Neste trabalho, foram desenvolvidos e implementados três métodos experimentais, o método de corrente constante - CC (adaptado a partir do triodo de corona à corrente constante), o método de rampa de tensão - RT (adaptado a partir do método bipolar de medida de histerese elétrica) e o método para medida do coeficiente piroelémco pela técnica da temperatura oscilante (função senoidal). Os métodos foram empregados no estudo das polarizações elétricas apresentadas pelo PVDF, PVF, o copolímero P(VDF-TrFE) e a blenda P(VDF-TrFE) - PMMA. Verificou-se através de medidas de difratometia de raios-x, medida da polarização ferroelétrica (obtida pelos métodos CC e RT) e medida do coeficiente piroelétrico que parte da polarização elétrica relaxa após a remoção do campo elétrico e está associada a efeitos não hereditários. Foi estudada a dependência desta polarização com o campo elétrico aplicado (taxa de subida do campo e campo máximo), com o tempo de curto circuito que a amostra foi submetida entre processos de polarização consecutivos e o tipo de amostra. Foram determinados e comparados a polarização remanescente e o campo coercitivo dos materiais citados, obtidos pelos métodos CC e RT. / In this work three experimental setups were developed, the constant current method (CC) (derived from the corona mode with constant current), the ramp voltage method (RT) (derived from the bipolar hysteresis measurements) and measurement of the pyroeletric coefficient employing a sinusoidal temperature variation. These methods were used to study the ferroelectric polarization in polymers such as PVDF, PVF, copolymer of P(VDF-TrFE) and P(VDF-TrFE) - PMMA blend. From x-ray, electric polarization and pyroelectric measurements it was found that part of the total polarization decays after removing the electric field. The dependence of such decaying polarization on the rate of increasing of the electric field, on the maximum field applied to the sample and the time interval of short-circuit between successive measurements was investigated. The value of the remanent polarization and the coercive field was determined for polymeric materials listed above and a comparison of the results obtained using the CC and RT method was performed.

Poon, Sin Yau = 光子在噪聲環境中的解糾纏 / 潘善柔. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 101-110). / Abstracts in English and Chinese. / Poon, Sin Yau = Guang zi zai zao sheng huan jing zhong de jie jiu chan / Pan Shanrou. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Review on entanglement theory --- p.4 / Chapter 2.1 --- Pure state entanglement --- p.4 / Chapter 2.2 --- Mixed state entanglement --- p.7 / Chapter 2.3 --- Positive partial transposition (PPT) criterion --- p.9 / Chapter 2.4 --- Negativity of pTA --- p.9 / Chapter 2.4.1 --- Basic properties --- p.10 / Chapter 2.4.2 --- Comparison with concurrence --- p.11 / Chapter 2.5 --- Entanglement witness --- p.12 / Chapter 2.6 --- Inseparability criterion based on uncertainty relations --- p.13 / Chapter 2.7 --- Limitations of the PPT criterion --- p.14 / Chapter 2.8 --- Other manifestations of entanglement --- p.16 / Chapter 2.8.1 --- Non-classicality by negative P-representation --- p.16 / Chapter 2.8.2 --- Non-locality by violation of Bell´ةs inequality --- p.17 / Chapter 3 --- Quantum decoherence: General considerations for open systems --- p.22 / Chapter 3.1 --- A master equation approach --- p.22 / Chapter 3.1.1 --- Master equation in Markovian channels --- p.25 / Chapter 3.2 --- Negativity as a monotone in Markovian systems --- p.26 / Chapter 3.3 --- Finite time disentanglement --- p.29 / Chapter 3.4 --- Non-classicality of harmonic oscillating systems in finite temperature baths --- p.32 / Chapter 4 --- Disentanglement dynamics of two-mode Gaussian states --- p.36 / Chapter 4.1 --- Two-mode Gaussian states: General descriptions --- p.36 / Chapter 4.1.1 --- Covariance matrices and symplectic eigenvalues --- p.37 / Chapter 4.1.2 --- Squeezed states as a source of entanglement --- p.39 / Chapter 4.2 --- Eigenvalues and eigenvectors of pTA --- p.41 / Chapter 4.3 --- Physical interpretation of negativity --- p.43 / Chapter 4.4 --- Disentanglement of two-mode squeezed states in damping and amplifying environment --- p.47 / Chapter 4.4.1 --- Block structures of pTA in Fock space --- p.47 / Chapter 4.4.2 --- Analytic solution of p in position space --- p.49 / Chapter 4.4.3 --- Evolution of eigenvalues and eigenvectors of pTA --- p.51 / Chapter 4.4.4 --- Robust structure of entanglement witness --- p.56 / Chapter 4.5 --- Beam splitter as a model for thermal damping of initial Gaussian states --- p.59 / Chapter 4.6 --- Evolution of entanglement of a damped parametric oscillator --- p.63 / Chapter 4.6.1 --- Eigenvalues and Eigenvectors of pTA --- p.64 / Chapter 4.6.2 --- Negativity and sub-negativity --- p.66 / Chapter 4.7 --- Dissipation in baths with both amplitude and phase damping --- p.68 / Chapter 4.8 --- Loss of nonlocality: An optimized Bell's inequality approach --- p.69 / Chapter 5 --- Disentanglement via polarization mode dispersion --- p.73 / Chapter 5.1 --- Review on polarization mode dispersion --- p.73 / Chapter 5.2 --- A model for stochastic polarization mode dispersion --- p.75 / Chapter 5.3 --- General description of two-photon states --- p.78 / Chapter 5.4 --- Disentanglement of two-photon states in separate fibers --- p.81 / Chapter 5.4.1 --- Polarization negativity and frequency negativity --- p.83 / Chapter 5.4.2 --- Polarization disentanglement --- p.84 / Chapter 5.4.3 --- Frequency disentanglement --- p.85 / Chapter 5.5 --- Disentanglement of two-photon states in a common fiber --- p.86 / Chapter 5.5.1 --- Polarization disentanglement of the singlet state --- p.90 / Chapter 5.5.2 --- Frequency entanglement of the singlet state --- p.91 / Chapter 5.6 --- Non-Markovian channels --- p.92 / Chapter 6 --- Conclusion --- p.99 / Bibliography --- p.101 / Chapter A --- CHSH Inequality for bipartite two level systems --- p.111 / Chapter B --- Transformation from general two-mode Gaussian to double Gaussian product --- p.113 / Chapter C --- Time evolution of general real symmetric two-mode Gaussian density operator --- p.116 / Chapter D --- Time evolution of a damped parametric oscillator --- p.119 / Chapter E --- Optimal Bell values for a damped TMSV in pseudo-spin formalism --- p.123 / Chapter F --- Derivation of master equation for two-photon states --- p.125 / Chapter G --- Solution of master equation for two-photon states --- p.127 / Chapter G.1 --- Evolution of two-photon states in separate fibers --- p.127 / Chapter G.2 --- Evolution of two-photon state in a common fiber --- p.129

abstract: This dissertation consists of three essays on modern economic growth and structural transformation, in particular touching on the reallocation of labor across industries, occupations, and employment statuses. The first chapter investigates the quantitative importance of non-employment in the labor market outcomes for the United States. During the last 50 years, production has shifted from goods to services. In terms of occupations, the routine employment share decreased, giving way to increases in manual and abstract ones. These two patterns are related, and lower non-employment had an important role. A labor allocation model where goods, market services, and home services use different tasks as inputs is used for quantitative exercises. These show that non-employment could significantly slow down polarization and structural transformation, and induce significant displacement within the labor force. The second chapter, coauthored with Bart Hobijn and Todd Schoellman, looks at the demographic structure of structural transformation. More than half of labor reallocation during structural transformation is due to new cohorts disproportionately entering growing industries. This suggests substantial costs to labor reallocation. A model of overlapping generations with life-cycle career choice under switching costs and structural transformation is studied. Switching costs accelerate structural transformation, since forward-looking workers enter growing industries in anticipation of future wage growth. Most of the impact of switching costs shows on relative wages. The third chapter establishes that job polarization is a global phenomenon. The analysis of polarization is extended from a group of developed countries to a sample of 119 economies. At all levels of development, employment shares in routine occupations have decreased since the 1980s. This suggests that routine occupations are becoming increasingly obsolete throughout the world, rather than being outsourced to developing countries. A development accounting framework with technical change at the \textit{task} level is proposed. This allows to quantify and extrapolate task-specific productivity levels. Recent technological change is biased against routine occupations and in favor of manual occupations. This implies that in the following decades, world polarization will continue: employment in routine occupations will decrease, and the reallocation will happen mostly from routine to manual occupations, rather than to abstract ones. / Dissertation/Thesis / Doctoral Dissertation Economics 2019

Using data from the American National Election Studies from 1968 to 2016, I explore the historical relationship between voter income, other demographic factors, and political polarization. I find that while having a higher income and a better education generally correlates with increased Republican political preference, though the relationship between higher income and increased Republican preference does not hold in lower income groups. Race is by far the most significant indicator of political preference, with whites and blacks on opposite ends of the political spectrum, and Hispanics as well as other races somewhere in between the two. In addition, I analyze the data from 20th century elections separately from 21st century elections and discover key differences in how each factor influences political preference.

Hydrogen gas is the cleanest fuel which produces only water as a combustion product with no greenhouse or toxic gases. The combustible hydrogen fuel is an energy carrier but not an energy source. As an element, hydrogen is widely available in nature as a component of water and of hydrocarbons. An energy source is needed to extract the element from these compounds and convert it to the combustible hydrogen gas. Today, the energy source for nearly all hydrogen production is fossil fuel, principally natural gas. The supply of natural gas is limited and its price is increasing. Greenhouse gas and air pollutants are emitted when natural gas is used. Electrolytic extraction of hydrogen from water can overcome these stated problems but is more expensive with the present price of natural gas. Manufacturing the hydrogen with a valuable co-product would address this cost disadvantage. Sulfuric acid is a valuable chemical that is produced in large quantities. This research project helps to develop a procedure for extracting hydrogen from water while producing sulfuric acid as a co-product. An electrochemical cell was designed and developed for the production of hydrogen which uses sulfuric acid as electrolyte. In this electrochemical cell with sulfuric acid as an electrolyte we produce hydrogen at the negative electrode while the positive electrode is bathed in sulfur dioxide which it oxidizes to sulfuric acid. The sulfuric acid is collected at the bottom of the cell as valuable co-product. The presence of SO2 to scavenge the anode substantially reduces the equilibrium voltage required for the direct dissociation of water into hydrogen and oxygen. Various design parameters and the fabrication of the reactor are discussed briefly in the thesis. Experimental results of hydrogen production and current voltage curves are discussed. Sulfuric acid corrosion of cell materials is also discussed.

<p>Localization and magnetic properties of electrons in a thin, cyclic quasi one-dimensional GaAs wire with a central potential barrier were studied using the Hartree-Fock and LSDA (Local Spin Density Approximation, exchange only) and compared to more time consuming Quantum Monte-Carlo calculations. Within LSDA, evidence of true localization was found as well as evidence for the existence of both ferromagnetic as well as anti-ferromagnetic states. Also signs of two-dimensional spin localization was found, without associated localized electrons.</p>

Two-port polarization independent electro-optically wavelength tunable filters based on asymmetric Mach-Zehnder structure in LiNbO3 substrate have been developed for 1.55μm application. The operation principle is based on Mach-Zehnder interference and TE↔TM mode conversion. Fabrication parameters for channel waveguides, interferometers and mode converters have been optimized. 7μm wide single mode straight channel waveguides were produced by diffusing 1050-1100A thick Ti into LiNbO3 substrate. Insertion loss of 3.6dB was achieved for both TE and TM polarization. Mach-Zehnder interferometer performance was optimized by testing the Y-branch on samples cut in half length compared to complete device. Best results were obtained from samples that were produced by diffusion at 1025 degC for 11 hours of 1050A thick Ti film, and by diffusion at 1025 degC for 12 hours of 1090A thick Ti film. Metal electrodes were added to one arm of asymmetric Mach-Zehnder interferometers to evaluate electro-optic modulation. Modulation depth as high as 99.6% for TE mode and 98.9% for TM mode were obtained. TE↔TM mode conversion was demonstrated on straight channel waveguides with conversion efficiency greater than 96% utilizing 500 strain inducing SiO2 grating pads with 21μm spatial period. Two-port polarization independent electro-optically tunable wavelength filters were produced based on the optimized parameters described above. The -3dB bandwidth of the filter is 2.4nm. The nearest side lobe to the main peak is more than 13dB below the central lobe for both TE polarization and TM polarization. A thermal tuning rate of -0.765nm/degC is obtained. An electrical tuning range of 12.8nm and a tuning rate of 0.08nm/V were achieved.

This thesis concerns and combines the results of experimental studies of magnetocaloric, multiferroic and spin-glass materials, using SQUID magnetometry as the main characteriza-tion technique.  The magnetocaloric effect offers an interesting new technology for cooling and heating applications. The studies of magnetocaloric materials in this thesis are focused on experimen-tal characterization of fundamental magnetic properties of Fe2P-based materials. These are promising magnetocaloric materials with potential industrial use. It is found that the magneto-caloric properties of Fe2P can be optimally tuned by substitution of manganese for iron and silicon for phosphorus. Furthermore, a simple device to measure the magnetocaloric effect in terms of the adiabatic temperature change was constructed.  Materials that simultaneously exhibit different types of ferroic order, for example magnetic and electrical order, are rare in nature. Among these multiferroic materials, those in which the ferroelectricity is magnetically-induced, or vice versa the magnetism is electrically-induced, are intensively studied due to a need for new functionalities in future data storage and logic devices. This thesis presents results on two materials: Co3TeO6 and Ba3NbFe3Si2O14, which belong to the group of magnetically-induced ferroelectrics and exhibit strong coupling be-tween the magnetic and the electrical order parameter. Their ordering properties were studied using magnetic and electrical measurement techniques. The coupling between the magnetic and electronic degrees of freedom was investigated using high-field and low-temperature Raman spectroscopy.  Spin-glass materials exhibit complex magnetism and disorder. The influence of the spin dimensionality on the low and high magnetic field properties of spin glasses was investigated by studying model Heisenberg, XY and Ising spin-glass systems. Significant differences were found between the non-equilibrium dynamics and the hysteresis behavior of Heisenberg systems compared to those of XY and Ising spin glasses.

PoGOLite is a balloon-borne experiment, which will study polarized soft γ-ray emissionfrom astrophysical targets in the 25-80 keV energy range by applying well-typephoswich detector technology. Polarized γ-rays are expected from a wide variety of sources including rotation-powered pulsars, accreting black holes and neutron stars,and jet-dominated active galaxies. Polarization measurements provide a powerfulprobe of the γ-ray emission mechanism and the distribution of magnetic and radiation fields around the source. The polarization is determined using Compton scattering and photoelectric absorption in an array of 217 plastic scintillators. The sensitive detector is surrounded by a segmented Bismuth Germanium Oxide (BGO) anticoincidence shield. The function of this shield is to reduce backgrounds from charged cosmic rays, primary and atmospheric γ-rays, and atmospheric and instrumenta lneutrons. The anticoincidence shield consists of 427 BGO crystals with three different geometries. The characteristics of the BGO crystals of the bottom anticoincidence shield have been studied with particular focus on the light yield.The maiden flight of PoGOLite will be with a reduced detector volume “pathfinder” instrument. The flight, lasting about 24 hours, is foreseen from Esrange, Sweden in August 2010. The performance of the pathfinder has been studied using computer simulations. The effect of atmospheric attenuation, both on the signal of theastronomical target and on the background, are studied. These allow an observationstrategy to be developed for the forthcoming flight. A polarization analysis method is described and applied to an observation example. The method sets anupper limit on the accuracy with which the polarimeter will be able to detect polarization the angle and degree. The PoGOLite polarimeter has a relatively small field of view (2.4◦×2.4◦) which must be kept aligned to objects of interest on the sky. A star tracker forms part of the attitude control system. The star trackersystem comprises a CCD camera, a lens, and a baffle system. Preliminary studiesof the star identification performance are presented and are found to be compatible with the environment around the Crab, which is the main observational target for the first flight. / QC20100629

Localization and magnetic properties of electrons in a thin, cyclic quasi one-dimensional GaAs wire with a central potential barrier were studied using the Hartree-Fock and LSDA (Local Spin Density Approximation, exchange only) and compared to more time consuming Quantum Monte-Carlo calculations. Within LSDA, evidence of true localization was found as well as evidence for the existence of both ferromagnetic as well as anti-ferromagnetic states. Also signs of two-dimensional spin localization was found, without associated localized electrons.