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Statistical analysis and interpretation on lightning impulse breakdown voltages of ester liquids under varying field uniformity

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High Voltage 2024年第1期9卷 22-34页

作者： Haichuan Yu Qiang Liu Zhongdong Wang Department of Electrical and Electronic Engineering The University of ManchesterManchesterUK Department of Engineering University of ExeterExeterUK

Ester liquids(ELs),as the alternative transformer liquids to the conventional mineral oils(MOs),have been increasingly used in power transformers with high voltage *** various properties,the lightning impulse breakdown voltages(LIBDVs)have been studied elaborately in the past two decades under different electric field *** electric field uniformities do have an effect on the breakdown characteristics,for example,breakdown mechanisms,polarity effects,and differences of LIBDV between ELs and MOs,which is quantitatively investigated based on the LIBDVs collected from the *** breakdown mechanism transition phenomenon between streamer initiation dominated breakdown and streamer propagation dominated breakdown has been reviewed ***,the transition field factor boundaries to observe the polarity effect on LIBDVs are taken at around 20 for ELs and 10 for ***,the transition field factor boundaries to observe the LIBDV distinctions between ELs and MOs are about 109 and 14 under positive and negative lightning impulse,*** systematic analysis and interpretation on the transition field factor boundaries among different phenomena can provide insights on insulation design of ELs filled power transformers.

关键词： field lightning breakdown

Controlling the properties of surface acoustic waves using graphene

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Nano Research 2016年第3期9卷 685-691页

作者： Lokeshwar Bandhu Geoffrey R. Nash College of Engineering Mathematics and Physical Sciences University of Exeter Exeter EX4 4QF UK

Surface acoustic waves （SAWs） are elastic waves that propagate on the surface of a solid, much like waves on the ocean, with SAW devices used widely in communication and sensing. The ability to dynamically control the properties of SAWs would allow the creation of devices with improved performance or new functionality. However, so far it has proved extremely difficult to develop a practical way of achieving this control. In this paper we demonstrate voltage control of SAWs in a hybrid graphene-lithium niobate device. The velocity shift of the SAWs was measured as the conductivity of the graphene was modulated using an ion-gel gate, with a 0.1% velocity shift achieved for a bias of approximately 1 V. This velocity shift is comparable to that previously achieved in much more complicated hybrid semiconductor devices, and optimization of this approach could therefore lead to a practical, cost-effective voltage-controlled velocity shifter. In addition, the piezoelectric fields associated with the SAW can also be used to trap and transport the charge carriers within the graphene. Uniquely to graphene, we show that the acoustoelectric current in the same device can be reversed, and switched off, using the gate voltage.

关键词： graphene sensors surface acoustic wave charge transport

Metamaterial-based graphene thermal emitter

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Nano Research 2018年第7期11卷 3567-3573页

作者： Cheng Shi Nathan H. Mahlmeister Isaac J. Luxmoore Geoffrey R. Nash College of Engineering Mathematics and PhysicaI Sciences University of Exeter Exeter EX4 4QF UK

A thermal emitter composed of a frequency-selective surface metamaterial layer and a hexagonal boron nitride-encapsulated graphene filament is demonstrated. The broadband thermal emission of the metamaterial （consisting of ring resonators） was tailored into two discrete bands, and the measured reflection and emission spectra agreed well with the simulation results. The high modulation frequencies that can be obtained in these devices, coupled with their operation in air, confirm their feasibility for use in applications such as gas sensing.

关键词： graphene hexagonal boron nitride thermal emitter infrared metamaterial

Mechanical behavior predictions of additively manufactured microstructures using functional Gaussian process surrogates

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npj Computational Materials 2021年第1期7卷 720-730页

作者： Robert Saunders Celia Butler John Michopoulos Dimitris Lagoudas Alaa Elwany Amit Bagchi US Naval Research Laboratory WashingtonDCUSA Texas A&M university College StationTXUSA Synopsys Northern Europe Ltd ExeterUK university of exeter ExeterUK

Relational linkages connecting process,structure,and properties are some of the most sought after goals in additive manufacturing(AM).This is desired especially because the microstructural grain morphologies of AM components can be vastly different than their conventionally manufactured ***,data collection at the microscale is ***,this work describes and demonstrates a methodology to link microstructure morphology to mechanical properties using functional Gaussian process surrogate models in a directed graphical network capable of achieving near real-time property predictions with single digit error magnitudes when predicting full stress–strain histories of a given *** methodology is presented and demonstrated using computationally generated microstructures and results from crystal plasticity simulations on those *** surrogate model uses grain-level microstructural descriptors rather than whole microstructure descriptors so that properties of new,arbitrary microstructures can be *** developed network has the potential to scale to predict mechanical properties of grain structures that would be infeasible to simulate using finite element methods.

关键词： grain microstructure additive

A Transnational Witness to ＂Other＂ Stories of Suffering： Encountering Czech Memory in Selected Works by the French Novelist Sylvie Germain

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Fudan Journal of the Humanities and Social Sciences 2016年第2期9卷 253-288页

作者： Clare Horackova university of exeter Exeter UK

The French novelist Sylvie Germain spent 6 years in Czechoslovakia before, during, and after the Velvet Revolution of 1989 that ended four decades of oppressive totalitarian rule in that country. As a result of her stay, Germain produced four texts that are imbued with painful Czech stories and memories of both the Holocaust and the Communist era. This study examines the inscription of Germain＇ s encounter with the （Czech） other into her writing through tropes of exile and dispossession, of the suffering or wounded body, and of illness. Although Germain did not experience either the Holocaust or totalitarianism at first hand, and has moreover no claim to a Czech heritage, I posit that her work can nonetheless be interpreted as a transnational witness to the suffering of the （Czech） other. Using theories of the self and other, as well as theories of exile and of the narration of illness, I discuss how Germain＇s work negotiates the fine line between an appropriation of the stories of the other and an ethical responsibility to respond to other stories of pain.

关键词： Sylvie Germain Contemporary French literature Transnationalwitnessing Illness narratives The body

A viscoelastic nonlinear energy sink with an electromagnetic energy harvester:Narrow-band random response

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Chinese Physics B 2024年第7期33卷 147-156页

作者：廖志晶孙亚辉刘洋 School of Mathematics and Statistics Guangdong University of TechnologyGuangzhou 510520China exeter Small-Scale Robotics Laboratory Engineering DepartmentUniversity of ExeterNorth Park RoadExeter EX44QFUK

Nonlinear energy sink is a passive energy absorption device that surpasses linear dampers, and has gained significant attention in various fields of vibration suppression. This is owing to its capacity to offer high vibration attenuation and robustness across a wide frequency spectrum. Energy harvester is a device employed to convert kinetic energy into usable electric energy. In this paper, we propose an electromagnetic energy harvester enhanced viscoelastic nonlinear energy sink(VNES) to achieve passive vibration suppression and energy harvesting simultaneously. A critical departure from prior studies is the investigation of the stochastic P-bifurcation of the electromechanically coupled VNES system under narrowband random excitation. Initially, approximate analytical solutions are derived using a combination of a multiple-scale method and a perturbation approach. The substantial agreement between theoretical analysis solutions and numerical solutions obtained from Monte Carlo simulation underscores the method's high degree of validity. Furthermore, the effects of system parameters on system responses are carefully examined. Additionally, we demonstrate that stochastic P-bifurcation can be induced by system parameters, which is further verified by the steady-state density functions of displacement. Lastly,we analyze the impacts of various parameters on the mean square current and the mean output power, which are crucial for selecting suitable parameters to enhance the energy harvesting performance.

关键词： nonlinear energy sink fractional-order damping multiple-scale method energy harvester

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Preparation of 3D graphene-based architectures and their applications in supercapacitors

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Progress in Natural Science:Materials International 2015年第6期25卷 554-562页

作者： Zhuxian Yang Sakineh Chabi Yongde Xia Yanqiu Zhu College of Engineering Mathematics and Physical SciencesUniversity of Exeter

Three dimensional(3D) graphene-based architectures such as 3D graphene-based hydrogels,aerogels,foams,and sponges have attracted huge attention owing to the combination of the structural interconnectivities and the outstanding properties of graphene which offer these interesting structures with low density,high porosity,large surface area,stable mechanical properties,fast mass and electron *** have been extensively studied for a wide range of applications including capacitors,batteries,sensors,catalyst,*** are several reviews focusing on the 3D graphene-based architectures and their *** this work,we only summarise the latest development on the preparation of 3D graphene-based architectures and their applications in supercapacitors,with emphasis on the preparation strategies.

关键词： 3D-graphene Supercapacitor Electrode architecture

Olfaction alters spatial memory strategy of scatter-hoarding animals

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Integrative Zoology 2021年第1期16卷 128-135页

作者： Sijie YI Minghui WANG Mengyao JU Xianfeng YI College of Life and Environmental Sciences University of ExeterExeterUK College of Life Sciences Qufu Normal UniversityQufuChina

Although it has been suggested that olfaction is closely interconnected with hippocampal systems,whether olfaction regulates spatial memory strategy remains never ***,no study has examined how olfaction mediates spatial memory established on the external objects,for example,caches made by scatter-hoarding ***,we experimentally induced nondestructive and reversible olfaction loss of a scatter-hoarding animal Leopoldamys edwardsi,to test whether and how olfaction regulates spatial memory to mediate cache recovery and *** results showed that the normal *** preferred to pilfer caches of others rather than to recover their own using accurate spatial memory(35.7%vs.18.6%).Anosmic *** preferred to recover the caches they made prior to olfaction loss rather than to pilfer from others relied on spatial memory(54.2%vs.36.0%).However,*** with anosmia showed no preference either to the caches they established after olfaction loss or caches made by others(25.8%vs.29.1%).These collectively indicate that olfaction loss has a potential to affect new memory formation but not previously established spatial memory on *** study first showed that olfaction modified spatial memory strategy in cache recovery and pilferage behaviors of scatter-hoarding *** suggest that future studies pay more attention to the evolution of olfaction and its relationship with spatial memory strategy.

关键词： cache pilferage cache recovery olfaction scatter-hoarding spatial memory

Strength properties of xanthan gum and guar gum treated kaolin at different water contents

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第5期13卷 1160-1172页

作者： Irem Bozyigit Akbar Javadi Selim Altun Department of Civil Engineering Ege UniversityBornova-IzmirTurkey College of Engineering Mathematics and Physical SciencesUniversity of ExeterExeterUK

Nowadays,using biopolymer as a ground improvement method has become very ***,since biopolymers are organic and degradable,their long-term effect is not fully *** this study,the effects of biopolymers on the mechanical behavior of kaolin clay were investigated through a comprehensive program of *** types of biopolymer,*** gum and guar gum were chosen to investigate the effect of biopolymer *** this purpose,specimens were prepared using standard Proctor energy at four different water contents(25%,30%35%and 40%)with 0.5%,1%,1.5%and 2%biopolymer *** specimens were cured for 1 d,7 d,28 d and 90 ***,some of the specimens were kept in the curing room for 3 years to observe the long-term effect of the *** the end of the curing periods,the specimens were subjected to unconfined compression test,and scanning electron microscopy(SEM)analysis was performed to observe the mechanism of strength *** results revealed that the unconfined compressive strength(UCS)of the specimens treated with biopolymers increased in all biopolymer inclusion levels and water contents up to a 90-d curing *** specimens containing xanthan gum,the maximum strength increase was observed at 25%water content and 2%xanthan gum with 90-d *** strength increased 5.23 times induced by xanthan gum addition when compared to the pure ***,the increase in strength reached 8.53 times in specimens treated with guar ***,increasing water content caused more ductile behavior,thus increasing the axial deformation.

关键词： Biopolymer Clay Unconfined compressive strength(UCS) Xanthan gum Guar gum Strength properties

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