanoelectromechanical systems represented by a single-electron device containing movable quantum dots attached to a vibrating cantilever via asymmetric tunnel contacts. The Kondo resonance in electron tunneling between the source and shuttle facilitates self-sustained oscillations originating from the strong coupling of mechanical and electronic/spin degrees of freedom. We analyze a stability diagram for the two-channel Kondo shuttling regime due to limitations given by the electromotive force acting on a moving shuttle, and find that the saturation oscillation amplitude is associated with the retardation effect of the Kondo cloud. The results shed light on possible ways to experimentally realize the Kondo-cloud dynamical probe by using high mechanical dissipation tunability as well as supersensitive detection of mechanical displacement.
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| 75377. |
- Song, T., et al.
(author)
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Shuttle-promoted nano-mechanical current switch
- 2015
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 107:12
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Journal article (peer-reviewed)abstract
- We investigate electron shuttling in three-terminal nanoelectromechanical device built on a movable metallic rod oscillating between two drains. The device shows a double-well shaped electromechanical potential tunable by a source-drain bias voltage. Four stationary regimes controllable by the bias are found for this device: (i) single stable fixed point, (ii) two stable fixed points, (iii) two limit cycles, and (iv) single limit cycle. In the presence of perpendicular magnetic field, the Lorentz force makes possible switching from one electromechanical state to another. The mechanism of tunable transitions between various stable regimes based on the interplay between voltage controlled electromechanical instability and magnetically controlled switching is suggested. The switching phenomenon is implemented for achieving both a reliable active current switch and sensoring of small variations of magnetic field.
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| 75378. |
- Song, Yang, et al.
(author)
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Affective flows and inequalities of international students’ intercultural communication in the digital era: A Sino-Swedish comparative study
- 2023
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Conference paper (other academic/artistic)abstract
- The COVID-19 pandemic has given rise to the wide adoption of online teaching and draws attention to students’ digital literacies and intercultural competence online. Nevertheless, there is a sheer paucity of research on how international students’ intercultural experiences are shaped by their digital practices. Given the distinct digital and linguistic environments in China and Sweden, this study focuses on the two-way flow of international students between Anglo-European countries and China and aims to investigate the affective dimension of their intercultural experiences in the digital era. Drawing on Deleuzian and Guattarian theory of affect (Deleuz & Guattari 1987/2004), we define affective flows as the socio-emotional condition of intercultural communication provisioned by structural and contingent assemblages of human, non-human, and material-semiotic resources. We conducted semi-structured interviews with a total of 12 international students enrolled in English-medium-instruction master’s degree programs, 6 at a Chinese university and 6 at a Swedish university. The participants were also invited to draw out media diagrams and share anonymized social media interaction episodes. The triangulated data analysis reveals that international students in both universities have experienced diverse socio-emotions while being embedded in affective flows at the online-offline nexus. International students have, in general, reported positive emotions by strategically using emojis, memes, stickers, short videos, and linguistics resources to navigate and coordinate multiple social media platforms to maintain social bonding with families, classmates, friends, and professionals across time and space. Meanwhile, affective inequalities exist within and between the two distinct cohorts of international students and are shaped by interacting forces, which are historical, politico-economic, and material-technological. The unequal accessibility to institutional, communal, and linguistic resources also played salient roles in creating individual-specific, emotional challenges in intercultural communication. Practical suggestions are made to incorporate digital intercultural communication education in implementing international EMI programs worldwide.
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| 75379. |
- Song, Yujiao, 1986, et al.
(author)
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Analytical investigation of poorly damped conditions in VSC-HVDC systems
- 2016
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In: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - 9781509018376 ; , s. Art no 7798762, Pages 3279-3285
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Conference paper (peer-reviewed)abstract
- In this paper, strong AC-grid connected VSC-HVDC systems are studied. Under specific conditions, such systems can suffer from both stability and poor damping related issues, which warrants a stability study. Analytical eigenvalue expressions can directly demonstrate the impact of physical or control parameters on the system stability. However, especially in case of high-order systems, such expressions are challenging to obtain. This paper suggests a method to symbolically represent approximative eigenvalues of two-terminal VSC-HVDC systems, which could also be used to analyze the system dynamics. In addition, by applying symbolic-isolation method, the order of a multi-terminal VSC-HVDC system canbe reduced to an equivalent two-terminal VSC-HVDC system,which enables the proposed method to provide symbolic pole expressions. Numerical studies based on Matlab simulations are presented, showing the accuracy of the analytical eigenvalue expressions and providing useful hints on the impact of physical or control parameters.
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| 75380. |
- Song, Yuxin, 1981, et al.
(author)
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Dilute Bismides for Mid-IR Applications
- 2013
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In: Springer Series in Materials Science. - New York, NY : Springer New York. - 2196-2812 .- 0933-033X. - 9781461481218 ; 186, s. 1-27
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Book chapter (other academic/artistic)abstract
- Dilute bismides are a group of emerging materials with unique properties. Incorporation of a small amount of Bi in common III–V host materials results in large band-gap reduction and strong spin-orbit splitting, leading to potential applications in mid-infrared (Mid-IR) optoelectronics. In this chapter, we review recent progresses on epitaxy and characterizations of novel bismides, i.e., GaSb1−x Bi x , InSb1 − x Bi x , InAs1 − x Bi x , and InAsSbBi. Although these dilute bismides have been successfully grown, to obtain high Bi incorporations and retain high crystal quality is still very challenging.
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