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state Transition Induced by self-steepening and self Phase-Modulation

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Chinese Physics Letters 2014年第1期31卷 33-36页

作者： He Jing-song Xu shu-Wei M. s. Ruderman R. Erdélyi Department of Mathematics Ningbo University Ningbo 315211 DAMTP University of Cambridge Cambridge CB3 0WA UK school of Mathematics University of Science and Technology of China Hefei 230026 solar Physics and space Plasma Research Centre University of Sheffield Sheffield S3 7RH UK

We present a rational solution for a mixed nonlinear schr6dinger （MNLs） equation. This solution has two free parameters, a and b, representing the contributions of self-steepening and self phase-modulation （sPM） of an associated physical system, respectively. It describes five soliton states： a paired bright-bright soliton, a single soliton, a paired bright-grey soliton, a paired bright-black soliton, and a rogue wave state. We show that the transition among these live states is induced by self-steepening and sPM through tuning the values of a and b. This is a unique and potentially fundamentally important phenomenon in a physical system described by the MNLs eauation.

关键词： solitons

sIMULTANEOUs sAXs/WAXs/DsC sTUDIEs ON MICROsTRUCTURE OF CONVENTIONAL AND METALLOCENE-BAsED ETHYLENE-BUTENE COPOLYMERs

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Chinese Journal of Polymer science 2004年第3期22卷 279-287页

作者：徐君庭 Anthony J. Ryan Department of Polymer science & Engineering Zhejiang University Hangzhou 310027 China Chemistry Department The University of Sheffield Sheffield S3 7HF UK

The fractions of one metallocene-based (mPE) and one conventional (znPE) ethylene-butene copolymer eluted at from temperature rising elution fractionation were selected for DsC and time-resolved small angle X-ray scattering (sAXs) and wide angle X-ray scattering (WAXs) characterization. The DsC and WAXs results show that two crystal structures exist in both mPE and znPE: structure A with higher melting temperature and structure B with lower melting temperature. It was found that original znPE (s-znPE) contains more highly ordered structure A than original mPE (s-mPE) in spite of the higher comonomer content of znPE. Another structure C is also identified because of higher crystallinity measured by WAXs than by DsC and is attributed to the interfacial region. The sAXs data were analyzed with correlation function and two maxima were observed in s-mPE and s-znPE, in agreement with the conclusion of two crystal populations drawn from DsC and WAXs results. These two crystal populations have close long periods in s-mPE, but very different long periods in s-znPE. In contrast, freshly crystallized mPE and znPE (f-mPE and f-znPE) contain only a single crystal population with a broader distribution of long period

关键词： sAXs WAXs Microstructure Metallocene Ethylene-butene copolymer

Regulating the morphology of fluorinated non-fullerene acceptor and polymer donor via binary solvent mixture for high efficiency polymer solar cells

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science China Chemistry 2019年第9期62卷 1221-1229页

作者： Mengxue Chen Zhuohan Zhang Wei Li Jinlong Cai Jiangsheng Yu Emma L. K. spooner Rachel C. Kilbride Donghui Li Baocai Du Robert s. Gurney Dan Liu Weihua Tang David G. Lidzey Tao Wang school of Materials science and Engineering Wuhan University of Technology Wuhan 430070 China state Key Laboratory of silicate Materials for Architectures Wuhan University of Technology Wuhan 430070 China school of Chemical Engineering Nanjing University of Science and Technology Nanjing 210094 China Department of Physics and Astronomy University of Sheffield Sheffield S3 7RH UK

Fluorinated non-fullerene acceptors(NFAs) usually have planar backbone and a higher tendency to crystallize compared to their non-fluorinated counterparts, which leads to enhanced charge mobility in organic solar cells(OsCs). However, this selforganization behavior may result in excessive phase separation with electron donors and thereby deteriorate device ***, we demonstrate an effective approach to tune the molecular organization of a fluorinated NFA(INPIC-4 F), and its phase separation with the donor PBDB-T, by varying the casting solvent. A prolonged film drying time encourages the crystallization of INPIC-4 F into spherulites and consequently results in excessive phase separation, leading to a low device power conversion efficiency(PCE) of 8.1%. Contrarily, a drying time leads to fine mixed domains with inefficient charge transport properties,resulting in a moderate device PCE of 11.4%. An intermediate film drying time results in the formation of face-on π-π stacked PBDB-T and INPIC-4 F domains with continuous phase-separated networks, which facilitates light absorption, exciton dissociation as well as balanced charge transport towards the electrode, and achieves a remarkable PCE of 13.1%. This work provides a rational guide for optimizing the molecular ordering of NFAs and electron donors for high device efficiency.

关键词： organic solar cells non-fullerene acceptors solvent morphology efficiency

The Long-term survival Chances of Young Massive star Clusters

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Chinese Journal of Astronomy and Astrophysics 2007年第2期7卷 155-186页

作者： Richard de Grijs Geneviève Parmentier Department of Physics & Astronomy The University of Sheffield Hicks Building Hounsfield Road Sheffield S3 7RH U. K.National Astronomical Observatories Chinese Academy of SciencesBeijing 100012 Institute of Astrophysics & Geophysics Université de LiègeAllée du 6 Aot17Sart-Tilman (B5c)B-4000 LiègeBelgium

We review the long-term survival chances of young massive star clusters （YMCs）, hallmarks of intense starburst episodes often associated with Violent galaxy interactions. We address the key question as to whether at least some of these YMCs can be considered protoglobular clusters （GCs）, in which case these would be expected to evolve into counterparts of the ubiquitous old GCs believed to be among the oldest galactic building blocks. In the absence of significant external perturbations, the key factor determining a cluster＇s long-term survival chances is the shape of its stellar initial mass function （IMF）. It is, however, not straightforward to assess the IMF shape in unresolved extragalactic YMCs. We discuss in detail the promise of using high-resolution spectroscopy to make progress towards this goal, as well as the numerous pitfalls associated with this approach. We also discuss the latest progress in worldwide efforts to better understand the evolution of entire cluster systems, the disruption processes they are affected by, and whether we can use recently gained insights to determine the nature of at least some of the YMCs observed in extragalactic starbursts as proto-GCs. We conclude that there is an increasing body of evidence that GC formation appears to be continuing until today; their long-term evolution crucially depends on their environmental conditions, however.

关键词： stellar dynamics - globular clusters general - galaxies interactions - Magellanic Clouds - galaxies starburst - galaxies star clusters

Tuning the translational freedom of DNA for high speed AFM

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Nano Research 2015年第6期8卷 1811-1821页

作者： Andrew J. Lee Michal szymonik Jamie K. Hobbs Christoph Walti Bioelectronics School of Electronic and Electrical Engineering University of Leeds Leeds LS2 9JT UK Department of Physics and Astronomy University of Sheffield Sheffield 53 7RH UK

Direct observation is arguably the preferred way to investigate the interactions between two molecular complexes. With the development of high speed atomic force microscopy （AFM）, it is becoming possible to observe directly DNA-protein interactions with relevant spatial and temporal resolutions. These interactions are of central importance to biology, bionanotechnology, and functional biologically inspired materials. As in all microscopy studies, sample preparation plays a central role in AFM observation and minimal perturbation of the sample is desired. Here, we demonstrate the ability to tune the interactions between DNA molecules and the surface to create an association strong enough to enable high-resolution AFM imaging while also providing sufficient translational freedom to allow the relevant protein-DNA interactions to take place. Furthermore, we describe a quantitative method for measuring DNA mobility, while also determining the individual forces contributing to DNA movement. We found that for a weak surface association, a significant contribution to the movement arises from the interaction of the AFM tip with the DNA. In combination, these methods enable the tuning of the surface translational freedom of DNA molecules to allow the direct study of a wide range of nucleo-protein interactions by high speed atomic force microscopy.

关键词： high speed atomic forcemicroscopy (Hs-AFM) DNA protein bionanotechnology

Novel switched Flux Permanent Magnet Machine Topologies

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电工技术学报 2012年第7期27卷 1-16页

作者：诸自强 University of sheffield sheffield s1 3JD UK

This paper overviews various switched flux permanent magnet machines and their design and performance features,with particular emphasis on machine topologies with reduced magnet usage or without using magnet,as well a... 详细信息

关键词：电工技术电力科学技术教育电力学

Discrete simulation of Flexible Plate structure Using state-space Formulation

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系统仿真学报 2008年第19期20卷 5141-5146页

作者： s. Md. salleh M. O. Tokhi Department of Automatic Control and system Engineering The University of Sheffield Sheffield S3 1JD U. Kingdom Faeulty of Mechanical and Manufacturing Engineering University of Tun Hussein Onn Malaysia 86400 Johor Malaysia

This paper presents the development of dynamic simulation of a flexible plate structure with various boundary conditions. A flexible square plate is considered. A finite-difference method is used to discretise the governing partial differential equation formulation describing its dynamic behaviour. The model thus developed has been validated against characteristic parameters of the plate. The model thus developed is further formulated using discrete state-space representation, to allow easy and fast implementation for simulating the dynamic behaviour of the plate with various boundary conditions. The simulation algorithm thus developed is validated, and accurate results with representation of the first five modes of vibration of the plate have been achieved. The algorithm thus developed is used in subsequent research work as a platform for development and verification of suitable control strategies for vibration suppression of flexible plate structures.

关键词：复杂系统模拟技术平面结构分析方法系统结构

Machine learning models for the secondary Bjerknes force between two insonated bubbles

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Acta Mechanica sinica 2021年第1期37卷 35-46,I0001页

作者： Haiyan Chen Yue Zeng Yi Li school of Material and Energy Guangdong University of TechnologyGuangzhou510006China school of Mathematics and statistics University of SheffieldSheffieldS37RHUK

The secondary Bjerknes force plays a significant role in the evolution of bubble ***,due to the complex dependence of the force on multiple parameters,it is highly non-trivial to include its effects in the simulations of bubble *** this paper,machine learning is used to develop a data-driven model for the secondary Bjerknes force between two insonated bubbles as a function of the equilibrium radii of the bubbles,the distance between the bubbles,the amplitude and the center frequency of the ultrasound *** sign of the force may change with the phase difference between the oscillating ***,the magnitude of the force varies over several orders of magnitude,which poses a serious challenge for the usual machine learning *** overcome this difficulty,the magnitudes and the signs of the force are separated and modelled separately.A nonlinear regression is obtained with a feed-forward network model for the logarithm of the magnitude,whereas the sign is modelled by a support-vector machine *** principle,the practical aspects related to the training and validation of the machine models are *** predictions from the models are checked against the values computed from the Keller-Miksis *** results show that the models are extremely efficient while providing accurate estimate of the *** models make it computationally feasible for the future simulations of the bubble clusters to include the effects of the secondary Bjerknes force.

关键词： Bubble clusters secondary Bjerknes force Machine learning Neural networks support-vector machine Numerical simulations

Observation of Zitterbewegung in photonic microcavities

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Light(science & Applications) 2023年第6期12卷 1084-1090页

作者： seth Lovett Paul M.Walker Alexey Osipov Alexey Yulin Pooja Uday Naik Charles E.Whittaker Ivan A.shelykh Maurice s.skolnick Dmitry N.Krizhanovskii Department of Physics and Astronomy University of SheffieldS37RH SheffieldUK Department of Physics and Technology ITMO UniversitySt.Petersburg 197101Russia science Institute University of IcelandDunhagi 3IS-107 ReykjavikIceland

We present and experimentally study the effects of the photonic spin–orbit coupling on the real space propagation of polariton wavepackets in planar semiconductor microcavities and polaritonic analogues of *** particular,we demonstrate the appearance of an analogue Zitterbewegung effect,a term which translates as‘trembling motion’in English,which was originally proposed for relativistic Dirac electrons and consisted of the oscillations of the centre of mass of a wavepacket in the direction perpendicular to its *** a planar microcavity,we observe regular Zitterbewegung oscillations whose amplitude and period depend on the wavevector of the *** then extend these results to a honeycomb lattice of coupled microcavity *** to the planar cavity,such lattices are inherently more tuneable and versatile,allowing simulation of the Hamiltonians of a wide range of important physical *** observe an oscillation pattern related to the presence of the spin-split Dirac cones in the *** both cases,the experimentally observed oscillations are in good agreement with theoretical modelling and independently measured bandstructure parameters,providing strong evidence for the observation of Zitterbewegung.

关键词： planar versatile analogues