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Transient electromagnetic wave propagation in a stratified, anisotropic, dispersive medium is considered. Specifically, the direct scattering problem is addressed. The dispersive, anisotropic medium is modeled by constitutive relations (a 3 3 matrix-valued susceptibility operator) containing time convolution integrals. In the general case, nine different susceptibility kernels characterize the med
The sea elevation at a fixed point is modelled as a quadratic form of a vector valued Gaussian process with arbitrary mean. With this model, saddlepoint methods are used to approximate the mean upcrossing intensity with which the sea level crosses upwards at a certain height. This estimated intensity is further used to determine the probability distribution of wave crests. The use of saddlepoint t
In this paper, wave propagation of electromagnetic pulses in media that are periodic in one spatial direction is analyzed by a time domain technique. The special case of wave propagation in an inhomogeneous planar waveguide with perfectly conducting walls is also discussed. The wave equation is reduced to a set of one dimensional first order hyperbolic equations by an expansion in a complete set o
Cool flame has an important impact on the performance and emission of advanced low-temperature combustion (LTC) internal combustion engines (ICEs) in which the liquid fuel is injected earlier at a lower ambient temperature (Tam) than that in the conventional diesel combustion engines. However, the cool flame characteristics of spray combustion under ICEs conditions are not fully understood, e.g.,
In this paper transient electromagnetic wave propagation in a stratified, anisotropic, dispersive medium is considered. Specifically, the direct scattering problem is addressed. The dispersive, anisotropic medium is modeled by constitutive relations (a 3 × 3 matrix-valued susceptibility operator)con taining time convolution integrals. In the general case, nine different susceptibility kernels char
One-dimensional propagation of transient EM-waves in periodic media is studied. The media are periodic in the direction of propagation and can be of finite or infinite length. Wave propagators, that map a transient field from one point in the medium to another, are introduced. A number of useful relations for the propagators are presented. Some of these relations are used in the determination of e
Wave propagators are introduced for transient wave propagation in a general one-dimensional medium. The definition of wave propagators is based upon a wave splitting technique. Several properties for the propagators are given and the relations between the method of propagators and the invariant imbedding method and the Green function approach are discussed.
This thesis aims to characterize and counteract the wave steepening effect in a horn loaded loudspeaker. The report consists of two main parts. The first part, the characterization of the horn speaker system, focuses on investigating and understanding the signal distortions introduced by the speaker system. In particular, non-linear distortion is examined to determine any parameter dependence of t
Part of the Sound Studies Lecture Series NIKOLAOS GEORGIOS VARDAXIS Acoustics refers to the science of sound, its properties and propagation, while the same term is often used to refer to sound qualities of an environment, an indoor space or somewhere outdoors. This lecture offers an introduction to basic acoustic concepts such as sound pressure levels, which is the most essential quantity when de
https://www.lmc.lu.se/aktiviteter/aktiviteter-2020/introduction-acoustic-concepts-relevant-sound-studies - 2026-07-17
The role of hybridization in evolution has been debated for more than a century regarding bryophytes (mosses, liverworts, and hornworts) as well as most other organisms. Bryophytes have haplodiplontic life cycles with a dominant haploid generation. Hybridization in bryophytes involves fusion of gametes produced by haploid parental gametophytes of different species. The hybrid is thus the short-liv
Through the advent of high-order harmonic generation and attosecond light pulses, photoionization dynamics has been studied on the attosecond time-scale, the intrinsic time-scale of such dynamics. When the electron leaves the atomic potential a phase shift is imprinted on the electron wavefunction. The measurement of this phase, together with amplitude allows us to determine the dynamics that of t
We use crystal-phase tuning during epitaxial growth of InAs nanowires to create quantum dots with very strong confinement. A set of gate electrodes are used to reproducibly split the quantum dots into even smaller pairs for which we can control the populations down to the last electron. The double quantum dots, which are parallel-coupled to source and drain, show clear and stable odd-even level pa
This thesis investigates electronic transport in several types of novel heterostructure nanowires. The first part of the thesis focuses on band-to-band mechanisms in heterostructure nanowires for low-power electronics. First, tunnel field-effect transistors (TFETs) based on InP/GaAs heterostructure nanowires with n-i-p doping profile are explored. To further enhance the interband tunneling current
The ability to manipulate spin states with light forms the basis of spin-based photonics. The development of semiconductors with tunable spin properties will enable devices that use spin for information storage, circular polarized light emission, etc. With the recent reports of a chirality-induced spin selectivity (CISS) effect in electrons, the question arises whether structural chirality provide
