Accedi

Bibliografie tematiche / Tunnelling / Tesi

Tesi sul tema "Tunnelling"

Segui questo link per vedere altri tipi di pubblicazioni sul tema: Tunnelling.

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 28 luglio 2024

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Tunnelling".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.

1

Coombs, J. H. "Scanning tunnelling microscopy : design and tunnelling characteristics". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233725.

Testo completo

Abstract (sommario):

Scanning Tunnelling Microscopy (STM) is a newly developed technique providing, for the first time, atomic resolution images of conducting surfaces. In its short lifetime it has not only solved a number of long standing surface science problems, for instance simultaneously elucidating both the atomic and electronic structure of the Si(lll) surface, but also earned its inventors, G.Binnig and H.Rohrer, the Nobel Prize. This dissertation describes the construction of one of the earliest STMs and its continued development into a generally available machine. This design differs significantly from that of Binnig and Rohrer both in terms of the all important vibration isolation techniques used and the mechanics of the STM itself. There are now a number of machines built along these lines elsewhere. One of the advantages of this approach is the comparative ease with which it can be modified to operate at low temperatures, and a cryogenic STM running in Ultra High Vacuum has been built The STM operates by holding a sharp metal point (the 'tip') sufficiently close to the surface under investigation that electrons may tunnel directly from one metal to the other. Observation of the tunnel current/separation relationship whilst the tip is scanned in a raster pattern across the surface provides the information from which the images are formed. The tunnelling process itself is of considerable interest, and theory and data are presented relating to the low voltage parabolic conductance, the effect of the image potential on tunnelling and the effect of tip curvature at high applied voltages. During this investigation a number of surfaces have been studied, and atomic resolution images of Pt(llO), Si (100) and graphite are presented. Moreover, images of local molecular ordering in a Langmuir-Blodgett monolayer have been obtained, as well as data showing the effect of protein molecules. These exemplify the surprising range of applications of this technique.

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Lawunmi, David Laditi. "Theoretical studies of scanning tunnelling microscopy and tunnelling phenomena". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386087.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Leane, Robert B. "Scanning tunnelling microscopy". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291716.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Martin, Patrick Michael. "Magnetospectroscopy of electron and hole tunnelling in (AlGa) as resonant tunnelling structures". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363614.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Reddick, William Michael. "Novel silicon tunnelling devices". Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/251612.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Speakman, Alison. "Studies of tunnelling barriers". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239086.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Ko, D. Y. K. "Quantum tunnelling in heterostructures". Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384673.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Leadbeater, Mark Levence. "Resonant tunnelling in semiconductor heterostructures". Thesis, University of Nottingham, 1990. http://eprints.nottingham.ac.uk/28733/.

Testo completo

Abstract (sommario):

This thesis examines the electrical transport properties of a series of n-type GaAs/(AIGa)As double barrier resonant tunnelling devices with well widths between 50 angstrem and 2400 angstrem . The current-voltage characteristics show peak-to-valley ratios as high as 25:1 and as many as seventy resonances, with clear evidence of quantum interference effects at room temperature. The application of a high magnetic field parallel to the current flow produces magnetooscillations in the transport properties which allow the sheet charge density in the accumulation layer to be determined. The energy level in the well over a wide range of bias is obtained from analysis of thermal activation of resonant tunnelling. The contributions of elastic scattering and LO phonon emission to the valley current are investigated spectroscopically with a magnetic field and two phonon modes of the (AIGa)As barrier are observed. The buildup of space charge in the quantum well at resonance leads to intrinsic bistability in the current and differential capacitance of an asymmetric structure. Magnetoquantum oscillations due to a degenerate electron gas in the well are used to measure this charge buildup and demonstrate that the tunnelling process is truly sequential. The bistability is dramatically enhanced at high magnetic fields when the lowest energy Landau level of the well can accommodate a high electron density. In a strongly asymmetric sample, a new kind of bistability is observed where the off-resonant current exceeds the resonant current due to enhancement of charge buildup by intersubband scattering. The modulation of the scattering rate by a magnetic field produces periodic oscillations in the width of the bistability. In a magnetic field applied perpendicular to the current, the resonances are broadened as a consequence of the conservation of canonical momentum. The transition from electric to magnetic quantisation in wide wells is investigated and tunnelling into interfacial Landau levels is observed. The angular dependence of the resonances is used to probe conduction band anisotropy. In a tilted field, a completely new type of magneto-oscillations is observed.

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Hill, Richard John Allan. "Tunnelling into InAs quantum dots". Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/10002/.

Testo completo

Abstract (sommario):

This thesis describes an experimental study of the electronic properties of semiconductor heterostructure tunnel devices. InAs self-assembled quantum dots (QDs) are incorporated into the barrier layer of a GaAs/AlAs/GaAs tunnel diode. When a voltage, V, is applied across the device, we observe resonant features in the tunnel current, I, whenever an electron state in one of the qds comes into resonance with an occupied electron state in the emitter. We employ an electron state of a single qd as a spectroscopic probe of a two-dimensional electron system (2DES), from the Fermi energy to the subband edge [1]. For magnetic field B applied parallel to the current, we observe peaks in the I(V) characteristics corresponding to the formation of Landau levels in the 2DES. We obtain quantitative information about the energy dependence of the quasiparticle lifetime, Tqp, of the 2DES. We find that Tqp ~ 2.5 hbar=(Ef - E), in contrast with the expectation for a normal Fermi liquid, but in agreement with predictions for a Fermi liquid state of a disordered 2DES. Close to filling factor nu = 1 we observe directly the exchange enhancement of the g factor. This thesis also describes the design, realisation and measurement of a tunnel diode incorporating InAs QDs and a series of 4 planar electrostatic gates. By applying a bias to the gates, it is possible to selectively inject current into a particular QD. We use magneto-tunnelling spectroscopy to determine the energy levels of the ground and excited state of a single QD, and to map the spatial form of the wave functions of these states [2]. The effect of pressure on the resonant tunnelling of the QDs is also described. [1] P. C. Main et al., Phys. Rev. Lett. 84, 729 (2000) [2] R. J. A. Hill et al., Appl. Phys. Lett. 79, 3275 (2001)

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Puygranier, B. A. F. "The photon scanning tunnelling microscope". Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368568.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Muraki, Yoshinao. "The umbrella method in tunnelling". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10740.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Tewordt, Matthias Ludwig. "Resonant tunnelling in quantum dots". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260415.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Cooper, Michael Lloyd. "Tunnel-induced ground movements and their effects on existing tunnels and tunnel linings". Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289380.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Wai, Man-hon John. "Mixed face tunnelling in Hong Kong /". View the Table of Contents & Abstract, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36762817.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Hutchinson, A. "Acoustoelectric interactions in resonant tunnelling structures". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604843.

Testo completo

Abstract (sommario):

This thesis presents a novel device architecture allowing the monolithic integration of SAWs and semiconductors, which compensates for the inherent weakness of piezoelectric coupling in GaAs by relying on a strong non-local interaction mechanism. A special double-barrier quantum well RTS is designed so that large vertical currents can be sensitivity triggered by a small potential near the surface of the structure, such as the potential associated with a SAW. When a SAW beam is incident on the RTS mesa, the peaks ( and valleys) of the SAW electric field change the potential across the quantum well, resulting in local increases (and decreases) of the current through the structure. With the appropriate device design, the net effect of the SAW integrated over the entire RTS mesa will induce a microwave current in the receiving circuit connected to the RTS emitter. The basic linear and nonlinear properties of the microwave response have been investigated. Simple phenomenological models taking into account the spatial distribution of the SAW electric field and the nonlocality of the RTS conductivity have demonstrated good agreement with experimental results. The effect of varying the RTS layer structure on both the dc characteristics and the microwave response has been investigated theoretically, and experiments once again support the predictions. A process for non-annealed Ohmic contact to the RTS emitter has been optimized, in which Al is grown in situ on highly-doped GaAs incorporating several layers of δ-doping near the surface. The use of this contact method helps to eliminate the extrinsic instability observed in the negative differential resistance region of early devices. Finally, possible applications of the interaction are discussed, including a proposal for the parametric generation of very high frequency SAWs.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Wai, Man-hon John, e 韋文瀚. "Mixed face tunnelling in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45014334.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Eide, Leon Nikolay Røren. "TBM Tunnelling at the Stillwater Mine". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26998.

Testo completo

Abstract (sommario):

When considering the use of TBM as an alternative to conventional Drill & Blast tunnelling, it is of great importance to be able to give thorough and realistic performance predictions. Errors in prediction could be fatal for hard rock TBM projects, as these have a high geological risk and also demands high investment costs. This thesis is meant to provide field data to be used in the work of updating the NTNU prediction model. The effect of RPM on the rock breaking and TBM performance, as well as the effect of the rock mass fracturing have in particular been investigated. As a final purpose of this thesis laboratory testing has been performed to find the Drilling Rate Index™ and the Cutter Life Index™ of rock material. The field study of this thesis has been done at the Stillwater Mine in Montana, USA.The findings of the RPM trials conducted seem to support the notion that running the TBM at a lower RPM gives a higher basic penetration in millimeter per cutterhead revolution, and that the rock breaking process is more efficient. The effect on the rock breaking process may be explained by how the loading rate between cutter and rock surface is influenced by the speed the cutterhead rotates with. Through analyzing shift logs from the TBM in areas of high rock fracturing it has also been found that lowering the RPM will give a higher basic penetration. In this case it is however not certain if this is due to how the rock break off the surface, or if it is caused by the fact that the penetration rate in areas of high rock fracturing is limited by the muck removal capacity of the TBM conveyor. Through analysis of collected core sample data from probe drilling ahead of the TBM, it has been found that the rock mass fracturing has a strong correlation with the TBM penetration rate. It was also found that the rock mass fracturing highly influences the applicable thrust force of the TBM and thusly also has an indirect effect on the TBM performance. More work should be done at the Stillwater Mine regarding geological back mapping of the tunnel, in order to further assess the importance of the rock mass fracturing factor ks.A full laboratory testing of rock samples from the tunnel at the Stillwater Mine has been performed. Rock material in the form of both rock chips from the tunnel face and core samples from probe drilling have been tested. It was in the course of this testing observed that the Sievers' J test results are greatly different in rock chips compared with core samples. This is most likely caused by difference in mineralogy in the samples, and the fact that rock chips contain micro fractures from the rock breaking process. More work on assessing this difference should nonetheless be done.

Gli stili APA, Harvard, Vancouver, ISO e altri

18

McDonnell, Paul. "Resonant tunnelling across double barrier structures". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285640.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Wilkinson, Paul Bryan. "Quantum chaos in resonant tunnelling diodes". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363557.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Turner, Thomas Stephen. "Optical studies of resonant tunnelling structures". Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284112.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Manson-Smith, Sacha Kinsey. "Investigation into scanning tunnelling luminescence microscopy". Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366826.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Dudeney, William Leonard. "Novel displacement sensing : towards robotic tunnelling". Thesis, Loughborough University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392510.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Cockburn, John William. "Electron tunnelling microscopy at free surfaces". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304447.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Apachitei, Geanina. "Tunnelling effects in multiferroic tunnel junctions". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/94010/.

Testo completo

Abstract (sommario):

The demands from electronic devices have always been to be portable, fast, non-volatile, more intelligent and to consume low energy. One way towards this goal is to introduce multifunctionality of materials in devices. Ferromagnetism and ferroelectricity are two order parameters that can be coupled in a limited number of multiferroics and their coexistence implies the control over magnetisation and polarisation with both electric and magnetic fields. Similar properties were observed at ferromagnetic/ferroelectric thin film interfaces and attracted attention, since high quality thin film devices can be easily obtained nowadays through monitoring in real time of their structural and physical properties. This effect was observed also in tunnel junction configurations, devices which are formed from metallic electrodes separated by a very thin insulating barrier. By combining a barrier with various ferroelectric order parameters (ferroelectric, antiferroelectric, ferrielectric) and ferromagnetic electrodes, multi-field controlled multi-state non-volatile memory devices can be obtained. Tunnelling processes, especially in junctions containing d orbital elements are not completely understood and need deeper investigation. In this thesis, multiferroic tunnel junctions with La0:7Sr0:3MnO3/PbTiO3/Co structure are shown to be functional down to 3 unit cells. Moreover, the domain structure is shown to change with thickness, going through complex patterns including toroidal flux closure structures. The fabrication and working principle of the novel antiferroelectric tunnel junctions are reported for the first time using La0:7Sr0:3MnO3/PbZrO3/Co structures. Both investigated systems exhibit a multiferroic interface characterised by a magnetoelectric coupling which can be tailored by switching the ferroelectric polarisation.

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Roller, Eric Tobias. "Nanofabrication with the scanning tunnelling microscope". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624355.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Chorniy, Vladimir Zinovievich. "Novel applications of scanning tunnelling microscopy". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624931.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Bryant, B. E. M. "Scanning tunnelling microscopy of bilayer manganites". Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19980/.

Testo completo

Abstract (sommario):

This thesis describes experimental work carried out on bilayer manganites with the general composition R_{2-2x}A_{1+2x}Mn_2O_7, where R is a trivalent rare earth cation and A is a divalent alkaline-earth cation. Experiments have been carried out primarily using Scanning Tunnelling Microscopy (STM) and Spectroscopy (STS); bulk electrical transport, MPMS and LEED measurements have also been made. The primary results are obtained from single crystal samples of PrSr_2Mn_2O_7. This compound provides a surface suitable for STM study when cleaved at low temperature in ultra-high vacuum: atomic resolution can be readily achieved. The expected square lattice is observed, together with a larger scale surface modulation which is not presently explained. In some areas of the PrSr_2Mn_2O_7 surface a population of adatoms and surface vacancies is observed. STS data indicate that adatoms carry a negative charge compared to the rest of the surface, and vacancies a positive charge: the adatoms and vacancies are interpreted as oxygen adatoms and oxygen vacancies. A detailed study is made of the oxygen adatoms and vacancies: this is believed to be the firrst such study made on a manganite surface. Oxygen adatoms on the PrSr_2Mn_2O_7 surface are found to be mobile: hopping and adatom-vacancy recombination are observed. Additional results are reported on the layered manganite compound La_{2-2x}Sr_{1+2x}Mn_2O_7 at a range of cation doping x. For the LaSr_2Mn_2O_7 compound (x = 0.5) spectroscopic variation has been identi_ed in a variable-temperature STS survey. This indicates the coexistence of two surface electronic phases, possibly the charge ordered and antiferromagnetic phases.

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Johannissen, Linus. "Computational studies of enzymic hydrogen tunnelling". Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/29979.

Testo completo

Abstract (sommario):

The importance of proton tunnelling in the reaction catalysed by the heterotetrameric enzyme aromatic amine dehydrogenase (AADH) has been extensively studied both kinetically and computationally, and the availability of crystal structures for key reaction intermediates makes this an ideal system for studying the involvement of dynamics in catalysis. Multi-nanosecond molecular dynamics simulations revealed that the motions of the reacting groups are not correlated with motions within the enzyme, and that the overall motions of the donor and acceptor atoms are not focused towards each other. Nevertheless, certain key motions are required to achieve tunnelling, and these were identified from spectral density analysis as corresponding to a 165 cm-1 promoting vibration. This vibration is not part of a large network of vibrations, but is instead inherent within the substrate, as confirmed by high-level frequency calculations of the isolated substrate. Comparing hybrid simulations of the heterotetramer and an isolated monomer of AADH revealed that this vibration is crucial for reducing the tunnelling distance and the height of the barrier separating the reactant from product by moving the system up the potential energy surface. numerical modelling of the experimental rates revealed that the promoting vibration is compatible with the reaction kinetics and compatible with the tunnelling distance derived from a concomitant computational analysis, and that the presence or absence of such a vibration may not be easily identified experimentally. This represents the first example of a short-range oscillation acting as a promoting vibration, and opens the door to new experimental methods for studying enzymic tunnelling and potentially for exploiting enzymes in biocatalysis by selectively exciting specific vibrational modes.

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Razvan, Baba. "Resonant tunnelling diodes for THz communications". Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/30870/.

Testo completo

Abstract (sommario):

Resonant tunnelling diodes realised in the InGaAs/AlAs compound semiconductor system lattice-matched to InP substrates represent one of the fastest electronic solid-state devices, with demonstrated oscillation capability in excess of 2 THz. Current state-of-the-art offers a poor DC-to-RF conversion efficiency. This thesis discusses the structural issues limiting the device performance and offers structural design optimums based on quantum transport modelling. These structures are viewed in the context of epitaxial growth limitations and their extrinsic oscillator performance. An advanced non-destructive characterisation scheme based on low-temperature photoluminescence spectroscopy and high-resolution TEM is proposed to verify the epitaxial perfection of the proposed structure, followed by recommendations to improve the statistical process control, and eventually yield of these very high-current density mesoscopic devices. This work concludes with an outward look towards other compound semiconductor systems, advanced layer structures, and antenna designs.

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Figueiredo, José Maria Longras. "Optoelectronic properties of resonant tunnelling diodes". Doctoral thesis, Universidade do Porto. Reitoria, 2000. http://hdl.handle.net/10216/14347.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Zhou, Bo. "Tunnelling-induced ground displacements in sand". Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28394/.

Testo completo

Abstract (sommario):

The main objective of this research was to examine the effects that relative density and stratification have on greenfield soil displacements above tunnels in sandy ground. Data from a series of plane-strain centrifuge tests on tunnels in silica sand are presented. The relative density of the sand samples ranged from 90% to 50% in the tests. The soil displacement data were examined to determine features of greenfield settlement, both surface and subsurface. The effects that relative density and stratification have on the settlement trough shape is demonstrated and discussed. Some interesting features of tunnelling in sandy ground are revealed in the analysis.

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Schutz, Reinhard. "Numerical modelling of shotcrete for tunnelling". Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5674.

Testo completo

Abstract (sommario):

Shotcrete is a special type of concrete which was invented at the beginning of the 20th century and is nowadays an important support element for tunnels constructed with the New Austrian Tunnelling Method (NATM). Immediately after tunnel excavation shotcrete is sprayed onto the tunnel walls at high pressure in order to provide temporary support. Unfortunately, in the past very little attention has been given to the development of sophisticated material laws for shotcrete, since its design and application was mainly based on experience. However, current design practice, such as that applied in the design of the new Crossrail tunnels, requires sophisticated modelling of shotcrete behaviour in numerical analysis of tunnel-soil interaction. Such models are not readily found in the literature, as they have been developed mainly for structural, rather than geotechnical applications. In this thesis, a constitutive model for the time-dependent behaviour of shotcrete has been developed within the framework of elasto-plasticity. Two independent yield surfaces control the behaviour of shotcrete in multiaxial loading conditions for both compression and tension. The model formulation is based on strain hardening/softening plasticity, where the expansion and contraction of the yield surfaces are governed by normalised plastic strains. Cracking of the shotcrete is considered within the smeared crack concept. Furthermore, the proposed material law includes the time-dependency of stiffness and strength behaviour. The reducing deformability of the shotcrete during cement hydration has been taken into account. The model has been extended to account for creep, shrinkage and hydration temperature induced deformations at early shotcrete ages. After a robust implementation into the Imperial College Finite Element Program (ICFEP), model calibration and validation have been performed for shotcrete experiments taken from the literature. The developed constitutive model has then been applied to the analysis of a typical tunnel construction in London Clay, modelling the early age material properties of the shotcrete tunnel lining in detail for various excavation schemes. Finally, it has been shown that the proposed constitutive model is capable of reproducing the complex behaviour of young shotcrete at early ages and can be applied successfully to boundary value problems in geotechnical engineering.

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Thorpe, Jason Peter. "Ground movements during tunnelling in sand". Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/957.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Figueiredo, José Maria Longras. "Optoelectronic properties of resonant tunnelling diodes". Tese, Universidade do Porto. Reitoria, 2000. http://hdl.handle.net/10216/14347.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Weiss, Christian [Verfasser]. "STM beyond vacuum tunnelling : scanning tunnelling hydrogen microscopy as a route to ultra-high resolution / Christian Weiss". Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1028003706/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Hughes, Keith Howard. "A time domain description of large amplitude mode vibrations in small molecules". Thesis, Bangor University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391757.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Anderson, I. "A study of the dynamic cutting characteristics of roadheader cutting heads". Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315535.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Othaman, Zulkafli Bin. "Hydrostatic pressure studies of semiconductor heterostructures and Schottky diodes". Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295450.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Nussbaumer, Thomas Niklaus Nussbaumer Thomas Nikolaus. "Superconducting tunnelling junctions as X-ray detectors /". [S.l.] : [s.n.], 1998. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12596.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Bayani, Babak [Verfasser]. "Interacting quantum-dissipative tunnelling systems / Babak Bayani". Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1019453125/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Savage, Kevin John. "Plasmonic interactions in the quantum tunnelling regime". Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/244105.

Testo completo

Abstract (sommario):

Driven by exciting new research and applications, top-down and bottom-up fabrication techniques are producing ever more intricate, reproducible, plasmonic nano-architectures with gaps and junctions approaching the single nanometre and atomic scales. Such atomic-sized features promote the intersection of physics, chemistry and biology in plasmonics. Consequently, understanding light-matter interactions in such closely spaced, electromagnetically coupled, metallic nanosystems is of vital importance to a tremendous variety of current and future nanophotonic technologies. This thesis describes the first dynamically controlled, optically broadband, experimental investigations of light-driven plasmonic coupling between two metal nanostructures with sub-nanometre separation. A new experimental apparatus and nanosystem alignment technique was developed to enable the required sub-nanometre inter-nanoparticle geometry to be created and probed. Two conducting atomic force microscopy tips with nanoparticle functionalised apices are brought into nanoscale `tip-to-tip' axial alignment with dynamically-controlled spacing and ultra-wide optical access. Resonant electrical parametric mixing, created by oscillating the electromechanically coupled tips, is utilised to extract an electronic signal due to nanoscale changes in inter-tip position. Experimental results match theory confirming the viability of the technique. By functionalising the tip apices, this unique multi-functional observation platform allows the plasmonic response of nanoparticle dimers with sub-nanometre separations to be characterised. By simultaneously capturing both the electrical and optical properties of tip-mounted gold nanoparticles with controllable sub-nanometre separation, the first evidence for the quantum regime of optically driven tunnelling plasmonics is revealed in unprecedented detail. It is demonstrated that quantum mechanical effects are critically important at approximately the 0.3 nm scale where spatially non-local tunnelling plasmonics controls the optical response. All observed phenomena are in good agreement with a recently developed quantum-corrected model of plasmonic systems. The findings imply that tunnelling establishes a quantum limit for plasmonic field enhancement and confinement. Additionally, the work suggests the highly enhanced local density of photonic states in nanoscale cavities could enable coherent plasmon-exciton coupling. This thesis prompts new experimental and theoretical investigations into quantum-domain plasmonic systems, and impacts the future of nanoplasmonic device engineering, nanoscale photochemistry and plasmon-mediated electron tunnelling.

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Pals, Pieter. "Tunnelling through quantum dots with Coulomb interaction". Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7578.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Barr, Matthew Valet. "Instrumented horizontal drilling for tunnelling site investigation". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37628.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Vorster, Theodore Eduard Beyerhaus. "The effects of tunnelling on buried pipes". Thesis, University of Cambridge, 2006. https://www.repository.cam.ac.uk/handle/1810/251988.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Avgerinos, Vasileios. "Numerical investigation of tunnelling beneath existing tunnels". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/39789.

Testo completo

Abstract (sommario):

Tunnels under large metropolitan cities have been constructed for almost two centuries. As the cities expand their surface and subsurface space become congested. The construction of the new Crossrail tunnels under central London, which has been on-going during the preparation of this thesis, has more than 30 interfaces with existing London underground tunnels. In this thesis the effects of excavating the Crossrail tunnels under the existing Central line tunnels below Bayswater road are explored and various aspects of tunnelling in London clay are investigated using the finite element code ICFEP (Imperial College Finite Element Program). The first part of this thesis focuses on the short and long-term behaviour of grey cast iron tunnel linings by modelling the cross-section of the Central line tunnels under Bayswater Road. The effect of the lining permeability on the lining response in terms of deformation and internal forces is highlighted. Simulations of a large-scale experimental set-up (that studies the lining behaviour) are made and ways to overcome some of the experimental limitations are presented. In the second part of the thesis the use of a sophisticated two surface kinematic hardening model for modelling tunnelling in stiff London clay is explored by analysing the Jubilee Line Extension under St. James's Park and the Crossrail tunnels under Hyde Park. The calibration of the model parameters against laboratory tests on intact samples and the modelling of previous stress history improve the predicted soil displacements due to tunnelling. In the last part of this thesis, a three-dimensional numerical model is used in order to qualitatively estimate the response of the Central line tunnels due to the excavation of the new Crossrail tunnels. Despite the simplifications made, the numerical predictions show that finite element analysis is a useful and reliable tool to analyse such complicated problems.

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Visser, Jason Willem. "Temperature control instrumentation for scanning tunnelling microscopy". Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1232.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Wong, Terence Kin Shun. "Fabrication and characterization of ultrasmall tunnelling devices". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241122.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

48

Sleigh, Anne Katherine. "Inelastic electron tunnelling spectroscopy of adsorbed molecules". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.346406.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Rigopoulos, Nickolas. "Scanning tunnelling microscopy of thin film polysi". Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488360.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Bylin, Johan. "Analysis of a spin-particle tunnelling junction". Thesis, Uppsala universitet, Materialteori, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-254984.

Testo completo

Abstract (sommario):

This project is to analyse the energy spectrum of a spin-molecular tunnelling junction which is composed of molecules confined between two conducting metallic leads. By letting a continuous stream of electrons flow across the junction the molecules can interact with each other with an indirect force called exchange interaction, and those exchange interactions which are of interest in this project are described by models called the Heisenberg, the Ising and the Dzyaloshinski-Moriya models. The molecules may also interact with themselves anisotropically and if there is an external magnetic field there will be yet another kind of interaction. The goal of this project is to see the contribution of all these spin interactions and how they affect the resulting energy spectrum under the variation of the junction's chemical potential and the voltage bias between the leads. This project is of a theoretical nature where the models are analytically adapted for a restricted scenario and is later on numerically calculated to be graphed and analysed. The models are restricted to only consider molecules of same spin and approximated to only consider interactions between closest neighbouring molecules. The results are composed of both analytically derived energy values and numerical computed values which show that there exists certain critical values of the variation parameters which naturally splits the ground state of the system and that the self-interaction may further split the degenerate ground state. A possible outcome of these result could be the possibility to control the magnetic order of the molecules to either be locked in an anti-ferromagnetic configuration or be easily mixed by manipulating the chemical potential or the voltage bias.
Detta projekt handlar om att analysera energispektrumet från en spinn-molekyl-tunnelkor-sning som består av molekyler instängda mellan två ledande metaller. När en kontinuerlig elektronström korsar tunnelkorsningen så kan molekylerna växelverka med varandra via en indirekt kraft kallad utbytesinteraktion, och de utbytesinteraktioner som är relevanta i denna uppställning beskrivs av de så kallade Heisenberg-, Ising- och Dzyaloshinski-Moriya-modellerna. Molekylerna kan också växelverka med sig själva anisotropt och om det finns ett externt magnetfält så tillkommer ytterligare en interaktionsterm. Målet för detta projekt är att se hur alla dessa spinnbidrag påverkar det slutliga energispektrumet under variation av korsningens kemiska potential och spänningen mellan metalledarna. Projektet är teoretiskt lagt på så sätt att modellerna är analytiskt anpassade för ett begränsat scenario samt att de är numeriskt beräknade så att energispektrumet kan plottas i grafer och analyseras. Modellerna är begränsade för molekyler av samma spinn och är approximerade så att endast närmsta-granne-interaktioner är beaktade. Resultaten är uppdelade i både analytiskt framtagna energivärden samt numeriskt beräknande energinivåer och båda visar att det finns kritiska värden på variationsparametrarna som automatiskt delar grundtillståndet för systemet samt att självinteraktionerna ytterligare kan dela det degenererade grundtillståndet. Ett möjligt utfall av dessa resultat är att de kan användas till att kontrollera systemets magnetiska ordning på så sätt att det antingen är låst i en antiferromagnetisk konfiguration eller med enkelhet kan mixas genom att ändra den kemiska potentialen eller spänningen mellan metalledarna.

Gli stili APA, Harvard, Vancouver, ISO e altri

Offriamo sconti su tutti i piani premium per gli autori le cui opere sono incluse in raccolte letterarie tematiche. Contattaci per ottenere un codice promozionale unico!