Дисертації з теми "Currents fluctuations"
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1
Ceballos, Lina Isabel. "North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26552.
Анотація:
Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009.Committee Chair: Di Lorenzo, Emanuele; Committee Member: Bracco, Annalisa; Committee Member: Webster, Peter J.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
2
Motz, Thomas [Verfasser]. "Heat transport in open quantum chains: currents, fluctuations, and rectification / Thomas Motz." Ulm : Universität Ulm, 2019. http://d-nb.info/1184429863/34.
3
Ballu, Xavier. "Measurement of equilibrium supercurrent noise in superconductor-normal ring and current-phase relation of helical hinge states of tungsten ditelluride." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP189.
Анотація:
Une jonction SNS formée par un matériau non-supraconducteur (N) entre deux contacts supraconducteurs (S) peut être traversée par un supercourant porté par des états liés d'Andreev (ABS) qui est déterminé par la différence de phase supraconductrice aux bornes des contacts supraconducteurs. La valeur de ce courant et sa dynamique sont des sondes très sensibles des propriétés de transport cohérent et topologique dans le matériau non-supraconducteur.Une première expérience dans laquelle un fil mésoscopique (Au) est inséré dans un anneau supraconducteur a permis d'explorer la dynamique des ABS. A température finie, les fluctuations thermiques des ABS doivent donner lieu à des fluctuations du supercourant et donc à une dissipation à fréquence finie dont l'amplitude dépend de leur temps de relaxation comme prédit par le théorème fluctuation-dissipation. En couplant cet anneau à un résonateur supraconducteur nous avons réussi à mesurer indépendamment les fluctuations du supercourant à l'équilibre et la dissipation qui apparait quand on soumet l'anneau à un flux magnétique oscillant. Cette expérience constitue la première confirmation de ce théorème dans une jonction SNS.Dans une seconde partie, nous avons mis en évidence le caractère topologique du ditellure de tungstène (WTe2) à travers la mesure de la relation supercourant/phase en utilisant un dispositif d'interférence quantique supraconducteur (SQUID) asymétrique, constitué de deux jonctions SNS en parallèle. La forme en dent de scie de la relation courant-phase pour une facette latérale du cristal et la survie du supercourant à fort champ magnétique révèlent le caractère balistique et unidimensionnel du transport le long de certaines arêtes sur plus de 500 nm. Ceci est une signature de la présence d'états unidimensionnels protégés du désordre dans ce matériaux confirmant les prédictions d'une phase proche d'un isolant topologique d'ordre supérieur pour ce matériauAn SNS junction formed by a non-superconducting material (N) between two superconducting contacts (S) can sustain a supercurrent carried by Andreev bound states (ABS) which is determined by the superconducting phase difference across the superconducting contacts. The value of this current and its dynamics are very sensitive probes of the coherent and topological transport properties in the non-superconducting material.An initial experiment in which a mesoscopic wire (Au) is inserted into a superconducting ring has made it possible to explore the dynamics of the ABS. At finite temperature, thermal fluctuations in ABS should give rise to fluctuations in the supercurrent and therefore to a finite-frequency dissipation, the amplitude of which depends on their relaxation time, as predicted by the fluctuation-dissipation theorem. By coupling this ring to a superconducting resonator, we were able to measure independently the fluctuations in the supercurrent at equilibrium and the dissipation that occurs when the ring is subjected to an oscillating magnetic flux. This experiment constitutes the first confirmation of this theorem in an SNS junction.In the second part, we demonstrated the topological character of tungsten ditelluride (WTe2) by measuring the supercurrent/phase relation using an asymmetric superconducting quantum interference device (SQUID), consisting of two SNS junctions in parallel. The sawtooth shape of the current-phase relation for a lateral facet of the crystal and the robustness of the supercurrent at high magnetic field reveals the ballistic and one-dimensional character of the transport along certain edges over more than 500 nm. This is a signature of the presence of one-dimensional states protected from disorder in this material, confirming the predictions of a phase close to a higher-order topological insulator for this material
4
Škvarenina, Ľubomír. "Charakterizácia tenkovrstvových solárnych článkov a analýza mikroštruktúrnych defektov." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-447549.
Анотація:
Thin-film solar cells based on an absorber layer of chalcogenide compounds (CIGS, CdTe) are today among the most promising photovoltaic technologies due to their long-term ability to gain a foothold in mass commercial production as an alternative to conventional Si solar cells. Despite this success, the physical origin of the defects present in the thin films are still insufficiently elucidated, especially in the compounds of the chalcopyrite family Cu(In_{1x},Ga_{x})(S_{y},Se_{1y})_{2}. The research focuses on the identification and analysis of microstructural defects responsible for the electrical instability of chalcopyrite-based thin-film solar cells with a typical heterostructure arrangement ZnO:Al/i-ZnO/CdS/Cu(In,Ga)Se_{2}/Mo. The non-uniform polycrystalline nature of semiconductor materials in this complex multilayer structure requires a comprehensive analysis of electro-optical, structural and compositional properties associated with the actual morphology at the macroscopic, microscopic or even nanoscopic level. The observed predominant ohmic or non-ohmic current conduction in the dark transport characteristics was also reflected in the slope deviations of the excessive noise fluctuations, which were in the spectral domain exclusively in the form of flicker noise with dependency S_{i} ~ f^{1}. Spatially resolved electroluminescence based on stimulated photon emission by charge carriers injecting into the depletion region, not only showed a significantly inhomogeneous distribution of intensity in planar heterojunction under forward bias, but also revealed light emitting local spots in reverse bias due to a trap-assisted radiative recombination through the high density of defect states. Microscopic examination of the defect-related light emitting spots revealed rather extensive defective complexes with many interruptions through the layers, especially at the heterojunction CdS/Cu(In,Ga)Se_{2} interface. Besides, the high leakage current via these defective complexes subsequently led to a considerable local overheating, which caused a clearly observable structural and morphological changes, such as deviations in absorber layer stoichiometry due to Cu–In–Ga–Se segregation, Cu-rich and Ga-rich grains formation with an occurrence of Se-poor or Cu_{x}Se_{y} secondary phases regions, material redeposition accompanied by evaporation of ZnO:Al/i-ZnO/CdS layers together with the formation of Se structures on the surface around the defects. Within the research, analytical modelling of transport characteristics was implemented with parameters extraction of individual transport mechanisms to understand the non-ohmic shunt behaviour due to leakage current. In addition to the proper current path along the main heterojunction, the proposed model contains parasitic current pathways as a consequence of recombination-dominated charge transport or current conduction facilitated by multi-step tunnelling via high density of mid-gap defect states in the depletion region, ohmic leakage current caused by pinholes or low-resistance paths along grain boundaries in Cu(In,Ga)Se_{2}, or space-charge limited current due to metals diffusion from the ZnO:Al layer and grid Ag contacts through disruptions in i-ZnO/CdS layers.
5
Mayer, Peter (Peter Matthew) 1978. "Current fluctuations in semiconductor devices." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87247.
6
Zorkot, Mira. "Current fluctuations in ionic nanopores." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:0a8def87-04ee-4f5f-8619-92000d70b7f2.
Анотація:
From electrical current to ecological and biological systems, fluctuations are characterised based on the frequency dependence of the power spectral density. Surprisingly - given the diversity of the systems considered - the power spectra of many systems reveal an inverse power- law dependence on the frequency f in certain regimes. This ubiquitous phenomenon famously known as '1/f noise' has triggered an abundance of investigations aimed at understanding its mechanism. Recently, '1/f noise' has also been observed in the ionic electric current through biological ion channels, nanometre-scale membrane pores and solid-state nanopores. Identifying and understanding the source of 1/f noise in nanopores emerges as a crucial prerequisite to design nanopore systems for their use in technological devices, such as nanopore- based DNA sequencers. At the same time, the current power spectrum in nanopores contains a wealth of information which, if extracted, would help towards a detailed characterisation of the nanopore's microscopic properties. To analyse the mechanism behind the occurrence of 1/f in nanopores, we study nanopores using Langevin-dynamics simulations and analytical methods. Ions move through the pore driven by an applied electric field, and the induced current is recorded. The power spectral density calculated from this data indicates the existence of a power law frequency dependence in an extended frequency regime. To verify a series of conclusions drawn from experimental investigations, we systematically vary all parameters characterising the system, including the geometry, the electric field, the ion density and the flexibility of the pore wall. Furthermore, we derive an analytical expression for the current power spectral density and compare it to the results from the Langevin-dynamics simulations. Finally, we evaluate the role of hydrodynamic interactions and find that it does not induce any major changes in the current power spectral density. Our studies allow us to uncover the mechanism that leads to the power law behaviour: interactions among the ionic components.
7
Wiener, Alexander David. "Non-equilibrium current fluctuations in graphene." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47737.
Анотація:
We analyze experimental evidence of transport through evanescent waves in graphene, reconciling existing experimental data with theory. We propose novel experimental geometries that provide even more compelling evidence of evanescent waves. We investigate the shot noise generated by evanescent modes in graphene for several experimental setups. For two impurity-free graphene strips kept at the Dirac point by gate potentials, separated by a long highly doped region, we find that the Fano factor takes the universal value F=1/4. For a large superlattice consisting of many strips gated to the Dirac point, interspersed among doped regions, we find F=1/(8ln2). These results differ from the value F=1/3 predicted for a disordered metal, providing an unambiguous experimental signature of evanescent mode transport in graphene. For a graphene nano-ribbon transistor geometry, we explain that the experimentally observed anomalous voltage scale of the shot noise can arise from doping by the contacts to the electrical circuit. These observations provide strong evidence of evanescent mode transport in graphene.
8
Lee, Hyunwoo. "Electric current fluctuations in mesoscopic systems." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38380.
9
Meidell, Andreas. "International contracts and currency fluctuations /." Oslo : Cappelen Akademisk Forl, 2007. http://www.gbv.de/dms/zbw/55551854X.pdf.
10
Becker, Thijs, Katherine Nelissen, and Bart Cleuren. "Current fluctuations in boundary driven diffusive systems." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198029.
11
Becker, Thijs, Katherine Nelissen, and Bart Cleuren. "Current fluctuations in boundary driven diffusive systems." Diffusion fundamentals 24 (2015) 5, S. 1-2, 2015. https://ul.qucosa.de/id/qucosa%3A14519.
12
Roehling, Allison. "Exchange Rate Fluctuations, Currency Invoicing, and International Trade." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19295.
Анотація:
Economic intuition suggests that real currency depreciation should lead to long run improvement in a country's trade balance. The short run implications of real depreciation are relatively unknown. The current literature suggests that the short run relationship between trade and real exchange rates is country-specific. This literature has not explored if product and trading partner characteristics play a role in this relationship. This dissertation explores how heterogeneity in trade influences the responsiveness of trade to real exchange rate fluctuations. To my knowledge, this is the first set of papers exploring this heterogeneity.
The first paper of this dissertation explores heterogeneity with U.S. commodity-level trade data. Trade responsiveness to real fluctuations varies across product and trading partner characteristics. I find no evidence of long run gains in trade following real depreciation, suggesting that currency manipulation policies meant to improve a country’s trade balance may have no effect on trade in the long run.
Prices in international trade contracts with U.S. firms are largely invoiced in U.S. dollars. However, the current literature suggests that the currency in which these prices are set should affect the relationship between trade and real exchange rates in the short run. The second paper of this dissertation explores the implications of currency invoicing patterns using Japanese commodity-level trade data. I find that the response of trade to real fluctuations may differ in the short and long run across product and trading partner characteristics. I also find that the response of trade in the long run may be correlated with comparative advantage.
The third paper of this dissertation explores the implications of foreign exchange market liberalization in Japan following the Asian Financial Crisis. I find that liberalization, coupled with financial market reforms, resulted in trade being less responsive to real fluctuations. I also find no evidence of long run trade balance improvement before or after liberalization and that the reform may have eliminated temporary short run gains, suggesting that currency manipulation policies may have no effect on short or long run trade.
13
Pietzonka, Patrick [Verfasser], and Udo [Akademischer Betreuer] Seifert. "Thermodynamic bounds on current fluctuations / Patrick Pietzonka ; Betreuer: Udo Seifert." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/116360402X/34.
14
Gokce, Aisha. "Low frequency current and resistance fluctuations in magnetic tunnel junctions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 203 p, 2009. http://proquest.umi.com/pqdweb?did=1896928791&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
15
Chandial, Amarajit Singh. "High frequency fluctuations, timescales and heterokedasticity in currency rates." Thesis, Royal Holloway, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394840.
16
Feng, Zi Min 1982. "Current fluctuations driven by a sudden turn-off of external bias." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101845.
Анотація:
The purpose of this thesis is to report a theoretical investigation on the current-current correlation and noise in the tmnsient quantum transport regime. In particular, we calculate current correlations when the bias voltage of a LDL quantum device is suddenly turned off. Namely, we consider the situation that when time t < 0 the device is in a steady-state under bias Vb, when t > 0 the bias is turned off to zero. Under such a bias, the transport current l goes from a finite steady-state value 10 at t < 0 to zero at large times. When electronic structure of the leads as well as well as the device scattering region are to be taken into account, it is a difficult problem to calculate the time dependent current-current correlation. However, for the sharp step-down bias shape, we discover that the time-dependent problem can be solved exactly for non-interacting systems.
17
Chou, Kuang-Yi. "Sodium channel regulatory mechanisms : current fluctuation analysis on frog skin epithelium." Doctoral thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/27148.
Анотація:
This project examined the role of the cytoskeleton in regulatory mechanisms of the amiloride-sensitive Na⁺ channels in isolated frog skin epithelium. The epithelium from ventral frog skin is a model tissue which has proved significant in our understanding of the basic principles involved in water and Na⁺ homeostasis. In particular, this project examines ways in which local (non-hormonal) and hormonal regulatory mechanisms adjust the Na⁺ permeability of apical membranes of frog skin epithelium. Both mechanisms contain factors that are known to increase the apical membrane Na⁺ permeability mainly by increases in the number of open channels. The origin of these new open channels is unknown but, it is postulated that they could arise either by activation of quiescent channels already present in the apical membrane, or by recruitment of channels from cytoplasmic stores. Regarding the latter hypothesis, we also examined the idea that the cytoskeleton might somehow be involved in the insertion of Na⁺ channels within vesicles, into the apical membrane. This is based on the fact that the cytoskeleton is involved in a similar mechanism whereby, in the toad urinary bladder, anti-diuretic hormone (ADH) causes the insertion of aggregates with water channels. Much current interest focuses on the role of the cytoskeleton in the regulation of epithelial Na⁺ channels. To test this hypothesis, we used noise analysis to examine the effects of disrupting the cytoskeleton, on two different mechanisms which bring about changes in open channel densities. The mechanisms are: (1) lowering mucosal Na⁺ concentration (non-hormonal), and (2) addition of arginine-vasopressin (A VP) (hormonal). Non-hormonal, autoregulatory changes in apical membrane Na⁺ conductance were examined by investigating the effects of reducing the mucosal Na⁺ concentration. Our results showed that lowering the mucosal Na⁺ concentration induced large increases in the open channel density in order to stabilise the transport rate. In addition, we observed an average 55-60% increase in the open channel probability, which implies that in epithelium from Rana fuscigula, changes of channel open probability are also an important mechanism in the autoregulation of channel densities in response to a reduction in mucosal Na⁺. The hormonal control of Na⁺ channels by A VP has been intensively studied by noise analysis and the patch clamp. Our results confirmed previous reports that A VP increases the Na⁺ transport rate by increasing the number of open Na⁺ channels, primarily through large changes in the total number of channels, without a significant change in open probability. Regarding the role of the cytoskeleton in regulation of Na⁺ channels and/or its possible role in control of inserting putative vesicles with Na⁺ channels, we studied the effects of disrupting the cytoskeleton on the two regulatory mechanisms. Disrupting microtubules with colchicine had no, or very little effect on either of the regulatory mechanisms. On the other hand, the integrity of the microfilaments was very important for the autoregulatory changes in the number of open channels. After cytochalasin B treatment, lowering the mucosal Na⁺ concentration did not result in the usual compensatory changes in channel densities. There was no prior evidence that cytochalasin B had any actual effect on the F-actin network in the frog skin epithelium. Accordingly, modified cytochemical techniques were designed to demonstrate and localise F-actin in the epithelial granular cells. The direct immunofluorescent method proved useful, but did not allow sufficient resolution to examine the changes to different populations of actin in the cells. We then modified an immunogold method to suit our conditions, and the results demonstrated the localisation of different pools of F-actin and showed the effects of the cytochalasin B and vasopressin.
18
Limbourn, Andrew John. "The condition at settlement of the western rock lobster, Panulirus cygnus George : spatial and temporal fluctuations." University of Western Australia. School of Animal Biology, 2010. http://theses.library.uwa.edu.au/adt-WU2010.0062.
Анотація:
The condition at settlement of the western rock lobster pueruli presumably reflects both their energetic condition in reaching the near shore and subsequent recruitment into adult populations. In recruiting to the near shore the pueruli swim across the continental shelf where oceanographic conditions are complex and likely influence the success of recruitment. The results from the biochemical studies are interpreted in light of the oceanography off the coast of Western Australia. I investigated the nutritional condition of larval phyllosomata, post-larval puerulus and first instar post-pueruli juveniles of the spiny lobster, Panulirus cygnus, to determine energy use during the non-feeding transitional puerulus stage. Biochemical analyses of lipid, fatty acid (FA) and protein revealed that lipid, in particular phospholipids, is primarily used for energy during the nonfeeding puerulus stage. Monounsaturated FA showed the greatest decline with development, whereas the polyunsaturated FA showed a high degree of sparing, suggesting these FA are not used as a substrate for energy production. The knowledge gained on the biochemistry of energy use in P. cygnus was then used to investigate the spatial and temporal variability in the nutritional condition, in particular lipid condition, of puerulus collected at three near shore locations (Alkimos, Jurien Bay and Dongara) along the Western Australia coast, and one offshore location (Houtman Abrolhos Islands). The one offshore location was chosen as I hypothesised that arriving pueruli are likely to be in a better state of nutrition than those arriving at more coastal locations where the potential journey from offshore larval feeding grounds to the near shore is considerably greater. This element of my research showed lipid levels to be inversely related, generally, to shelf width but were variable, suggesting pueruli may travel complex trajectories to reach nearshore settlement. The lipid and FA composition of pueruli was also consistent with spatial and seasonal variation in Leeuwin Current and coastal productivity regimes.
19
Wright, P. S. "The accurate analysis of smoothly fluctuating harmonics applied to the calibration of harmonic analysers." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843265/.
Анотація:
The aim of this research is to develop an accurate method for the analysis of signals composed of fluctuating harmonics. The results obtained of analysis are applied to the calibration of harmonic analysis instruments. A new method is presented suitable for the accurate analysis of smoothly fluctuating harmonic signals. The method is based on a model of signals with a known period, in which the harmonics are individually modulated by polynomial functions normalised over a sampled signal sequence time. Using this model, a decomposition method is developed such that the modulating polynomials can be recovered from a signal. The polynomial decomposition method leads to a piece-wise analysis of the waveform. Two methods based on least squares and splines respectively, are developed with the aim of giving continuity to the piece-wise analysis. Comparisons of the new method with the short time Fourier transform are given. Having defined a test signal and obtained and accurate analysis of it properties, it can be used to calibrate harmonic analysers. For a given applied signal, analysis with these devices can give rise to variation in results as a function of the phase between the signal and the STFT windows. This result distribution due to variable phase (RDVP) is discussed and examples are given for various signals. The RDVP complicates the calibration process due to the spread of results that occur when testing the device. A method is developed to find the RDVP for an applied signal that uses the polynomial decomposition method to find the modulation functions of each harmonic in the applied calibration signal. Having found the RDVP for an applied signal, it is necessary to fit the results of the analyser under test, to the distribution. The random nature of the phase makes the systematic comparison of the theoretical and measured distributions difficult to achieve. A novel method that uses multiple phase shifted modulated harmonics is presented. By comparing the results of the analyser under test to the distributions of each of the phase-shifted harmonics, a best-fit phase shift can be determined and the required calibration comparison made. Key words: time-frequency analysis, demodulation, harmonic analysis, fluctuating harmonics, waveform metrology, calibration of harmonic analysers.
20
Ellsworth, Charles S. "Foreign currency fluctuation allowances in Department of Defense acquisition appropriations." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA276410.
Анотація:
Thesis (M.S. in Financial Management) Naval Postgraduate School, December 1993.Thesis advisor(s): Richard D. Milligan ; O. Moses. "December 1993." Includes bibliographical references. Also available online.
21
Micchi, Gianluca. "Mechanical signatures of the current-blockade instability in suspended carbon nanotubes." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0337/document.
Анотація:
Le couplage fort entre le transport électronique dans une boîte quantique à un seul niveau et un oscillateur nano-mécanique couplé capacitivement peut conduire à une transition vers un état mécaniquement bistable et bloqué en courant. Son observation est à portée de main dans les expériences de pointe menées sur les nanotubes de carbone. Nous étudions donc la réponse mécanique du système et plus précisément la fonction spectrale de déplacement, la réponse linéaire à une solicitation externe et le comportement pendant le retour à l'équilibre. Nous montrons qu'il existe une relation étroite entre les grandeurs électriques (telles le courant électrique et la fonction spectrale des fluctuations du courant) et mécaniques. Nous constatons qu'en augmentant le couplage électromécanique, les deux fonctions spectrales présentent un pic qui s'élargit et se déplace vers les basses fréquences alors que le temps de déphasage de l'oscillateur se raccourcit. Ces effets sont maximaux à la transition où les non-linéarités dominent la dynamique et sont robustes vis-à-vis de l'effet des fluctuations extérieures et de la dissipation. Ces caractéristiques fortes ouvrent la voie à la détection de la transition vers l'état de blocage du courant dans des dispositifs actuellement étudiées par plusieurs groupesThe strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nano-mechanical oscillator may lead to a transition towards a mechanically-bistable and blocked-current state. Its observation is at reach in carbonnanotube state-of-art experiments. Therefore, we investigate the mechanical response of the system, namely the displacement spectral function, the linear response to a driving, and the ring-down behavior, and the electric response, namely the electric current and current spectral function. We show that a close relation between electric and mechanical quantities exists. We find that, by increasing the lectromechanical coupling, the peak in both spectral functions broadens and shifts at low frequencies while the oscillator dephasing time shortens. These effects are maximum at the transition where nonlinearities dominate the dynamics, and are robust towards the effect of external uctuations and dissipation. These strong signatures open the way to detect the blockade transition in devices currently studied by several groups
22
Sivré, Émile. "Electrical fluctuations and heat flow in a quantum composite circuit." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS548.
Анотація:
L'interaction de Coulomb influence fortement toutes les propriétés de transport des circuits composites quantique à basse température. Dans cette thèse, nous étudions les fluctuations de courant et le flux de chaleur dans un circuit quantique, composé de plusieurs canaux de conduction élémentaires. Nous utilisons la mesure combinée des corrélations croisées et des auto-corrélations des fluctuations de courant, ce qui nous permet d'extraire séparément, d'une part, le bruit de grenaille provenant du partitionnement des électrons via un canal partiellement transmis et, d'autre part, la température des électrons dans le dispositif. Nous commençons notre investigation dans le cas où un canal quantique élémentaire arbitraire est inséré dans un circuit linéaire. Dans ce cas, nous établissons expérimentalement une relation reliant la suppression de conductance induite par l'interaction de Coulomb et la variation du bruit de grenaille en fonction de la tension. Deuxièmement, dans le même circuit, nous mesurons le bruit de grenaille au travers d'un canal élémentaire unique résultant du transfert de charges induit par un pur gradient thermique. Troisièmement, nous étudions l'effet de l'interaction de Coulomb sur le flux de chaleur électronique. Dans un circuit composé exclusivement de canaux balistiques, nous démontrons expérimentalement le blocage de Coulomb de la chaleur systématique de l'un des canaux. Au-delà de la limite balistique, nous observons un nouveau mécanisme sur le flux de chaleur relié à la fois au partitionnement électronique à travers un canal non balistique et à l'interaction de CoulombThe Coulomb interaction strongly influences all transport properties of quantum composite circuits at low temperature. In this thesis, we investigate the current fluctuations and the flow of heat in a quantum circuit, composed of several elementary conduction channels. We use combined measurement of cross-correlations and auto-correlations of the current fluctuations, allowing us to extract separately, on the one hand, the current shot noise coming from the partitions of electrons through a partially transmitted channel and, on the other hand, the temperature of the electrons in the device. We start our investigation with an arbitrary elementary quantum channel embedded in a linear circuit. In this case, we establish experimentally a relation connecting the conductance suppression induced by the Coulomb interaction and the shot noise variation as a function of the voltage. Second, in the same circuit, we measure the shot noise through a single elementary channel resulting from the transfer of charge induced by a pure thermal bias. Third, we investigate the effect of Coulomb interaction on the electronic heat flow. In a circuit exclusively composed of ballistic channels, we demonstrate experimentally the systematic heat Coulomb blockade of one of the channels. Beyond the ballistic limit, we observe a new heat flow mechanism connected to both the electron-partition through a non-ballistic channel and to the Coulomb interaction
23
Adom, Assandé Désiré. "Currency substitution, macroeconomic interdependence and real exchange rate fluctuations in selected African countries /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1402174551&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Анотація:
Thesis (Ph. D.)--Southern Illinois University Carbondale, 2007."Department of Economics." Keywords: Real exchange rate fluctuations, Currency substitution, Macroeconomic interdependence, Real exchange rate, African, Exchange rate fluctuations Includes bibliographical references (p. 120-128). Also available online.
24
Han, Tian. "Flow cell separation in fluctuating g-field." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11105.
Анотація:
Field flow fractionation of particles in rotating coiled column has been investigated in recent year. In contrast to the classical mode of field flow fractionation in narrow channels, the use of rotating coiled columns offers the possibility of large sample loading. In this thesis, the potential for new cell separation methods based on the use of flow fractionation in fluctuating g-fields generated in rotating coil columns is examined. The effects of operational conditions (flow rate and rotational speed – Chapter 3 and Chapter 5); cell properties (cell flexibility – Chapter 4); and column shapes (different inner diameters and coil geometries – Chapter 6) on the flow behaviour of a model system of red blood cells (RBCs) from different species, which differ markedly in size, shape & density, flowing in a single phase of buffered saline have been characterised. Operational Conditions: For a particular rotational speed, there was a minimum flow rate which caused all the cells to be retained in the column and a maximum flow rate at which all cells were eluted. Both the minimum and maximum flow rate were increased when a higher rotational speed was applied. Differences in the behaviour of sheep & hen RBCs have been used to develop a separation method using a continuously increasing flow gradient. This separation could be speeded up by using a step flow gradient. The effects of cell load and rotational direction on the behaviour of RBCs in the column was also studied in this thesis. Cell Properties: The minimum flow rate was found to correlate with cell diameter/cell volume of the RBCs as expected for a sedimentation related process and was partially described by a theoretic equation developed for particles by Fedotov and colleagues (Fedotov et al. 2005). However cell dependent departures from this equation were found which appear to indicate that cell specific surface properties may also be involved for cells (Chapter 3). By contrast the maximum flow rate showed no correlation with cell diameter/cell volume. An effect of cell deformability on the flow separation behaviour of the cells has been demonstrated. Chemical fixation of sheep RBCs with glutaraldehyde rendered the normally deformable RBCs rigid and non-deformable and resulted in the fixed sheep RBCs eluting significantly earlier than unfixed sheep RBCs. This difference was great enough that a mixture of deformable (unfixed) and non-deformable (fixed) sheep RBCs could be separated. Fixed cells tended to show cell aggregation, which could be reduced by the addition of surfactant. Column Geometry: An effect of column shapes on the flow separation behaviour of cells has been demonstrated showing that the optimisation of column design is an important feature of this mode of cell separation. For columns with the same cross sectional area, a “horizontal” rectangular column provided better separation than a circular column and a “vertical” rectangular column gave the least efficient separation. A possible explanation for this behaviour is suggested the thinner sedimentation layer and less secondary flow. Differences in the behaviour of various species of RBCs in the “horizontal” rectangular column have been used to study the efficiency of separation of a mixture of sheep and hen RBCs, and a mixture of rabbit and hen RBCs. This work shows similarities and differences with other reports on cell/particle separations in rotating coiled columns in single phases and also in aqueous two phases systems (ATPS) and these are discussed. Fedotov P.S., Kronrod V.A. & Kasatonova O.N. (2005). Simulation of the motion of solid particles in the carries liquid flow in a rotating coiled column. J. Anal. Chem., 60, 4, 310-316.
25
Khajeh, Alijani Azadeh. "Deterministic and stochastic dynamics of multi-variable neuron models : resonance, filtered fluctuations and sodium-current inactivation." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/36845/.
Анотація:
Neurons are the basic elements of the networks that constitute the computational units of the brain. They dynamically transform input information into sequences of electrical pulses. To conceive the complex function of the brain, it is crucial to understand this transformation and identify simple neuron models which accurately reproduce the known features of biological neurons. This thesis addresses three different features of neurons. We start by exploring the effect of subthreshold resonance on the response of a periodically forced neuron using a simple threshold model. The response is studied in terms of an implicit one-dimensional time map that corresponds to the Poincar´e map of the forced system. Qualitatively distinct responses are found, including mode locking and chaos. We analytically find the stability regions of mode-locking solutions, and identify the transition to chaos through period-adding bifurcations. We show that the response becomes chaotic when the forcing frequency is close to the resonant frequency. Then we will consider an experimentally verified model with realistic spikegenerating mechanism and study the effect of filtered synaptic fluctuations on the firing-rate response of the neuron. Using a population density method as well as an efficient numerical method, we find the steady-state firing rate in two limits of fast and slow synaptic inputs and present the linear response theory for the firing rate of the model in response to both time-dependent mean inputs and time-dependent noise intensity. Finally, a novel model is introduced that incorporates threshold variability of neurons. We determine the modulation of the input-output properties of the model due to oscillatory inputs and in the presence of filtered synaptic fluctuations.
26
Nakanishi, Kunihito. "A study on magnetic fluctuations over the ionospheric E-region driven by the lower atmospheric phenomena." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215320.
27
Zhou, Zhibin. "Modeling and power control of a marine current turbine system with energy storage devices." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0094/document.
Анотація:
Ces travaux de thèse concernent l’étude de l’ensemble de la chaîne de puissance d’un système hydrolien utilisant des systèmes de stockage d’énergie pour améliorer la qualité de la puissance produite et la capacité de gestion des échanges d’énergie. Dans un premier temps, les différentes technologies de stockage d’énergie et leurs applications pour lisser les fluctuations de la puissance produite par le système hydrolien sont étudiées et comparées. Ensuite, une stratégie de lissage des fluctuations de la puissance, dues à l’effet de houle (fluctuations de courte durée), est proposée : elle associe une stratégie MPPT avec filtrage (au niveau de la génératrice) à l’utilisation de supercondensateurs pour lisser la puissance injectée au réseau. Puis il est proposé d’utiliser des batteries à circulation d’électrolyte pour la gestion quotidienne de la puissance d’une hydrolienne dans le contexte d’un réseau électrique isolé. Un système hybride hydrolien/batteries/diesel est étudié pour deux configurations simples : le cas d’une alimentation avec une hydrolienne comme sources principales et le cas où les générateurs diesels sont considérés comme sources dominantes. Enfin, des stratégies de limitation de puissance basées sur le défluxage de la génératrice pour contrôler la puissance de l’hydrolienne dans le cas de vitesses de courants marins élevées sont proposées. Dans ce contexte, le contrôle à puissance constante et à puissance maximale en cours de défluxage sont comparés. L’influence des paramètres de la génératrice sur les caractéristiques de fonctionnement commun de la turbine et la génératrice est également étudiéeThis PhD thesis models the whole power chain of a marine current turbine (MCT) system and investigates the use of energy storage devices to improve power quality and energy management capability. First, various energy storage technologies concerning their applications to address the power fluctuation phenomena in tidal current generation system are reviewed and compared. Then, a two-stage power smoothing control strategy for compensating swell-induced short-time fluctuations is proposed. The proposed control strategy uses a modified MPPT with filter strategy on the generator-side and supercapacitors on the grid-side for injecting a smoothed power to the grid. Afterwards, a flow battery system for daily energy management of a hybrid MCT/battery/diesel system is proposed. The MCT dominant power supply case and an island power supply (with diesel generators as the main source) are investigated. Finally, power limitation controls with a robust flux-weakening strategy for a PMSG-based non-pitchable MCT system are proposed for over-rated marine current speed periods. In this context, the constant power control and maximum power control modes at the flux-weakening stage are compared; and the influence of the generator parameters on the joint operating characteristics of the turbine and generator are also discussed
28
Gabsi, Mohamed Khémis. "Contribution a l'etude de la commutation dans les machines a courant continu associees a des convertisseurs statiques de puissance." Paris 6, 1987. http://www.theses.fr/1987PA066170.
29
Xu, Peng Ph D. Massachusetts Institute of Technology. "Polarimetry measurements of current density profile and fluctuation changes during lower hybrid experiments on Alcator C-Mod." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84391.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, September 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 179-186).
As a possible method to achieve steady-state plasma operation in a tokamak fusion reactor, Lower Hybrid Current Drive (LHCD) has been extensively studied on Alcator C-Mod. The measurement of current density profiles (or poloidal magnetic field or safety factor) is essential to the understanding of the LH physics. A polarimeter measures the line-integral of the electron density times the magnetic field parallel to a chord through the plasma, and is capable of deriving the current density profile with multi-chord measurements. A three-chord poloidally viewing far-infrared (FIR) polarimeter has therefore been developed for C-Mod. FIR optics, FIR detectors, electronics and mechanical components were custom designed and fabricated. Various sources of vibrations and systematic errors have been carefully dealt with. A synthetic polarimeter signal has been derived from density profiles from Thomson scattering and magnetic field profiles from EFIT. The polarimeter results confirm that the magnetic field profiles from Kinetic EFIT (with Motional Stark Effect and plasma pressure constraints) is much more accurate than those from normal EFIT (no internal constraints, central safety factor qo~0.9 5) during the LHCD. The polarimeter data were used to constrain qO, and the result shows that the current density profile is flattened, and qo increases to ~2 with strong LHCD. Experiments during LHCD with a plasma density scan, a current scan, and LH power and phase scans have been carried out. The Polarimetry observations confirm the off-axis current drive, and strongly decreasing driven current when the density exceeds a limit of about 1.Ox 102 0/m3 . They also indicate that the driven current is closer to the plasma edge for Ip ~820 kA than for I, ~580 kA, and that lower LH phasing is preferred for higher current drive efficiency. The polarimeter is the first diagnostic to measure core magnetic fluctuations in Alcator C-Mod. These include broadband magnetic fluctuations during EDA H-modes that are suppressed with the application of LH power.
by Peng Xu.
Ph.D.
30
Reid, M. T. (McMahon Thomas Homer). "Fluctuating surface currents : a new algorithm for efficient prediction of Casimir interactions among arbitrary materials in arbitrary geometries." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68983.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 161-163).
For most of its 60 year history, the Casimir effect was an obscure theoretical backwater, but technological advances over the past decade have promoted this curious manifestation of quantum and thermal fluctuations to a position of central importance in modern experimental physics. Dramatic progress in the measurement of Casimir forces since 1997 has created a demand for theoretical tools that can predict Casimir interactions in realistic experimental geometries and in materials with realistic frequency-dependent electrical properties. This work presents a new paradigm for efficient numerical computation of Casimir interactions. Our new technique, which we term the fluctuating-surface-current (FSC) approach to computational Casimir physics, borrows ideas from the boundary-element method of computational electromagnetism to express Casimir energies, forces, and torques between bodies of arbitrary shapes and materials in terms of interactions among effective electric and magnetic surface currents flowing on the surfaces of the objects. We demonstrate that the master equations of the FSC approach arise as logical consequences of either of two seemingly disparate Casimir paradigms-the stress-tensor approach and the path-integral (or scattering) approach-and this work thus achieves an unexpected unification of these two otherwise quite distinct theoretical frameworks. But a theoretical technique is only as relevant as its practical implementations are useful, and for this reason we present three distinct numerical implementations of the FSC formulae, each of which poses a series of unique technical challenges. Finally, using our new theoretical paradigm and our practical implementations of it, we obtain new predictions of Casimir interactions in a number of experimentally relevant geometric and material configurations that would be difficult or impossible to treat with any other existing Casimir method.
by M. T. Homer Reid.
Ph.D.
31
Doganay, Yasar Ozge. "Sudden Stops And The Adjustment Of Real Exchange Rates To Current Account Deficits." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610002/index.pdf.
Анотація:
This study aims to analyze the causes and consequences of sudden stops in international capital flows with special reference to the recent Turkish experience. We aim to investigate also the vulnerability of the Turkish economy to a sudden stop and compute the required change in the real exchange rates for a current account adjustment in the face of a sudden stop. The assessment of the economic and structural indicators, which are assumed to be related with the resilience of the economy against sudden stops, such as openness and dollarization, refers that the risk of experiencing a sudden stop has increased in Turkey in the last two years, despite a decrease in its exposure to the destructive effects of such shocks thanks to the structural improvements in the economy. Our empirical results based on a small open economy model with tradables and non-tradables suggest that a sudden stop that requires the closing of the current account imbalance in Turkey would necessitate a real depreciation of around 36 percent as of May 2008 under the assumption that international reserves were not used in order to mitigate the level and the effects of the adjustment. Although the effects of such a real depreciation may be milder due to the decreased currency mismatches in the public and banking sector, there is still the risk of experiencing a financial crisis following a sudden stop because of the high liability dollarization in the real sector.
32
Morris, Claude. "Grid-connected transformerless single-phase photovoltaic inverters: an evaluation on DC current injection and PV array voltage fluctuation." Thesis, Morris, Claude (2009) Grid-connected transformerless single-phase photovoltaic inverters: an evaluation on DC current injection and PV array voltage fluctuation. Other thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/3245/.
Анотація:
A number of political, environmental and technical factors have resulted in the increase of implementation of renewable technology including grid connected photovoltaic inverters. As a result, new topologies for grid connected inverters providing higher efficiencies and lower manufacturing costs have been developed. In particular, designs utilising transformerless topologies have steadily increased. While there are clear associated advantages of implementing these new transformerless topologies, new potential issues such as DC current injection and capacitive leakage currents are introduced. Part A of this report presents a clearly defined test circuit setup and procedure for testing DC current injection for grid-connected single-phase photovoltaic inverters implementing both transformerless and high frequency transformer topologies. The results demonstrated that the test circuit setup and testing procedure is suitable for inclusion in a future amendment to AS4777.2. It is however proposed that before these amendments are recommended, further investigation is required to determine what power levels all inverters are required to be tested at and how many tests per inverter are required. Part B of this report defines and models a variety of transformerless inverter topologies, switching schemes and output filter configurations and clearly defines their operation. All of these various models have been simulated to determine which designs are suitable for applications in regards to reducing capacitive leakage currents in an effort to eliminate potential risks to users and to ensure electromagnetic compatability. Two commercially available and one anonymous Grid-connected Transformerless Single-phase Photovoltaic Inverter models utilising a selection of the simulated topologies and switching schemes were experimentally tested to verify simulated results.
33
Yaman, Yasemin. "Domestic Credit Expansion, Capital Flows And Current Account Imbalances: Empirircal Analyses Fof Brazil And Turkey." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614950/index.pdf.
Анотація:
This thesis analyzes the interactions between domestic credit expansion, capital inflows and current account imbalances in a framework of empirical models carried out for Brazil and Turkey. In this context, three vector autoregressive (VAR) models are specified covering the time period between January 2002 and March 2012 for Brazil and 2003 January and 2012 March for Turkey. Real effective exchange rate (REER) and relative yield spreads formed with country specific Embi + indexes are also included in the estimations of the models. The analyses of the models show that capital inflows in these countries trigger the domestic credit expansion which create an upward pressure on import demands and affect current account balances negatively. The results support the implementation of domestic credit tightening policies to reduce the current account imbalances in these countries.
34
Wang, Yue. "Sensitivité de la méthode dite de mélange des courants pour la détection du déplacement nano-mécanique." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0659/document.
Анотація:
La détection des déplacements nano-mécaniques par les techniques de transport électronique a atteint un haut niveau de sensibilité et de polyvalence. Afin de détecter l'amplitude d'oscillation d'un oscillateur nano-mécanique, une technique largement utilisée consiste à coupler ce mouvement de façon capacitive à un transistor à un seul électron ou, plus généralement, à un dispositif de transport, et à détecter la modulation haute fréquence du courant à travers le mélange non linéaire avec un signal électrique à une fréquence légèrement désaccordée. Cette méthode, connue sous le nom de technique de mélange des courants, est utilisée notamment pour la détection de nanotubes de carbone suspendus et s'est avérée particulièrement efficace, ce qui a permis d'obtenir des records de sensibilité dans la détection de masse et de force. Dans cette thèse nous étudions théoriquement les conditions qui limitent la sensibilité de cette méthode dans différents types de dispositifs de transport. La sensibilité est un compromis entre le bruit, le bruit de rétroaction et la fonction de réponse. Cette dernière est proportionnel au couplage électromécanique. Pour ces raisons dans la thèse, nous étudions la fonction de réponse, l'effet des fluctuations de courant et de déplacement (back-action) dans les dispositifs de détection suivants: (i) le transistor métallique à électron unique, (ii) le transistor à un seul niveau électronique et (iii) le point quantique cohérent. La sensibilité optimale est obtenue, comme d'habitude, lorsque la rétroaction du dispositif de détection est égale au bruit du signal intrinsèque, ce qui, dans notre cas, est le bruit en courant. Nous avons constaté que les valeurs optimales typiques du couplage sont obtenues dans la limite de couplage fort, où une forte renormalisation de la fréquence de résonance est observée et une bistabilité de l'oscillateur mécanique est présente [comme discuté dans G. Micchi, R. Avriller, F. Pistolesi, Phys. Rev. Lett. 115, 206802 (2015)]. Nous trouvons donc des limites supérieures à la sensibilité de la technique de détection de mélange des courants. Nous considérons également comment la technique du mélange des courants est modifiée dans la limite où le taux de transmission tunnel devient comparable à la fréquence de résonance de l'oscillateur mécaniqueDetection of nanomechanical displacement by electronic transport techniques has reached a high level of sensitivity and versatility. In order to detect the amplitude of oscillation of a nanomechanical oscillator, a widely used technique consists of coupling this motion capacitively to a single-electron transistor or, more generally, to a transport device, and to detect the high-frequency modulation of the current through the nonlinear mixing with an electric signal at a slightly detuned frequency. This method, known as mixing-current technique, is employed in particular for the detection of suspended carbon nanotubes and has proven to be particularly successful leading to record sensitivities of mass and force detection. In this thesis we study theoretically the limiting conditions on the sensitivity of this method in different kind of transport devices. The sensitivity is a compromise between the noise, the back-action noise, and the response function. The latter is proportional to the electromechanical coupling. For these reasons in the thesis we study the response function, the effect of current and displacement (back-action) fluctuations for the following detection devices: (i) the metallic single electron transistor, (ii) the single-electronic level single electron transistor, and (iii) the coherent transport quantum dot. The optimal sensitivity is obtained, as usual, when the back-action of the detection device equals the intrinsic signal noise that, in our case, is the current noise. We found that the typical optimal values of the coupling are obtained in the strong coupling limit, where a strong renormalization of the resonating frequency is observed and a bistability of the mechanical oscillator is present [as discussed in G. Micchi, R. Avriller, F. Pistolesi, Phys. Rev. Lett. 115, 206802 (2015)]. We thus find upper bounds to the sensitivity of the mixing-current detection technique. We also consider how the mixing-current technique is modified in the limit where the tunneling rate becomes comparable to the resonating frequency of the mechanical oscillator
35
Зайцев, Олександр Васильович, Александр Васильевич Зайцев, Oleksandr Vasylovych Zaitsev та Є. С. Степаненко. "Сучасний стан валютного ринку України". Thesis, Сумський державний університет, 2020. https://essuir.sumdu.edu.ua/handle/123456789/78989.
Анотація:
В тезах надано характеристику валютного ринку України за напрямками: міжбанківський ринок та ринок продажу готівки. Також, розглянуто вплив на курси валют та на споживчий попит в умовах Covid-19.В тезисах дана характеристика валютного рынка Украины по направлениям: межбанковский рынок и рынок продажи наличных. Также, рассмотрено влияние на курсы валют и на потребительский спрос в условиях Covid-19.
The theses "give" a description of the Ukrainian foreign exchange market in the following areas: interbank market and cash sale market. Also, the impact on exchange rates and on consumer demand in Covid-19 conditions is considered.
немає
36
Домашенко, Марина Дмитрівна, Марина Дмитриевна Домашенко, Maryna Dmytrivna Domashenko, and A. Korol. "Fluctuations in the exchange rate: the pros and cons of business and the world economy as a whole." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/65802.
Анотація:
The nаtionаl currency – а monetаry unit thаt is аvаilаble for use on
the territory of а pаrticulаr stаte. In modern conditions currency rаte is formed,
like аny mаrket price, under the influence of supply аnd demаnd. The exchаnge
rаte is essentiаl for internаtionаl monetаry, credit аnd finаnciаl operаtions. The effect
of exchаnge rаte fluctuаtions hаve а fаr-reаching impаct on the economy.This
аpplies to both the business pаrticipаnts аnd consumers.
37
Khnayfes, Marcos Amoyr. "Efeitos da textura e heterogeneidade de substratos artificiais em função da velocidade da correnteza e da escala temporal sobre as comunidades de macroalgas de ambientes lóticos /." Rio Claro : [s.n.], 2010. http://hdl.handle.net/11449/87884.
Анотація:
Orientador: Ciro César Zanini BrancoBanca: Orlando Necchi Junior
Banca: Carla Ferragut
Resumo: A heterogeneidade do habitat vem sendo considerada a maior discriminadora da diversidade das comunidades em sistemas lóticos. Esta pode ser caracterizada por variáveis específicas tais como velocidade da correnteza, temperatura, tipo de substrato, nutriente e luz. Diversos estudos se propõem a investigar a relação entre heterogeneidade de habitat e a distribuição das comunidades algais, através de estratégias metodológicas que envolvem o uso e aplicação de critérios de amostragem a partir das comunidades algais dispostas em substratos artificiais. Levando-se em conta que muitas investigações sugerem que o tipo de substrato pode ser a principal variável influenciando a distribuição espacial e temporal das comunidades lóticas e, que raríssimos estudos são aplicados às macroalgas de ambientes lóticos e que estas, juntamente com as briófitas, são as principais responsáveis pela produção primária nestes ecossistemas, o presente estudo foi proposto com os seguintes objetivos: 1) fazer uma análise de biomassa, composição florística e riqueza macroalgal diante de diferentes texturas de substratos artificiais, bem como de padrões de heterogeneidade criados a partir de combinações de fragmentos dos substratos artificiais testados, na tentativa de se aproximar dos fenômenos ocorridos em rochas naturais; 2) avaliação da textura e heterogeneidade do substrato sob duas condições de velocidade de correnteza em um riacho artificial; e 3) avaliação da textura e heterogeneidade do substrato ao longo da escala temporal de 109 dias em riachos naturais. Os resultados mostraram que a abundância global das comunidades de macroalgas foi bastante baixa e semelhante entre os tratamentos de textura e heterogeneidade nos dois experimentos, sugerindo que os níveis de rugosidade e de complexidade do substrato não apresentaram relevante influência sobre as coberturas percentuais... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The heterogeneity of habitat has been considered the most discriminating of the diversity of communities in lotic systems. This can be characterized by specific variables such as velocity, temperature, substrate type, nutrient and light. Several studies are proposed to investigate the relationship between habitat heterogeneity and distribution of algal communities through strategic methods that involve the use and application of criteria for sampling from algal communities on artificial substrates placed. Taking into account that many investigations suggest that the substrate may be the main variable influencing the spatial and temporal distribution of lotic communities and that very few studies are applied to the lotic macroalgae and that these, together with bryophytes, are mainly responsible for primary production in these ecosystems, this study was proposed with the following objectives: 1) make an analysis of biomass, floristic composition and richness on macroalgal of different types of artificial substrates as well as patterns of heterogeneity created from combinations of fragments of artificial substrates tested in an attempt to get closer to the phenomena occurring in rock natural, 2) evaluation of texture and heterogeneity of the substrate with two different water flow in an artificial stream, and 3) evaluation of texture and heterogeneity of the substrate over the fluctuation time of 109 days in natural streams. The results showed that the overall abundance of macroalgal communities was quite low and similar between the treatment of texture and variety in both experiments, suggesting that levels of roughness and complexity of the substrate showed no relevant influence on the coverage percentages of the communities investigated. The velocity, in turn, influenced both the abundance and wealth, these decreasing at higher intensity. Richness was lower, particularly at higher surface... (Complete abstract click electronic acces below)
Mestre
38
Ghasemi, Sima. "An Analysis of the Effects of Exchange Fluctuations on Employment, Output and Productivity in Canada." Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23643.
Анотація:
Since the adoption of the North American Free Trade Agreement (NAFTA), the Canadian dollar has come to be regarded as a petro-currency. Consequently, rising prices of oil and gas (as well as other natural resources) would increase capital inflows that would lead to a higher exchange rate and contribute to the decimation of the export-oriented Canadian manufacturing sector by making Canadian products less competitive internationally. Some have argued that the Canadian economy has started to show symptoms related to the Dutch Disease. One important symptom is the slow rate of productivity growth, which consequently leads to the theory that Canada’s productivity performance depends significantly on the foreign exchange value of the domestic currency. This dissertation attempts to address these issues and seeks to solve the question of whether the Canadian economy is suffering from the Dutch Disease, as well as whether or not movements of the Canadian dollar are responsible for the low Canadian productivity growth since the 1990s.
39
Asano, Yasuhiro, Yuki Sawa, Yukio Tanaka, and Alexander A. Golubov. "Odd-frequency pairs and Josephson current through a strong ferromagnet." American Physical Society, 2007. http://hdl.handle.net/2237/11285.
40
Khnayfes, Marcos Amoyr [UNESP]. "Efeitos da textura e heterogeneidade de substratos artificiais em função da velocidade da correnteza e da escala temporal sobre as comunidades de macroalgas de ambientes lóticos." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/87884.
Анотація:
Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0
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khnayfes_ma_me_rcla.pdf: 366930 bytes, checksum: c69a2b0e76bf67d5eb27107a48b4bb18 (MD5)A heterogeneidade do habitat vem sendo considerada a maior discriminadora da diversidade das comunidades em sistemas lóticos. Esta pode ser caracterizada por variáveis específicas tais como velocidade da correnteza, temperatura, tipo de substrato, nutriente e luz. Diversos estudos se propõem a investigar a relação entre heterogeneidade de habitat e a distribuição das comunidades algais, através de estratégias metodológicas que envolvem o uso e aplicação de critérios de amostragem a partir das comunidades algais dispostas em substratos artificiais. Levando-se em conta que muitas investigações sugerem que o tipo de substrato pode ser a principal variável influenciando a distribuição espacial e temporal das comunidades lóticas e, que raríssimos estudos são aplicados às macroalgas de ambientes lóticos e que estas, juntamente com as briófitas, são as principais responsáveis pela produção primária nestes ecossistemas, o presente estudo foi proposto com os seguintes objetivos: 1) fazer uma análise de biomassa, composição florística e riqueza macroalgal diante de diferentes texturas de substratos artificiais, bem como de padrões de heterogeneidade criados a partir de combinações de fragmentos dos substratos artificiais testados, na tentativa de se aproximar dos fenômenos ocorridos em rochas naturais; 2) avaliação da textura e heterogeneidade do substrato sob duas condições de velocidade de correnteza em um riacho artificial; e 3) avaliação da textura e heterogeneidade do substrato ao longo da escala temporal de 109 dias em riachos naturais. Os resultados mostraram que a abundância global das comunidades de macroalgas foi bastante baixa e semelhante entre os tratamentos de textura e heterogeneidade nos dois experimentos, sugerindo que os níveis de rugosidade e de complexidade do substrato não apresentaram relevante influência sobre as coberturas percentuais...
The heterogeneity of habitat has been considered the most discriminating of the diversity of communities in lotic systems. This can be characterized by specific variables such as velocity, temperature, substrate type, nutrient and light. Several studies are proposed to investigate the relationship between habitat heterogeneity and distribution of algal communities through strategic methods that involve the use and application of criteria for sampling from algal communities on artificial substrates placed. Taking into account that many investigations suggest that the substrate may be the main variable influencing the spatial and temporal distribution of lotic communities and that very few studies are applied to the lotic macroalgae and that these, together with bryophytes, are mainly responsible for primary production in these ecosystems, this study was proposed with the following objectives: 1) make an analysis of biomass, floristic composition and richness on macroalgal of different types of artificial substrates as well as patterns of heterogeneity created from combinations of fragments of artificial substrates tested in an attempt to get closer to the phenomena occurring in rock natural, 2) evaluation of texture and heterogeneity of the substrate with two different water flow in an artificial stream, and 3) evaluation of texture and heterogeneity of the substrate over the fluctuation time of 109 days in natural streams. The results showed that the overall abundance of macroalgal communities was quite low and similar between the treatment of texture and variety in both experiments, suggesting that levels of roughness and complexity of the substrate showed no relevant influence on the coverage percentages of the communities investigated. The velocity, in turn, influenced both the abundance and wealth, these decreasing at higher intensity. Richness was lower, particularly at higher surface... (Complete abstract click electronic acces below)
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Bekkers, J. M. "Studies of single ion channels : Nonstationary sodium current fluctuations in squid axon, and patch clamp analysis of acetylcholine-activated channels in cultured rat skeletal muscle." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372643.
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Zhang, Cheng. "Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons with resonant nanoantennas." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLO007/document.
Анотація:
Les plasmons polaritons de surface (SPPs) jouent un rôle central en nanophotonique, parce que ce sont des modes optiques qui peuvent être confinés dans l’espace à l’échelle de 10 nm et dans le temps à l’échelle de 10 fs. L’excitation électrique des plasmons polaritons de surface par effet tunnel inélastique peut être ultrarapide et localisée, ce qui permet de développer une nanosource pour la nanophotonique intégrée en profitant pleinement du potentiel des polaritons plasmon de surface. Pourtant, ce processus est très inefficace avec un rendement de conversion typique de 10-7~10-5 plasmon par électron.Dans ce manuscrit de thèse, nous présentons une étude théorique et expérimentale qui vise à augmenter l’émission de plasmons de surface par effet tunnel inélastique avec une nano-antenne résonante. Nous avons développé un modèle théorique pour décrire l’émission de lumière à partir d’une jonction à effet tunnel en utilisant le théorème de fluctuation-dissipation. Nous proposons deux stratégies pour augmenter le rendement de conversion électron-plasmon. Nous introduisons un mode d’antenne résonnante confiné à l’échelle du nanomètre afin de renforcer le couplage entre le courant et le champ. En outre, nous introduisons l’hybridation d’un mode plasmonique metal/isolant/metal confiné et d’un mode d’antenne. Nous prédisons théoriquement que 30% de l’énergie émise par un dipôle est sous forme de SPP pour une longueur d’onde de travail de 800nm et une épaisseur d’isolant de 1 nm.Nous avons développé les processus de fabrication pour réaliser les antennes à effet tunnel en utilisant la configuration Al/AlOx/Au. L’antenne fabriquée présente une fonctionnalité robuste concernant les propriétés électriques et optiques. Nous montrons l’antenne permet de contrôler le spectre d’émission SPP, la polarisation d’émission SPP et renforcer l’efficacité des émissions de SPP de plus de 3 ordres de grandeur. La puissance totale émise sous forme de SPP est de l’ordre de 10 pW, quatre ordres de grandeur de plus que la puissance typique émise par une pointe de microscope à effet tunnelSurface plasmon polaritons (SPPs) plays a central role in nanophotonics because they are optical modes that can be confined in space at the 10 nm scale and in time at the 10 fs scale. Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons has the potential to be fast and localized so that it offers the opportunity to develop a nanosource for on-chip nanophotonics taking advantage of the full potential of surface plasmons polaritons. However, inelastic tunneling is rather inefficient with a typical electron-to-plasmon conversion efficiency of 10-7~10-5. In this thesis manuscript, we present a study for enhancing surface plasmon emission by inelastic tunneling electrons with a resonant nanoantenna. It consists of theoretical and experimental investigations. First, we have developed a theoretical model to describe the light emission from a tunnel junction based on the fluctuation-dissipation theorem. Second, we have theoretically demonstrated two strategies to improve the antenna SPP efficiency thus aiming to enhance electron-to-plasmon conversion efficiency. We introduce a resonant antenna mode with a sub-nanometer gap in order to enhance the coupling between the inelastic current and the the mode. Furthermore, we introduce the hybridization in a nanopatch antenna between a gap mode and an antenna mode to launch SPPs: we theoretically predict that 30% of the power emitted by a dipole is converted into SPP (working wavelength at 800nm) with a 1nm gap thickness. Third, we have developed the fabrication procedures to realize antenna tunnel junctions based on the Al/AlOx/Au configuration. The fabricated antenna junction shows a robust functionality both regarding electrical and optical properties. The antenna junction is demonstrated to control the SPP emission spectrum, the SPP emission polarization and enhance the SPP emission efficiency by over 3 orders of magnitude. The total SPP power emitted is in the range of 10 pW, four orders of magnitude larger than the typical fW power emitted by a scanning tunneling tip junction
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Wandery, Oscar. "Bitcoin: A Seemingly Rampant Elevator, or is Someone Pushing its Buttons? : A Case Study on Bitcoin’s Fluctuations in Price and Concept." Thesis, Södertörns högskola, Institutionen för samhällsvetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-24421.
Анотація:
This study looks at the price mechanism of the digital quasi-currency bitcoin. Through statistical analysis of secondary data a probable significant results regarding correlation and regression between price and different independent variables have been established. The final analysis is pointing towards network effects being a part of the determinants for the crypto-currency’s price. Complimentary to the quantitative study explained above, an implementation of hermeneutic analysis based on secondary theoretical sources, journalistic opinion and a professional qualified judgment has aided the author and study in conceptual understanding. This interpretation has semantic character, and takes a Socratic kickoff regarding the nature of bitcoin as a financial instrument. The analysis runs back and forth throughout the course of the study and finally intertwines with qualitative results in the discussion. It is the author’s impression that a significant dimorphism surrounds bitcoin, calling for a conceptual differentiation leading to practical rethinking. The study takes the shape of a case-study conducted over four months. The author’s location during the process of writing was Stockholm Sweden, but the gathered data is of transnational character.Den här studien tittar på prismekanismen hos den digitala kvasi-valören bitcoin. Genom statistisk analys av sekundärdata har sannolikt signifikanta resultat angående korrelation och linjärregrission mellan pris och olika oberoende variabler ettablerats. Den slutgiltiga analysen pekar mot att nätverksvariabler är delaktiga i avgörandet av krypto-valutans pris. Komplimentärt till den kvantitativa studen förklarad ovanför så har en implementation av hermeneutisk analys basserad på sekundära källor, journalistiska åsikter och ett professionellt kvalifiserat uttalande hjälpt författaren samt studien i dess konceptuella förståelse. Denna tolkning har semantisk karaktär, och tar Sokratisk avstamp gällande bitcoins natur som ett finansielt instrument. Analysen går fram och tillbaka genom uppsatsens gång, för att slutligen sammanvävas med de kvantitativa resultaten i uppsatsens diskussion. Det är denna förfatares intryck att en signifikant dimorphism omsluter bitcoin och kallar för en konceptuel differensiering som leder till praktiskt nytänkande. Studen tar formen av en fallstudie som genomförts om loppet av fyra månader. Författarens plats genom skrivandeprocessen var Stockholm Sverige, men den samlade datan har transnationell karaktär.
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Le, Roch Alexandre. "Analyse de l’augmentation et de la fluctuation discrète du courant d’obscurité des imageurs CMOS dans les environnements radiatifs spatiaux et nucléaires." Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0018.
Анотація:
Inspirés des technologies microélectroniques CMOS (Complementary Metal Oxide Semiconductor), les capteurs d’images CMOS sont largement utilisés dans de nombreuses applications grand public et prédominent sur le marché commercial des caméras intégrées. Au cours de la dernière décennie, de nombreuses avancées technologiques ont permis au capteur d’image CMOS d’atteindre d’excellentes performances ainsi qu’une faible consommation d’énergie. Par conséquent, ces imageurs deviennent des candidats essentiels pour un nombre croissant d’applications spatiales et nucléaires. Cependant, le comportement de ces dispositifs microélectroniques dans les environnements radiatifs nucléaires et spatiaux est encore mal compris. Par conséquent, il est nécessaire d’étudier les différents mécanismes qui conduisent à la dégradation des performances des capteurs d’images CMOS et en particulier à l’augmentation du courant d’obscurité, un signal parasite qui augmente avec les doses de radiations.Parmi ces doses de radiations, la dose dite de déplacement, relative à l’altération de la structure cristalline du silicium, reste peu étudiée par rapport à la dose dite ionisante. Dans les dernières technologies de capteurs d’images CMOS utilisant des photodiodes pincées, la dose ionisante n’est plus le mécanisme de dégradation dominant dès lors que la dose de déplacement est mise en jeu. La dose de déplacement devient le mécanisme de dégradation principal qui conduit à l’augmentation du courant d’obscurité. Ce travail se concentre principalement sur le rôle des défauts cristallins, créés par la dose de déplacement induits par les radiations, dans l’augmentation du courant d’obscurité des capteurs d’images CMOS. Un intérêt particulier est accordé aux défauts métastables qui sont probablement la cause des fluctuations discrètes et aléatoires du courant d’obscurité appelé : signal des télégraphistes. Cette étude présente un double enjeu :Le premier vise à contribuer à l’amélioration des connaissances des principes physiques mis en jeu dans le silicium cristallin face aux radiations. Les interactions particule-matière,associées à l’architecture spécifique des capteurs d’images, visent à fournir des outils fiables pour l’analyse des défauts induits par les radiations dans le silicium. Ces observations et résultats peuvent être étendus à tous les dispositifs à base de silicium et plus généralement aux autres dispositifs à semi conducteurs.Le second vise à identifier les différents mécanismes conduisant à l’augmentation du courant d’obscurité des capteurs d’images CMOS lorsqu’ils fonctionnent dans des environnements radiatifs. L’étude vise à identifier et à améliorer la connaissance des comportements des sources de courant d’obscurité dans le but d’optimiser les capteurs d’images CMOS pour les futures applications spatiales et nucléairesInspired by the microelectronic Complementary Metal Oxide Semiconductor (CMOS) technologies, CMOS image sensors are widely used in many consumer-grade applications and are predominant in the commercial market for embedded cameras. Over the past decade,numerous technological advances allowed state-of-the-art CMOS image sensors to achieve excellent performances as well as low-power consumption. Therefore, CMOS image sensors are becoming essential candidates for a growing number of high-end applications such as space and nuclear applications. However, the behavior of these microelectronic devices inspace and nuclear radiative environments is still under understanding. Hence, studies still investigate the different mechanisms that lead to the degradation of CMOS image sensor performances including the radiation-induced dark current increase, a parasitic signal that increases with radiation doses. Among these radiation doses, the so-called displacement dose,relative to the alteration of the crystalline structure of the silicon, remains poorly studied compared to the so-called ionizing dose. In the latest CMOS image sensor technologies using pinned photodiodes, the ionizing dose is no longer the main degradation mechanism when the displacement dose is at stake. From then on, the displacement dose becomes the principal degradation mechanism that leads to the dark current increase. This work mainly focuses onthe role of the crystalline defects, created by radiation-induced displacement damage, in the CMOS image sensor dark current increase. Particular interest is given to metastable defects,which are probably the cause of discrete and random fluctuations of the dark current called : Dark Current Random Telegraph Signal (DC-RTS). This study presents a double objective :The first aims to contribute to improving knowledge of the physical principles involved in crystalline silicon when facing radiations. Particle-matter interactions, combined with the specific architecture of image sensors, aim to provide reliable tools to analyze the radiation induced defects in silicon. Observations and findings can be extended to all silicon-based devices and more generally to other semiconductor-based devices.The second seeks to identify the different mechanisms leading to CMOS image sensor dark current increase when operating in radiative environments. The study aims to identify and improve knowledge on the behavior of dark current sources aiming to optimize CMOS image sensors for future space and nuclear applications
45
Барвінок, В. Ю. "Валютна складова конкурентоспроможності експортної продукції". Master's thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/71511.
Анотація:
Дипломна робота присвячена сутності валюти у розвитку конкурентоспроможності експортної продукції. Основною стратегією є розробка ефективного валютного менеджменту в зовнішньоекономічній діяльності підприємства. Основною метою цього дослідження є надання рекомендацій щодо покращення конкурентоспроможність експортної продукції ТОВ “Горобина”.The diploma work focuses on the essence of the currency in the developing export products competitiveness. The main strategy is developing effective currency management in international trade operations of enterprise. The main aim of this research is to give recommendations to improve the export products competitiveness of the LLC “Gorobina”.
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Durnez, Clémentine. "Analyse des fluctuations discrètes du courant d’obscurité dans les imageurs à semi-conducteurs à base de silicium et Antimoniure d’Indium." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0030/document.
Анотація:
Le domaine de l’imagerie a toujours fait l’objet de curiosité, que ce soitpour enregistrer une scène, ou voir au-delà des limites de l’oeil humain grâce aux détecteursinfrarouges. Ces deux types d’imagerie sont réalisés avec différents matériaux. Dans le domainedu visible, c’est le silicium qui domine, car son absorbance spectrale correspond bien au spectrevisible et que ce matériau a été très étudié dans les dernières décennies. Dans le domainede l’infrarouge, plus particulièrement le MWIR (Middle Wave InfraRed), l’InSb est un boncandidat car il s’agit d’un matériau très stable. Cependant, certaines contraintes telles qu’unebande interdite étroite peuvent être limitantes et cela nécessite une température d’opérationcryogénique. Dans ces travaux, un signal parasite commun à ces deux matériaux est étudié : ils’agit du signal des télégraphistes (RTS : Random telegraph Signal) du courant d’obscurité. Cephénomène provient d’un courant de fuite de l’élément photosensible du pixel (photodiode).En effet, même dans le noir, certains pixels des imageurs vont avoir une réponse temporellequi va varier de façon discrète et aléatoire. Cela peut causer des problèmes de calibration, oude la mauvaise détection d’étoiles par exemple. Dans cette étude, deux axes principaux sontétudiés : la caractérisation du signal pour pouvoir mieux l’appréhender, et la localisation dessources à l’origine du RTS dans la photodiode afin d’essayer de l’atténuerImaging has always been an interesting field, all the more so as it is nowpossible to see further than human eyes in the infrared and ultraviolet spectra. For each fieldof application, materials are more or less adapted : in order to capture visible light, Siliconis a good candidate, because it has been widely studied, and is also used in our everydaylife. Concerning the infrared, more particularly the MWIR spectral band, InSb has provedto be stable and reliable, even if it need to operate at cryogenic temperatures because ofa narrow bandgap.. In this work, a parasitic signal called Random Telegraph Signal (RTS)which appears in both materials (and also others, such as HgCdTe or InGaAs) is analyzed.This signal comes from the pixel photodiiode and corresponds to a discrete dark currentfluctuation with time, like blinking signals. This can cause detector calibration troubles, orfalse star detection for example. This study aims at characterizing RTS and localize the exactorigin in the photodiode in order to be able to predict or mitigate the phenomenon
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Chen, Wei. "Three essays on, Hedging in China's oil futures market ; Gold, oil and stock market price volatility links in the USA ; and, Currency fluctuations in S.E. and Pacific Asia." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/397/.
Анотація:
This thesis empirically evaluates three key financial and macroeconomic issues: Essay 1 examines the effectiveness of China fuel oil futures in hedging a domestic spot fuel oil position as well as hedging a spot position in the Singapore fuel oil market. To the best of our knowledge, this is the first study of this kind. Dynamic Bi-variate GARCH and constant volatility models are estimated to derive the optimal hedging ratios and hedging effectiveness of China fuel oil futures. That effectiveness is assessed by several criteria, for both in- and out-of-sample periods. Essay 2 aims to investigate the relationship between the oil, gold and US stock markets. By employing a Tri-variate GARCH(1,1) model, this is the first study to explore how volatility is transmitted among those three markets. Additionally, this is the first study to compare Tri-variate GARCH and Bi-variate GARCH modelling strategies as vehicles for determining the volatility interrelations between these markets. Essay 3 explores the power of conventional macroeconomic factors to explain the currency fluctuations over recent years, including the 1997 crises, in six Asian countries. Two regimes Markov Switching TGARCH and constant volatility models are used to determine the causes of market pressures on exchange rates, and the probability of the timing of a currency attack. The Markov Switching models do not require an ex-ante definition of a threshold value to distinguish stable and volatile state like Logit models do, and they can capture the appreciating currency attacks as well as the depreciating ones. The Markov Switching models are also compared with Multinomial Logit models in their ability to detect crises.
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Robertsson, Göran. "International portfolio choice and trading behavior." Doctoral thesis, Handelshögskolan i Stockholm, Finansiell Ekonomi (FI), 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:hhs:diva-624.
Анотація:
This thesis consists of four essays on topics relating to the fields of international portfolio choice, trading behavior, and asset pricing. "Direct Foreign Ownership, Institutional Investors, and Firm Characteristics" analyzes portfolios of Swedish stocks held by foreign investors. The analysis reveals that foreigners tilt their portfolios to firms with certain attributes. It is also shown that the seemingly specific preferences of foreign investors are driven by the fact that they are large institutional investors, and are not linked to their national origin. "Foreigners' Trades in Risky Assets: An assessment of Investment Behavior and Performance" analyzes foreigners' trading activities. It is shown that foreigners trade more than domestic investors. Further, they trade as non-informed trend followers in that they buy stocks that have recently done well. Nonetheless, after the liberalization of Sweden's stock market, foreigners' purchases have led to a permanent price increase and to a reduction in the cost of equity capital. "Exchange Rate Exposure, Risk Premia, and Firm Characteristics" shows that about fifty percent of Swedish listed firms are affected by exchange rate fluctuations. The sign and magnitude of exchange rate exposure are characterized across industries as well as firm attributes. The empirical analysis suggests that exposure can be eliminated through diversification, and that exchange rate risk is not priced. "Conditioning Information in Tactical Asset Allocation" examines whether investors can exploit the predictability in time-varying expected returns on Swedish stocks and bonds. It is shown that dynamic allocation strategies, based on conditioning information, significantly outperform several benchmark portfolios. This superior performance is not only statistically significant, it is economically large.Diss. Stockholm : Handelshögsk.
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Negri, Carlotta. "Controlling electron transport : quantum pumping and single-electron tunneling oscillations." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14670/document.
Анотація:
Exploiter des effets dépendants du temps pour induire et contrôler des courants à travers des conducteurs mésoscopiques et nanoscopiques est un enjeu majeur dans le domaine du transport quantique. Dans cette thèse, nous considérons deux systèmes de taille nanométrique pour lesquels un courant est induit grâce au couplage entre champs extérieurs dépendants du temps et le transport d'électrons. Nous étudions d'abord un problème de pompage quantique au sein d'un système à trois sites en configuration d'anneau, en considérant la possibilité d'induire un courant continu par modulation temporelle des paramètres de contrôle. Nous nous intéressons en particulier à la transition entre régime adiabatique et antiadiabatique en présence d'un mécanisme de dissipation modélisé par un couplage entre le système et un bain extérieur.Nous montrons que le modèle dissipatif admet une solution analytique complète valable pour la composante DC du courant à fréquence arbitraire. Ceci nous permet de bien comprendre comment le courant induit dépend de la fréquence de pompage. Nous nous concentrons ensuite sur un autre système de contrôle du courant exploitant le phénomène des oscillations tunnel à un électron (SETOs). Contrairement au cas précédent, ici la circulation d'un courant continu à travers un circuit comportant une jonction tunnel produit, pour le régime approprié, un courant quasi-périodique d'électrons. On étudie le spectre de bruit à température nulle d'une jonction tunnel dans différents environnements résistifs dans le but de déterminer les limites du régime des SETOs et de quantifier leur degré de périodicité. Nous généralisons par la suite les résultats à température finie et discutons des effets des fluctuations quantiquesExploiting time-dependent effects to induce and control currents through mesoscopic and nano\-scopic conductors is a major challenge in the field of quantum transport. In this dissertation we consider two nanoscale systems in which a current can be induced through intriguing mechanisms of coupling between excitations by external fields and electron transport.We first study a quantum pumping problem, analyzing the possibility to induce a DC response to an AC parametric driving through a three-site system in a ring configuration. We are interested in particular in the crossover between adiabatic and antiadiabatic driving regimes and in the presence of dissipation, which is accounted for by coupling with an external bath. We show that for a clever choice of this coupling the dissipative model admits a full analytical solution for the steady state current valid at arbitrary frequency, which allows us to fully understand the pumping-frequency dependence of the induced current. We then focus on a different current-controlling scheme exploiting the phenomenon of single-electron tunneling oscillations (SETOs). In this case, opposite to what happens for pumping, an AC effect, an almost periodic current of single electrons, arises through a tunnel junction circuit as a consequence of a DC bias. We study the zero-temperature noise spectrum of a tunnel junction in different resistive environments with the aim to determine the boundaries of the SETOs regime and quantify their quality in terms of periodicity. We then discuss the finite-temperature generalization and the possibility to account for the effects of quantum fluctuations
50
Festin, Örjan. "On the Zero and Low Field Vortex Dynamics : An Experimental Study of Type-II Superconductors." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3907.
Анотація:
Dynamic properties of type-II superconductors have been experimentally studied in zero and low magnetic fields using SQUID magnetometry and I–V measurements.
In zero magnetic field close to the critical temperature, the physical properties of type-II superconductors are dominated by spontaneously created vortices. In three dimensions (3D) such vortices take the form of vortex loops and in two dimensions (2D) as vortex-antivortex pairs.
The 2D vortex dynamics has been probed using mutual inductance and flux noise measurements on YBa2Cu3O7 (YBCO) and MgB2 thin films in zero and low magnetic fields. In such measurements, information about vortex correlations is obtained through a temperature dependent characteristic frequency, below (above) which the vortex movements are uncorrelated (correlated). The results obtained in zero magnetic field indicate that sample heterogeneities influence the vortex physics and hinder the divergence of the vortex-antivortex correlation length.
In low magnetic fields the vortex dynamics is strongly dependent on the applied magnetic field and a power law dependence of the characteristic frequency with respect to the magnetic field is observed. The results indicate that there is a co-existence of thermally and field generated vortices.
The I–V characteristics of untwinned YBCO single crystals show that only a small broadening of the transition region influences the length scale over which the vortex movements are correlated. The dynamic and static critical exponents therefore exhibit values being larger in magnitude as compared to values predicted by relevant theoretical models. The results also suggest that the copper oxide planes in YBCO decouple slightly below the mean field critical temperature and hence, the system has a crossover from 3D to 2D behaviour as the temperature is increased.
From temperature dependent DC-magnetisation measurements performed on untwinned YBCO single crystals in weak applied fields, detailed information about the critical current density and the irreversibility line is obtained.