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Book
Symmetries in Fundamental Physics
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ISBN: 940077642X Year: 2014 Publisher: Dordrecht : Springer Netherlands : Imprint: Springer,

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Abstract

Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P. Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also understand the implications of quantum physics and symmetry considerations: Poincare invariance dictates both the characteristic properties of particles (mass, spin, ...) and the wave equations of spin 0, 1/2, 1, ... objects. Further, the work of C.N. Yang and R. Mills reveals the consequences of internal symmetries as exemplified in the symmetry group of elementary particle physics.  Given this pivotal role of symmetries it is thus not surprising that current research in fundamental physics is to a great degree motivated and inspired by considerations of symmetry. The treatment of symmetries in this monograph ranges from classical physics to now well-established theories of fundamental interactions, to the latest research on unified theories and quantum gravity.


Dissertation
Multiferroic and magnetoelectric properties of Co-implanted ZnO thin films
Authors: ---
ISBN: 9789086497393 Year: 2014 Publisher: Leuven Katholieke Universiteit Leuven

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The study of multiferroics and in particular the magnetoelectric couplin g is nowadays a new focus among the many hot topics in physics. The prom ising future of multiferroic materials lies in the coexistence of tradit ionally uncorrelated properties and the existence of a sizable coupling between them. Multiferroics provide a possibility to control one primary order by means of another primary order and create devices that are sui table for special conditions or can create multifunctionality. However, it is difficult to find multiferroicity due to the incompatiblity of fer romagnetism and ferroelectricity. The mechanism to establish magnetoelec tric coupling is always exotic and varying. Although there have been imp ortant research findings in multiferroics, such as lone-pair based multi ferroics, spin-driven ferroelectricity and multiferroic composites, etc, the field is far from mature yet, and the limitations lie both in the f abrication process as well as the complex measurement methods for charac terizing the magnetoelectrical properties. In this thesis, we achieved a structure consisting of Co atoms and Co na noparticles embedded in a crystalline ZnO thin film, aiming at finding m ultiferroicity and novel magnetotransport in such a nanocomposite system . We fabricated the system by pulsed laser deposition of ZnO followed by high-fluence Co ion implantation. The structural properties were charac terized by X-ray diffraction, transmission electron microscopy and X-ray absorption fine structure measurements. The majority of Co exists in th e matrix in an oxidized state (i.e. can be treated as a so-called (Zn,Co )O matrix). On the other hand, crystallized nanosize Co particles were f ound to be embedded in the (Zn,Co)O thin films, in which the thin film s till keeps good crystallinity. In such a complex nanocomposite system, t he electrical properties were studied by means of a helium-4 flow cryost at with a superconducting magnet down to 2.5 K. The low-temperature resi stance of the films followed the Efros-Shklovskii type variable-range-ho pping. Magnetoresistance revealed a spin-dependent signature that surviv es up to 250 K. Negative magnetoresistance exceeding 10% was observed at a magnetic field of 1 T. The magnetic properties were characterized by superconducting quantum interference device magnetometry. The composite reveals a characteristic superparamagnetic behavior, which is consistent with the presence of metallic Co nanoparticles. In addition, in some ca ses we observed exchange bias in the ZnO-Co system. This exchange bias e ffect constitutes, to the best of our knowledge, the first time observat ion of this effect in the ZnO-Co system. Temperature dependent dielectric constant measurements revealed relaxor ferroelectricity, which was further confirmed by polarization measuremen ts. The combination of the polarization measurement with a cryomagnetic system allowed us to determine the magnetoelectric coupling properties. A remarkable magnetoelectric coupling showed up when measuring the polar ization curve under an applied magnetic field. The unexpected relaxor fe rroelectricty is believed to be the result of the local lattice distorti on induced by the incorporation of the Co nanoparticles.


Dissertation
Ionic liquid technology in metal refining : dissolution of metal oxides and separation by solvent extraction
Authors: ---
ISBN: 9789086496884 Year: 2014 Publisher: Leuven Katholieke Universiteit Leuven

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It goes without saying that point defects play a crucial role in semiconductors, either benificial or detrimental. Introduced as dopants, they ‘define’ one of the most typical electrical characteristics of semiconductors. But often, point defects - mostly intrinsic ones -may play a most detrimental role such as encountered at semiconductor/insulator interfaces where they may be at the origin of an untolerable amount of interface traps and/or recombination centers. As stated, it points to inadequate interface passivation. This makes the study of point defects an indispensible part of bulk semiconductor andsemiconductor/interface science. The current work fits within the latter prospect, where in a fundamental approach, the conventional electron spin resonance (ESR) technique is applied to attempt atomic identification of crucial device-impacting point defects. By means of multi-frequency ESR study, this work is concerned with point defects in ZnS:Mn nanowires, IIIV semiconductor GaAs/oxide entities, and (100)Si/oxide structures with oxides of low dielectric constant . In the first part, multi-frequency ESR and electron spectroscopy techniques were combined to study the symmetry and electronic structures of Mn2+ dopants in solvothermally synthesized c-ZnS nanowires (average diameter 5 nm and 10 nm) with mixed hexagonal and cubic stacking structures. Three different symmetry sites for incorporation of Mn2+ in ZnS have been identified, i.e., substitutional, interstitial/surface sites, and Mn clusters at the surface. Quantum confinement effects are observed, the data indicating a drastically higher efficiency of Mn2+ substitution in large diameter nanowires. The major part of this work has focused on the study of inherently generated interface defects during thermal oxidation of GaAs aiming to assess the atomic-structural identity. The study has been carried out on (100)GaAs/native oxide structures thermally grown in the range Tox = 350-615 oC on both powders and slices of semi-insulating (100)GaAs. Generally, four types of ESR signals (defects) are observed.The first major one is undubiously identified as the As antisite defect which upon oxidation is seen, from Tox = 350 °C onward to be generated in densities increasing with Tox reaching alarmingly high levels (~ 1013 cm-2). This compellingly reveals substantial generation of interfacial 75As+Ga antisites in registry with the GaAs substrate layer, thus providing solid independent evidence of substantial interfacial As enrichment, appearing as endemic to oxidation of GaAs, and at the same time providing an answerof how a major part of excess As gets interfacially incorporated. Given the known electrical deep double donor attribute of As+Ga, direct identification is thus established of a major system of detrimental interface traps, well fit to cause Fermi level pinning. As to technological relevance, it indicates thatoxidation of the GaAs substrate should be efficiently avoided, or if occurred, the impact of it should be strictly removed when aiming realization of device-grade semiconductor/insulator interfaces.A second spectrum, observed in oxidized c-GaAs slices after additional VUV irradiation, is composed of a quartet, centered at gc 2.268 for the applied field direction in the (100)GaAs sample plane, and shows distinct anisotropic behavior; this newly observed spectrum is suggested to concern a VGa in GaAs. Two more isotropic signals are observed at g 2.06 and 1.937. However, in absence of any attendant resolved hyperfine structure, no atomic model can be proposed. Finally, also observed is the spectrum from substitutional Fe3+ ions introduced as compensation dopants (deep acceptors) in the semi-insulating parent GaAs substrate, of which the inferred crystal field data are found to comply will with previous results. The next part of the work deals with the study of CZ-(100)Si/insulator structures with organosilicate films of low dielectric constant grown at 300 oC. This deals with the observation of the NL8 ESR spectrum of C2v symmetry defect &#8722;a thermal double donor, which is found to be introduced in the c-Si substrate during a short UV-assisted thermal curing treatment at 430 oC. A remarkable non-uniform (in depth) generation profile is observed which is concluded as being associated with interface stress. Theresults provide a different and affirmative illustration of the influence of in situ strain during the formation of thermal donors during thermal treatment. The result points to the presence of substantial interface stress.


Book
Symmetries in Fundamental Physics
Author:
ISBN: 3319065815 3319065807 Year: 2014 Publisher: Cham : Springer International Publishing : Imprint: Springer,

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Abstract

Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P.Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also understand the implications of quantum physics and symmetry considerations: Poincare invariance dictates both the characteristic properties of particles (mass, spin, ...) and the wave equations of spin 0, 1/2, 1, ... objects. Further, the work of C.N.Yang and R.Mills reveals the consequences of internal symmetries as exemplified in the symmetry group of elementary particle physics. Given this pivotal role of symmetries it is thus not surprising that current research in fundamental physics is to a great degree motivated and inspired by considerations of symmetry.The treatment of symmetries in this monograph ranges from classical physics to now well-established theories of fundamental interactions, to the latest research on unified theories and quantum gravity.


Book
Irreversibility and Dissipation in Microscopic Systems
Author:
ISBN: 3319070797 3319070789 1322136238 Year: 2014 Publisher: Cham : Springer International Publishing : Imprint: Springer,

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After an insightful introductory part on recent developments in the thermodynamics of small systems, the author presents his contribution to a long-standing problem, namely the connection between irreversibility and dissipation. He develops a method based on recent results on fluctuation theorems that is able to estimate dissipation using only information acquired in a single, sufficiently long, trajectory of a stationary nonequilibrium process. This part ends with a remarkable application of the method to the analysis of biological data, in this case, the fluctuations of a hair bundle. The third part studies the energetics of systems that undergo symmetry breaking transitions. These theoretical ideas lead to, among other things, an experimental realization of a Szilard engine using manipulated colloids. This work has the potential for important applications ranging from the analysis of biological media to the design of novel artificial nano-machines.


Book
Entransy in Phase-Change Systems
Authors: ---
ISBN: 3319074288 331907427X 1322136661 Year: 2014 Publisher: Cham : Springer International Publishing : Imprint: Springer,

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Entransy in Phase-Change Systems summarizes recent developments in the area of entransy, especially on phase-change processes. This book covers new developments in the area including the great potential for energy saving for process industries, decreasing carbon dioxide emissions, reducing energy bills and improving overall efficiency of systems. This concise volume is an ideal book for engineers and scientists in energy-related industries.


Book
Experiments and Numerical Simulations of Turbulent Combustion of Diluted Sprays : TCS 3: Third International Workshop on Turbulent Spray Combustion
Authors: ---
ISBN: 3319046780 3319046772 Year: 2014 Publisher: Cham : Springer International Publishing : Imprint: Springer,

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This book reflects the results of the 2nd and 3rd International Workshops on Turbulent Spray Combustion. The focus is on progress in experiments and numerical simulations for two-phase flows, with emphasis on spray combustion. Knowledge of the dominant phenomena and their interactions allows development of predictive models and their use in combustor and gas turbine design. Experts and young researchers present the state-of-the-art results, report on the latest developments and exchange ideas in the areas of experiments, modelling and simulation of reactive multiphase flows. The first chapter reflects on flame structure, auto-ignition and atomization with reference to well-characterized burners, to be implemented by modellers with relative ease. The second chapter presents an overview of first simulation results on target test cases, developed at the occasion of the 1st International Workshop on Turbulent Spray Combustion. In the third chapter, evaporation rate modelling aspects are covered, while the fourth chapter deals with evaporation effects in the context of flamelet models. In chapter five, LES simulation results are discussed for variable fuel and mass loading. The final chapter discusses PDF modelling of turbulent spray combustion. In short, the contributions in this book are highly valuable for the research community in this field, providing in-depth insight into some of the many aspects of dilute turbulent spray combustion.


Book
Nonlinear analysis of gas-water/oil-water two-phase flow in complex networks
Authors: --- ---
ISBN: 3642383726 3642383734 Year: 2014 Publisher: Heidelberg [Germany] : Springer,

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Understanding the dynamics of multi-phase flows has been a challenge in the fields of nonlinear dynamics and fluid mechanics. This chapter reviews our work on two-phase flow dynamics in combination with complex network theory. We systematically carried out gas-water/oil-water two-phase flow experiments for measuring the time series of flow signals which is studied in terms of the mapping from time series to complex networks. Three network mapping methods were proposed for the analysis and identification of flow patterns, i.e. Flow Pattern Complex Network (FPCN), Fluid Dynamic Complex Network (FDCN) and Fluid Structure Complex Network (FSCN). Through detecting the community structure of FPCN based on K-means clustering, distinct flow patterns can be successfully distinguished and identified. A number of FDCN’s under different flow conditions were constructed in order to reveal the dynamical characteristics of two-phase flows. The FDCNs exhibit universal power-law degree distributions. The power-law exponent and the network information entropy are sensitive to the transition among different flow patterns, which can be used to characterize nonlinear dynamics of the two-phase flow. FSCNs were constructed in the phase space through a general approach that we introduced. The statistical properties of FSCN can provide quantitative insight into the fluid structure of two-phase flow. These interesting and significant findings suggest that complex networks can be a potentially powerful tool for uncovering the nonlinear dynamics of two-phase flows.


Book
Lived diversities : space, place and identities in the multi-ethnic city
Authors: --- --- ---
ISBN: 9781447315643 1447315642 1322177767 144732112X 1447315715 1447315650 1447315855 9781447315650 9781322177762 9781447315858 Year: 2014 Publisher: Bristol : Policy Press,

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Focusing on multi-ethnic interaction in an inner city area, this book addresses difficult issues that are often simplistically and negatively portrayed, challenging the stereotypical denigration of inner city life, and Muslim communities in particular.

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