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Ferromagnetic manganites: spin-polarized conduction and competing interactionsDörr, Kathrin 29 October 2007 (has links) (PDF)
Electronic properties of solids are vitally important for modern technology, one may think of microelectronics, magnetic data storage, communication technologies and others. Sometimes, it seems possible to postpone the step of fundamental understanding when starting the application of a new material. However, lasting success and discovery of principally new approaches is based on it ...
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Simulation of Weakly Correlated Functions and its Application to Random Surfaces and Random PolynomialsFellenberg, Benno, Scheidt, Jürgen vom, Richter, Matthias 30 October 1998 (has links) (PDF)
The paper is dedicated to the modeling and the
simulation of random processes and fields.
Using the concept and the theory of weakly
correlated functions a consistent representation
of sufficiently smooth random processes
will be derived. Special applications will be
given with respect to the simulation of road
surfaces in vehicle dynamics and to the
confirmation of theoretical results with
respect to the zeros of random polynomials.
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Zeitaufgelöste Mikroskopie an einzelnen Molekülen zur Untersuchung der Polymerdynamik in dünnen FilmenSchmidt, Ruben 30 March 2006 (has links) (PDF)
Gegenstand dieser Diplomarbeit ist die Untersuchung der Dynamik in dünnen Polymerfilmen anhand von einzelnen Molekülen. Zu diesem Zweck wurden dünne Filme (kleiner 100nm) hergestellt und mittels Einzelmoleküldetektion und zeitaufgelöster Einzelphotonenzählung analysiert, was eine orts- und zeitaufgelöste Untersuchung einzelner Farbstoffmoleküle ermöglicht.
Ziel war es, festzustellen ob, und auf welchem Weg, die Dynamik der Umgebung in Fluktuationen der Fluoreszenzlebensdauer einzelner Moleküle sichtbar wird.
Neben der Evaluierung der Untersuchungsmethoden wurden in dieser Arbeit zwei Arten von Sensormolekülen - DiD und Malachit Grün - näher untersucht. / The subject of this diploma thesis is the analysis of dynamics in thin polymer films using single molecules. Thin polymer films (less than 100nm) were produced and analysed by Single Molecule Detection (SMD) and Time Correlated Single Photon Counting (TCSPC). This allows a spatial and time resolved investigation of the single dye molecule.
The aim was to ascertain if, and in which way, the dynamics of the environment are reflected by fluctuations of the fluorescence lifetime of the single molecule.
In addition to evaluating the investigation methods two kinds of molecules - DiD and Malachite Green - were also analysed.
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Oxide Thermoelectrics: The Role of Crystal Structure on Thermopower in Strongly Correlated SpinelsSparks, Taylor David 10 August 2012 (has links)
This dissertation reports on the synthesis, structural and thermal characterization and electrical and thermal transport properties of a variety of strongly correlated spinels. General structure property relationships for electrical and thermal transport are discussed. However, the relationship between thermopower and features of the crystal structure such as spin, crystal field, anti-site disorder, and structural distortions are explored in depth. The experimental findings are reported in the context of improving existing oxide thermoelectric materials, screening for new materials or using thermopower as a unique characterization tool to determine the cation distribution in spinels. The need for improved n-type oxide thermoelectric materials has led researchers to consider mixed valence \((+3/+4)\) manganese oxides. Contrary to previous findings we report herein that the \(LiMn_2O_4\) compound reaches the relatively large n-type thermopower of \(-73 \mu V/K\) which is three times larger than the value observed in other manganese oxides, \(-25 \mu V/K\). The cause of this increase in thermopower is shown to be the absence of a Jahn-Teller distortion on the \(Mn^{3+}\) ions in \(LiMn_2O_4\). By avoiding this structural distortion the orbital degeneracy is doubled and the Koshibae et al.’s modified Heikes formula predicts a thermopower of \(-79 \mu V/K\) in good agreement with the experiment. Altering the \(Mn^{3+/4+}\) ratio via aliovalent doping did not affect the thermopower and is a second evidence of universal charge transport first reported by Kobayashi et al. The role of anti-site disorder was further examined in \(Fe_xMn_{1-x}NiCrO_4\) x=0, ½, ¾, 1 spinels but the effect on thermopower was inconclusive due to the presence of impurity phases. Next, the thermopower as a function of temperature in \(Co_3O_4\) was investigated as a means whereby the Wu and Mason’s 30 year old model for using thermopower to calculate cation distribution in spinels could be revisited. We report evidence that Wu and Mason’s original model using the standard Heikes formula and considering octahedral sites alone leads to a stoichiometrically inconsistent result at high temperatures. Alternate models are evaluated considering Koshibae et al.’s modified Heikes formula and accounting for tetrahedral site contributions. Furthermore, the effect of a possible spin state transition is considered. / Engineering and Applied Sciences
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An Empirical Analysis of Publicity and Advertising under Quality UncertaintyLim, Hyunwoo 17 December 2012 (has links)
Quality of a prescription drug is uncertain to patients, physicians and even the manufacturer of the drug. Because this uncertainty can deter physicians from prescribing the drug, it is important to investigate how various marketing communication activities help reveal the true quality of its product. In particular, this study investigates publicity and advertising under quality uncertainty. Chapter 1 studies the effect of publicity on consumer demand with a reduced form approach. Chapter 2 structurally investigates the roles of detailing and publicity when the information spill-over is present. Both chapters study the market of anti-cholesterol drugs (statins).
Chapter 1 investigates the effects of publicity (media coverage) on consumer demand. The main obstacle to measuring the impact of publicity is that data on media coverage are difficult to interpret. To overcome this obstacle, we propose a new way to code information presented in news articles, mapping the information to a multi-dimensional attribute space. We combine our publicity data with data on sales, detailing, medical journal advertising, direct-to-consumer advertising (DTCA) and landmark clinical trial outcomes, and estimate a demand model. Our results suggest that not all forms of publicity are equal.
In chapter 2, we study consumer learning about scientific evidence and its impact on demand for pharmaceutical products by using the Bayesian learning model. Unlike previous literature, our learning model allows consumer’s prior quality perceptions to be correlated across brands. This unique feature of the model allows us to investigate information spill-over effects across brands. The information spill-over allows late entrants to free-ride on first movers’ investment in clinical trials and marketing activities and to gain late mover advantage. In addition to using product level market share data, we supplement them with switching rates and discontinuing rates. The switching rate data are particularly useful for taking the presence of switching costs into consideration, which has been ignored in the literature using product-level data. Our estimated structural model has implications for managers in allocating resources to various types of marketing activities more efficiently and helps forecast returns of clinical trials that are sponsored by pharmaceutical firms.
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Krepšinio rungtynių rezultatų analizės metodai / Analysis methods of basketball game resultsMorkūnas, Gintaras 26 May 2006 (has links)
Sports are getting more and more benefit from use of information technologies. Information technologies can provide not only collected sport event statistics but also can give more complex analysis results that can be used for planning sport strategies and tactics. Also information technologies are used in sports monitoring, data gathering and result data analysis. Great results are achieved in basketball monitoring and data analysis. Most popular and widely used basketball data analysis methods are rating systems. Other analysis methods can provide predictions on forthcoming basketball games. With aim to provide new possibilities in data analysis area some popular basketball data analysis methods are introduced with discussed possibilities of methods improvements. As a research result possibilities for basketball rating systems improvements are proposed. Also framework for basketball games prediction methods precision research is designed and developed. Using developed framework prediction methods are researched and main results provided.
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Analysis of Functional Models in Density Functional Theory : Applications to Transition Metal Oxides2013 September 1900 (has links)
This work presents a study of the electronic structure of four transition metal oxides (TMOs) using spectroscopic data and a variety of theoretical models. TMOs are a class of materials made from d-block metals in the periodic table, and one or more oxygen atoms. The nature of d-electrons is examined and theoretical models used to treat d-electron systems are tested against experimental data.
Background theory of condensed matter physics is outlined. An overview of density functional theory (DFT) as a theoretical model for calculating the electronic structure of materials is presented. A variety of exchange-correlation (XC) functionals used within the DFT framework are outlined and tested for their applicability to the TMO systems in question. X-ray spectroscopy is briefly outlined and used to test the validity of the different XC functionals.
All four compounds, AgO, Ag2O, CuO, and Cu2O require a Hubbard U term in the XC functional to most accurately reproduce experimental results. The effects of varying the value of U is examined in depth. The oxygen K-edge X-ray emission spectra (XES) exhibits a“two peak” structure for all compounds; the effect of varying the U value is to change the intensity ratio of the two peaks. The ratio of the two peaks as a function of U shows a linear trend in all compounds. A simple line is fit to the peak ratio vs. U curve. A common line between all compounds would provide an important metric with which to predict the appropriate U value needed in similar materials based on simple experimental data. However, the parameters of the fitted line were not common between the four compounds and any metric derived from this method would be system-dependent and not widely applicable to other systems. There are, however, interesting trends in the data when the U value is varied that provide subjects for future research.
A number of fundamental quantities are determined both from experiment and theoretical calculations. Calculated bandgap values are shown to be lower than the experimental values for most functionals tested. This is not unexpected as DFT methods are known to predict much smaller bandgaps than expected. The Heyd-Scuseria-Ernzerhof (HSE) functional used for Ag2O and Cu2O does predict the bandgaps very accurately. The core-hole effect is estimated and proven to be negligible in these systems. Charge transfer and on-site Coulomb repulsion energies, important quantities in the electronic behaviour of TMOs, are determined and compared to previously reported values.
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Proof system for logic of correlated knowledge / Įrodymų sistema koreliatyvių žinių logikaiGiedra, Haroldas 30 December 2014 (has links)
Automated proof system for logic of correlated knowledge is presented in the dissertation. The system consists of the sequent calculus GS-LCK and the proof search procedure GS-LCK-PROC. Sequent calculus is sound, complete and satisfy the properties of invertibility of rules, admissibility of weakening, contraction and cut. The procedure GS-LCK-PROC is terminating and allows to check if the sequent is provable. Also decidability of logic of correlated knowledge has been proved. Using the terminating procedure GS-LCK-PROC the validity of all formulas of logic of correlated knowledge can be checked. / Automatinė įrodymų sistema koreliatyvių žinių logikai yra pristatoma disertacijoje. Sistemą sudaro sekvencinis skaičiavimas GS-LCK ir įrodymo paieškos procedūra GS-LCK-PROC. Sekvencinis skaičiavimas yra pagrįstas, pilnas ir tenkina taisyklių apverčiamumo, silpninimo, prastinimo ir pjūvio leistinumo savybes. Procedūra GS-LCK-PROC yra baigtinė ir leidžia patikrinti, ar sekvencija yra išvedama. Taip pat buvo įrodytas koreliatyvių žinių logikos išsprendžiamumas. Naudojant baigtinę procedūra GS-LCK-PROC, visų koreliatyvių žinių logikos formulių tapatus teisingumas gali būti patikrintas.
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An Empirical Analysis of Publicity and Advertising under Quality UncertaintyLim, Hyunwoo 17 December 2012 (has links)
Quality of a prescription drug is uncertain to patients, physicians and even the manufacturer of the drug. Because this uncertainty can deter physicians from prescribing the drug, it is important to investigate how various marketing communication activities help reveal the true quality of its product. In particular, this study investigates publicity and advertising under quality uncertainty. Chapter 1 studies the effect of publicity on consumer demand with a reduced form approach. Chapter 2 structurally investigates the roles of detailing and publicity when the information spill-over is present. Both chapters study the market of anti-cholesterol drugs (statins).
Chapter 1 investigates the effects of publicity (media coverage) on consumer demand. The main obstacle to measuring the impact of publicity is that data on media coverage are difficult to interpret. To overcome this obstacle, we propose a new way to code information presented in news articles, mapping the information to a multi-dimensional attribute space. We combine our publicity data with data on sales, detailing, medical journal advertising, direct-to-consumer advertising (DTCA) and landmark clinical trial outcomes, and estimate a demand model. Our results suggest that not all forms of publicity are equal.
In chapter 2, we study consumer learning about scientific evidence and its impact on demand for pharmaceutical products by using the Bayesian learning model. Unlike previous literature, our learning model allows consumer’s prior quality perceptions to be correlated across brands. This unique feature of the model allows us to investigate information spill-over effects across brands. The information spill-over allows late entrants to free-ride on first movers’ investment in clinical trials and marketing activities and to gain late mover advantage. In addition to using product level market share data, we supplement them with switching rates and discontinuing rates. The switching rate data are particularly useful for taking the presence of switching costs into consideration, which has been ignored in the literature using product-level data. Our estimated structural model has implications for managers in allocating resources to various types of marketing activities more efficiently and helps forecast returns of clinical trials that are sponsored by pharmaceutical firms.
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Quantum Circuit Based on Electron Spins in Semiconductor Quantum DotsHsieh, Chang-Yu 07 March 2012 (has links)
In this thesis, I present a microscopic theory of quantum circuits based on interacting electron spins in quantum dot molecules. We use the Linear Combination of Harmonic Orbitals-Configuration Interaction (LCHO-CI) formalism for microscopic calculations. We then derive effective Hubbard, t-J, and Heisenberg models. These models are used to predict the electronic, spin and transport properties of a triple quantum dot molecule (TQDM) as a function of topology, gate configuration, bias and magnetic field.
With these theoretical tools and fully characterized TQDMs, we propose the following applications:
1. Voltage tunable qubit encoded in the chiral states of a half-filled TQDM. We show how to perform single qubit operations by pulsing voltages. We propose the "chirality-to-charge" conversion as the measurement scheme and demonstrate the robustness of the chirality-encoded qubit due to charge fluctuations. We derive an effective qubit-qubit Hamiltonian and demonstrate the two-qubit gate. This provides all the necessary operations for a quantum computer built with chirality-encoded qubits.
2. Berry's phase. We explore the prospect of geometric quantum computing with chirality-encoded qubit. We construct a Herzberg circuit in the voltage space and show the accumulation of Berry's phase.
3. Macroscopic quantum states on a semiconductor chip. We consider a linear chain of TQDMs, each with 4 electrons, obtained by nanostructuring a metallic gate in a field effect transistor. We theoretically show that the low energy spectrum of the chain maps onto that of a spin-1 chain. Hence, we show that macroscopic quantum states, protected by a Haldane gap from the continuum, emerge.
In order to minimize decoherence of electron spin qubits, we consider using electron spins in the p orbitals of the valence band (valence holes) as qubits. We develop a theory of valence hole qubit within the 4-band k.p model. We show that static magnetic fields can be used to perform single qubit operations. We also show that the qubit-qubit interactions are sensitive to the geometry of a quantum dot network. For vertical qubit arrays, we predict that there exists an optimal qubit separation suitable for the voltage control of qubit-qubit interactions.
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