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Enlighten (146.418 recursos)

Enlighten is the University of Glasgow's institutional repository service for published research material including peer-reviewed journal articles, published conference papers,books and book chapters

Subject = Q Science: QC Physics

Mostrando recursos 1 - 20 de 188

  1. Nano- and micro-fabrication techniques for improving thermoelectric materials and generators

    Paul, Douglas J.
    Nanostructured materials can be used to improve the performance of thermoelectric materials. The theories required to understand how nanostructures affect the electric conductivities, thermal conductivities and Seebeck coefficients will be reviewed before examples will be provided of the enhanced performance that can be achieved through low-dimensional structures. Some of the best thermoelectric material performance results from the literature will be presented and compared to the best bulk material results. A review will also be presented of microfabricated thermoelectric generators with explanations of the key output parameters and how these parameters can be optimised for applications. Microfabricated thermoelectric generators require less...

  2. Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling

    Pascoe, D.J.; Russell, A.J.B.; Anfinogentov, S.A.; Simões, P.J.A.; Goddard, C.R.; Nakariakov, V.M.; Fletcher, L.
    Aims. We extend recently developed seismological methods to analyse oscillating loops which feature a large initial shift in the equilibrium position and investigate additional observational signatures related to the loop environment and oscillation driver. Methods. We model the motion of coronal loops as a kink oscillation damped by mode coupling, accounting for any change in loop length and the possible presence of parallel harmonics in addition to the fundamental mode. We apply our model to a loop which rapidly contracts due to a post-flare implosion (SOL2012-03-09) and a loop with a large lateral displacement (SOL2012-10-20). Results. The seismological method is used to...

  3. Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling

    Pascoe, D.J.; Russell, A.J.B.; Anfinogentov, S.A.; Simões, P.J.A.; Goddard, C.R.; Nakariakov, V.M.; Fletcher, L.
    Aims. We extend recently developed seismological methods to analyse oscillating loops which feature a large initial shift in the equilibrium position and investigate additional observational signatures related to the loop environment and oscillation driver. Methods. We model the motion of coronal loops as a kink oscillation damped by mode coupling, accounting for any change in loop length and the possible presence of parallel harmonics in addition to the fundamental mode. We apply our model to a loop which rapidly contracts due to a post-flare implosion (SOL2012-03-09) and a loop with a large lateral displacement (SOL2012-10-20). Results. The seismological method is used to...

  4. Can substorm particle acceleration be applied to solar flares?

    Birn, Joachim; Battaglia, Marina; Fletcher, Lyndsay; Hesse, Michael; Neukirch, Thomas
    Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular we investigate the effects of the collapsing field ("collapsing magnetic trap") below a reconnection site, which has been demonstrated to be the major acceleration mechanism causing energetic particle acceleration and injections observed in Earth's magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high shear, field (low beta) with low and moderate shear, finite-pressure...

  5. Can substorm particle acceleration be applied to solar flares?

    Birn, Joachim; Battaglia, Marina; Fletcher, Lyndsay; Hesse, Michael; Neukirch, Thomas
    Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular we investigate the effects of the collapsing field ("collapsing magnetic trap") below a reconnection site, which has been demonstrated to be the major acceleration mechanism causing energetic particle acceleration and injections observed in Earth's magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high shear, field (low beta) with low and moderate shear, finite-pressure...

  6. A miniaturized 4K platform for superconducting infrared photon counting detectors

    Gemmell, Nathan R.; Hills, Matthew; Bradshaw, Tom; Rawlings, Tom; Green, Ben; Heath, Robert M.; Tsimvrakidis, Konstantinos; Dobrovolskiy, Sergiy; Zwiller, Val; Dorenbos, Sander; Crook, Martin; Hadfield, Robert H.
    We report on a miniaturized platform for superconducting infrared photon counting detectors. We have implemented a fibre-coupled superconducting nanowire single photon detector in a Stirling/Joule–Thomson platform with a base temperature of 4.2 K. We have verified a cooling power of 4 mW at 4.7 K. We report 20% system detection efficiency at 1310 nm wavelength at a dark count rate of 1 kHz. We have carried out compelling application demonstrations in single photon depth metrology and singlet oxygen luminescence detection.

  7. Stability of equidimensional pseudo–single-domain magnetite over billion-year timescales

    Nagy, Lesleis; Williams, Wyn; Muxworthy, Adrian R.; Fabian, Karl; Almeida, Trevor P.; Conbhuí, Pádraig Ó; Shcherbakov, Valera P.
    Interpretations of paleomagnetic observations assume that naturally occurring magnetic particles can retain their primary magnetic recording over billions of years. The ability to retain a magnetic recording is inferred from laboratory measurements, where heating causes demagnetization on the order of seconds. The theoretical basis for this inference comes from previous models that assume only the existence of small, uniformly magnetized particles, whereas the carriers of paleomagnetic signals in rocks are usually larger, nonuniformly magnetized particles, for which there is no empirically complete, thermally activated model. This study has developed a thermally activated numerical micromagnetic model that can quantitatively determine the...

  8. Stability of equidimensional pseudo–single-domain magnetite over billion-year timescales

    Nagy, Lesleis; Williams, Wyn; Muxworthy, Adrian R.; Fabian, Karl; Almeida, Trevor P.; Conbhuí, Pádraig Ó; Shcherbakov, Valera P.
    Interpretations of paleomagnetic observations assume that naturally occurring magnetic particles can retain their primary magnetic recording over billions of years. The ability to retain a magnetic recording is inferred from laboratory measurements, where heating causes demagnetization on the order of seconds. The theoretical basis for this inference comes from previous models that assume only the existence of small, uniformly magnetized particles, whereas the carriers of paleomagnetic signals in rocks are usually larger, nonuniformly magnetized particles, for which there is no empirically complete, thermally activated model. This study has developed a thermally activated numerical micromagnetic model that can quantitatively determine the...

  9. Stability of equidimensional pseudo–single-domain magnetite over billion-year timescales

    Nagy, Lesleis; Williams, Wyn; Muxworthy, Adrian R.; Fabian, Karl; Almeida, Trevor P.; Conbhuí, Pádraig Ó; Shcherbakov, Valera P.
    Interpretations of paleomagnetic observations assume that naturally occurring magnetic particles can retain their primary magnetic recording over billions of years. The ability to retain a magnetic recording is inferred from laboratory measurements, where heating causes demagnetization on the order of seconds. The theoretical basis for this inference comes from previous models that assume only the existence of small, uniformly magnetized particles, whereas the carriers of paleomagnetic signals in rocks are usually larger, nonuniformly magnetized particles, for which there is no empirically complete, thermally activated model. This study has developed a thermally activated numerical micromagnetic model that can quantitatively determine the...

  10. Stability of equidimensional pseudo–single-domain magnetite over billion-year timescales

    Nagy, Lesleis; Williams, Wyn; Muxworthy, Adrian R.; Fabian, Karl; Almeida, Trevor P.; Conbhuí, Pádraig Ó; Shcherbakov, Valera P.
    Interpretations of paleomagnetic observations assume that naturally occurring magnetic particles can retain their primary magnetic recording over billions of years. The ability to retain a magnetic recording is inferred from laboratory measurements, where heating causes demagnetization on the order of seconds. The theoretical basis for this inference comes from previous models that assume only the existence of small, uniformly magnetized particles, whereas the carriers of paleomagnetic signals in rocks are usually larger, nonuniformly magnetized particles, for which there is no empirically complete, thermally activated model. This study has developed a thermally activated numerical micromagnetic model that can quantitatively determine the...

  11. Probing dynamical gravity with the polarization of continuous gravitational waves

    Isi, Maximiliano; Pitkin, Matthew; Weinstein, Alan J.
    The direct detection of gravitational waves provides the opportunity to measure fundamental aspects of gravity which have never been directly probed before, including the polarization of gravitational waves. In the context of searches for continuous waves from known pulsars, we present novel methods to detect signals of any polarization content, measure the modes present and place upper limits on the amplitude of nontensorial components. This will allow us to obtain new model-independent, dynamical constraints on deviations from general relativity. We test this framework on multiple potential sources using simulated data from three advanced-era detectors at design sensitivity. We find that...

  12. Indraft Supersonic Wind Tunnel for Shock Train Investigations

    Gnani, F.; Zare-Behtash, H.; Kontis, K.

  13. Indraft Supersonic Wind Tunnel for Shock Train Investigations

    Gnani, F.; Zare-Behtash, H.; Kontis, K.

  14. Indraft Supersonic Wind Tunnel for Shock Train Investigations

    Gnani, F.; Zare-Behtash, H.; Kontis, K.

  15. Experimental Investigations of Three-Dimensional Shock-Vortex Loop Interaction: Shock Reflection and Diffraction Phenomena

    Ukai, T.; Zare-Behtash, H.; Kontis, K.; Obayashi, S
    Estimation of the sonic boom and its effect are necessary to develop supersonic transport vehicles. The typical sonic boom is produced by the shock waves generated from a supersonic transport vehicle cruising at more than the speed of sound. The shock waves pass through the real atmosphere and reach ground level. The sonic boom pressure signatures are affected by atmospheric conditions such as turbulence, humidity, and temperature [1]. These atmospheric conditions cannot be controlled; however, they must be considered. Atmospheric effects have to be well understood because it is extremely important to accurately estimate the sonic boom magnitude at ground...

  16. Experimental Investigations of Three-Dimensional Shock-Vortex Loop Interaction: Shock Reflection and Diffraction Phenomena

    Ukai, T.; Zare-Behtash, H.; Kontis, K.; Obayashi, S
    Estimation of the sonic boom and its effect are necessary to develop supersonic transport vehicles. The typical sonic boom is produced by the shock waves generated from a supersonic transport vehicle cruising at more than the speed of sound. The shock waves pass through the real atmosphere and reach ground level. The sonic boom pressure signatures are affected by atmospheric conditions such as turbulence, humidity, and temperature [1]. These atmospheric conditions cannot be controlled; however, they must be considered. Atmospheric effects have to be well understood because it is extremely important to accurately estimate the sonic boom magnitude at ground...

  17. Experimental Investigations of Three-Dimensional Shock-Vortex Loop Interaction: Shock Reflection and Diffraction Phenomena

    Ukai, T.; Zare-Behtash, H.; Kontis, K.; Obayashi, S
    Estimation of the sonic boom and its effect are necessary to develop supersonic transport vehicles. The typical sonic boom is produced by the shock waves generated from a supersonic transport vehicle cruising at more than the speed of sound. The shock waves pass through the real atmosphere and reach ground level. The sonic boom pressure signatures are affected by atmospheric conditions such as turbulence, humidity, and temperature [1]. These atmospheric conditions cannot be controlled; however, they must be considered. Atmospheric effects have to be well understood because it is extremely important to accurately estimate the sonic boom magnitude at ground...

  18. The role of surface roughness on the electron confinement in semiconductor quantum dots

    Macêdo, Rair; Sena, Michael S.; Costa e Silva, Jusciane; Chaves, Andrey; da Costa, José A. P.
    Using the effective mass approximation, we present a theoretical study of surface roughness effects on electron energies in semiconductor quantum dots, which are demonstrated to increase up to approximately 6%.

  19. Beam Shifts of Far-Infrared Radiation on Reflection off the Anisotropic Crystal LiYF4

    Macêdo, Rair; Dumelow, Thomas; da Costa, José A.P.
    We investigate the Goos-Hänchen shifts associated with phonons in the anisotropic crystal LiYF4. In p-polarization the shifts can be either positive or negative, and various mechanism are discussed.

  20. Tunable All-Angle Negative Refraction in Antiferromagnets

    Macêdo, Rair; Dumelow, Thomas; da Costa, José A.P.
    We consider how the magnon response of an antiferromagnet may be used to induce negative refraction at terahertz frequencies and how the angle of refraction may be tuned using an external magnetic field.

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