Optical resonances in multilayer structures

Theoretical research in optics may be divided in two distinctive but well connected\ud general directions. The first deals with developing new or improving existing mathematical\ud models to describe relevant physics. The second aims to predict new\ud phenomena or applications using established models and techniques. This thesis\ud touches both directions through the study of resonances in optical multilayers.\ud Optical multilayers are structures periodic in their properties in one direction.\ud They have been longstanding subject of investigation. Nonetheless, both fundamental\ud and applied research in multilayer optics is still important due to the relevance\ud of multilayer structures for optical systems. The introduction of specific\ud defects in otherwise periodic configurations enables effective tailoring of the optical\ud transmission properties. Equally important, novel materials give additional\ud degrees of freedom for the implementation of desired functionalities as well as the\ud exploration of new physical phenomena. Besides, knowledge gained from an investigation\ud of multilayer structures may serve as a basis for the interpretation and\ud the qualitative understanding of higher dimensional optical structures

Fluid theory of coherent magnetic vortices in high-beta space plasmas

In-situ observations in the Earth's and Saturn's magnetosheaths and in the solar wind reveal the presence of Alfv\'en vortices as intermittent structures in the range of scales from fluid lengths down to few ion lengths. The density and the magnetic field associated with them appear to be compressible for higher plasma betas. Until now, only incompressible Alfv\'en vortices have been known. Motivated by space plasma observations we develop a new model of magnetic vortices in high-beta plasmas with anisotropic temperature, possessing compressible density and magnetic field, whose typical size ranges from fluid to ion scales. At magneto-fluid scales we find novel non-propagating field-aligned cylindrical monopoles and inclined propagating dipoles. Their transverse magnetic and velocity fluctuations are aligned, but not identical, {and they exhibit density and compressible magnetic field fluctuations $\delta n$ and $\delta B_\Vert$ localized inside the vortex core. In the presence of thermal anisotropy and acoustic effects, they may be correlated or anti-correlated $\delta n/\delta B_\Vert={\rm constant}\gtrless 0$; fluctuations whose velocity along the magnetic field is below the ion thermal speed are always correlated.} At ion or kinetic scales (with the smallest radii $\sim c/\omega_{pi}, \rho_{L i}$) {and in the absence of acoustic perturbations}, only dipolar Alfv\'en vortices survive with similar properties as those at fluid scales, except for their $\delta n/n_0$ that reaches the level of $\delta B_\Vert/B_0$. At kinetic scales we find also pressure balanced dipolar structures, possessing finite parallel electric field $E_\Vert$ and purely compressional magnetic field perturbation

Solar wind turbulent spectrum at plasma kinetic scales

The description of the turbulent spectrum of magnetic fluctuations in the solar wind in the kinetic range of scales is not yet completely established. Here, we perform a statistical study of 100 spectra measured by the STAFF instrument on the Cluster mission, which allows to resolve turbulent fluctuations from ion scales down to a fraction of electron scales, i.e. from $\sim 10^2$ km to $\sim 300$ m. We show that for $k_{\perp}\rho_e \in[0.03,3]$ (that corresponds approximately to the frequency in the spacecraft frame $f\in [3,300]$ Hz), all the observed spectra can be described by a general law $E(k_\perp)\propto k_\perp^{-8/3}\exp{(-k_\perp \rho_e)}$, where $k_{\perp}$ is the wave-vector component normal to the background magnetic field and $\rho_e$ the electron Larmor radius. This exponential tail found in the solar wind seems compatible with the Landau damping of magnetic fluctuations onto electrons.Comment: published in APJ, 15 of November 2012 (with reduced "Discussion" section

Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Goniopolarimetric Properties and Radio Source Locations

We have performed statistical analysis of a large number of Type III radio bursts observed by STEREO between May 2007 and February 2013. Only intense, simple, and isolated cases have been included in our data set. We have focused on the goniopolarimetric (GP, also referred to as direction-finding) properties at frequencies between $125$ kHz and $2$ MHz. The apparent source size $\gamma$ is very extended ($\approx60^\circ$) for the lowest analyzed frequencies. Observed apparent source sizes $\gamma$ expand linearly with a radial distance from the Sun at frequencies below $1$ MHz. We have shown that Type III radio bursts statistically propagate in the ecliptic plane. Calculated positions of radio sources suggest that scattering of the primary beam pattern plays an important role in the propagation of Type III radio bursts in the IP medium

The Potential of Nuclear SMR in the Norwegian Energy Mix : Economic and financial analysis of SMRs in Norway

The primary purpose of this thesis is to determine the feasibility of incorporating small modular reactors (SMR) into the Norwegian energy mix, considering Norway's role in a larger integrated power market with direct grid connections to several European countries. Three analyzes were conducted to evaluate this: Initially, we conducted a literature review to determine if there is room for nuclear energy in the Norwegian energy mix and to compare nuclear energy with other relevant sources on a variety of financial and socioeconomic metrics to determine its potential value relative to relevant alternatives. Finally, we conducted a profitability analysis to determine the potential value creation of an SMR project. This approach aims to provide a nuanced perspective on the potential of allowing nuclear energy production in Norway. The primary findings suggest that SMR technology has significant potential in the Norwegian energy mix. With the green transition, the market analysis predicts a substantial increase in energy demand through 2050. In addition, the energy prices observed over the past few years are likely to decrease by 2030. With the current energy policies, however, there is a substantial risk of deviations between demand and supply, thereby severely jeopardizing the power balance and causing volatile power prices. Potentially resolvable by the addition of a stable and to a large extent dispatchable energy source, such as SMR. The comparative analysis demonstrates that nuclear energy has acquired an undeservedly negative reputation, despite appearing to be one of, if not the most environmentally friendly and secure energy source available today. In addition to being highly cost-competitive with sources such as offshore wind and solar, especially when the need for energy storage and external costs is considered. Our analysis of profitability is based on several assumptions. Seeing as SMR is a new and untested technology, its validity is difficult to assess. Nevertheless, based on these assumptions, our findings indicate that SMR projects would require reasonable financing in order to create shareholder value due to their substantial initial investment. With the long and stable cash flow, however, our base case estimates indicate that a project could achieve a payback period of approximately 20 years, with an accumulated positive net cash flow of between 60 and 70 billion NOK. Which, with discounting effects included, results in a net present enterprise value of 2-3 billion NOK. In addition, a levelized cost of electricity of around 65 øre/Kwh is achieved, which is particularly competitive compared to offshore wind.nhhma

Thermal radiation antennas made of multilayer structures containing negative index metamaterials

We investigate the thermal antenna behavior of emissive/absorptive substrates coated by passive optical multilayer systems that contain negative refractive index metamaterials (NIM). Spectral and angular distributions of the thermal radiation emittance for periodic defect-containing multilayer with NIM is addressed. We analyze realistic finite structures and took into account dispersion and losses in the NIM part. The application of NIM-containing 1D structures offers new degrees of freedom for the design, thus opening a path to obtain spectrally and spatially selective thermal emitters that could lead to improvements in the existing systems for thermal radiation control

Coupled optical defect cavities in finite 1-D photonic crystals and quasi-normal modes

We analyze coupled optical defect cavities realized in finite one-dimensional photonic crystals (PC). Viewing these as open systems, where waves are permitted to leave the structures, one obtains eigenvalue problems for complex frequencies (eigenvalues) and quasi-normal modes (QNM) (eigenfunctions). Single-defect structures (PC atoms) can be viewed as elementary building blocks for multiple-defect structures (PC molecules) with more complex functionality. The QNM description links the resonant behavior of individual PC atoms to the properties of the PC molecules via eigenfrequency splitting. A variational principle for QNMs permits one to predict the eigenfield and the complex eigenvalues in PC molecules, starting with a field template incorporating the relevant QNMs of the PC atoms. Furthermore both the field representation and the resonant spectral transmission close to these resonances are obtained from a variational formulation of the transmittance problem using a template with the most relevant QNMs. The method applies to both symmetric and nonsymmetric single and multiple-cavity structures with weak or strong coupling between the defects

A zone of preferential ion heating extends tens of solar radii from Sun

The extreme temperatures and non-thermal nature of the solar corona and solar wind arise from an unidentified physical mechanism that preferentially heats certain ion species relative to others. Spectroscopic indicators of unequal temperatures commence within a fraction of a solar radius above the surface of the Sun, but the outer reach of this mechanism has yet to be determined. Here we present an empirical procedure for combining interplanetary solar wind measurements and a modeled energy equation including Coulomb relaxation to solve for the typical outer boundary of this zone of preferential heating. Applied to two decades of observations by the Wind spacecraft, our results are consistent with preferential heating being active in a zone extending from the transition region in the lower corona to an outer boundary 20-40 solar radii from the Sun, producing a steady state super-mass-proportional $\alpha$-to-proton temperature ratio of $5.2-5.3$. Preferential ion heating continues far beyond the transition region and is important for the evolution of both the outer corona and the solar wind. The outer boundary of this zone is well below the orbits of spacecraft at 1 AU and even closer missions such as Helios and MESSENGER, meaning it is likely that no existing mission has directly observed intense preferential heating, just residual signatures. We predict that {Parker Solar Probe} will be the first spacecraft with a perihelia sufficiently close to the Sun to pass through the outer boundary, enter the zone of preferential heating, and directly observe the physical mechanism in action.Comment: 11 pages, 7 figures, accepted for publication in the Astrophysical Journal on 1 August 201

Strategy for Sustainable Development and Utilization of Sheep and Goat Resources in Serbia

The aims of this study were to determine the status of small ruminant production in Serbia and to provide projections for their sustainable use with optimal strategy of genetic improvement of sheep and goats in the future. For sustainable sheep and goat production, it is necessary to know a number of biological, technological, organizational and market factors. Number of sheep in Serbia during the past two decades fell by about 20%.  This  country grows more than 1.7 million sheep. In terms of breed structures, most of the populations are indigenous Pramenka sheep (80%), while the remaining 20% are Tsigai, Merinolandschaf, Ile de France, Pirot improved, Mis sheep, and other less important populations, as well as the crossbreed with foreign and domestic sheep. Interest of goat rearing is constantly increasing in last years for 20-30%.  In regard to the breed structure, the least represented are goats of Alpine breed – approx. 2- 3%, White Serbian goat - 15%, different types of crosses – approx. 35% same as goats of low land Balkan type, and approx. 12% of high land Balkan type. Strategy of sheep and goat breeding programs in Serbia is focused on the improvement of indigenous breeds, because they are less demanding, and most importantly, the input is lower and their products have higher quality. Keywords: sheep; goat; sustainable; resources; meat; mil