The thesis deal with possibility of localization of avalanche victims. Main focus is for RF avalanche beacons. The major objects of this thesis are design and construction of this device. A large part of thesis describes design of avalanche beacon and particular steps of realization. The design take into account the compatibility with commercial beacons. The paramters of designed device are verified by testing and measurement.

The aim of this diploma work is accuracy assesment of underground spaces electromagnetic localization method and comparison with results made by Ing. Matin Šklíba in 2006. Existing Purpose-built geodetic control Býčí skála and previous measuring for past 15 years was used for accuracy assessment.

This dissertation thesis deals with a long range free space optical links for communication over the distance of few tens of kilometers in the atmosphere. The problematic of the beam propagation and atmospheric effects influencing the beam and the quality of the communication protocol are discussed. The measuring link is also designed to study the parameters of the communication link work conditions. The measuring link consists of two heads. The transmitter head is designed to use two optical beams with laser diodes at the wavelength of the atmospheric windows 850 or 1550 nm and the overall power of hundredths of mW. The receiver head includes the Fressnel lens. For the detection of very weak signal, the avalanche photodiode is used. In the end of this work, due to the high power of the transmitting optical beam, the laser safety conditions are also discussed, including the deduced optical transmitters construction recommendations.

This work is focused on free space optical communication in visible electromagnetic spectrum known as visible light communication (VLC). Basic parameters of standard IEEE 802.15.7, advantages and disadvantages are discussed in the theoretical part of this work. Furthermore, optical link and it´s parts are described. The largest part of the work is focused on design and simulation of optical receiver for visible spectrum. Selection of component, noise and SNR calculation is discussed as well. This work also includes calculation of power energy in different parts of optical connection, PCB design of optical receiver, transmitters and power supply and output board. Behavior and parameters of electronic circuits, components and optical connection are explored, measured and compared with theoretical values.

La géologie, et plus particulièrement la géophysique, repose sur l’observation, directe et indirecte, de phénomènes se produisant en surface et dans les profondeurs de la Terre. Ces observations nous permettent d’étudier et définir la structure et les dynamiques globales de la Terre. L’étude des ondes sismiques générées par les tremblements de terre les plus puissants permet, par exemple, d’entrevoir la structure des hétérogénéités dans les premières centaines de kilomètres de la Terre. Dans cette thèse, nous nous intéressons au champ d’onde diffracté, qui est composé des arrivées tardives qui suivent les ondes incidentes. Par définition, les ondes diffractés contiennent de l’information liée aux hétérogénéités diffractantes, autrement dit les structures à petite échelle de la Terre, qu’elles rencontrent le long de leur trajet. De ce fait, il est possible d’étudier les variations rapides de vitesses sismiques grâce au champ d’onde diffracté, alors que ces informations seraient perdues dans les méthodes tomographiques à cause des facteurs de régularisation. Afin d’exploiter le champ d’onde diffracté, on a recours aux fonctions récepteurs (« receiver function » en anglais, RF) et à la migration sismique en profondeur de pré-empilage. Les procédures standard de migration sismiques sont de deux types principaux. Le premier type de procédures, dont l’exemple type est la migration en point de conversion communs (« common conversion point » en anglais, CCP) est rapide mais repose sur l’hypothèse fondamentale que les discontinuités que l’on cherche à imager sont horizontales. Le second type de procédures, pour lesquelles on peut citer la « reverse time migration » (RTM), ou la « generalized radon transform » (GRT), ne font pas d’hypothèse sur la structure du sous-sol, mais demandent une forte intensité des calculs et sont de fait souvent limités à des géométries bidimensionnelles. Au cours de ce manuscrit, nous développons une migration sismique de type Kirchhoff qui se base sur des calculs de temps de trajet sismique rapides en trois dimensions et quasiment aucune hypothèse sur la structure du milieu sous-jacent. Cet algorithme efficace nous permet de nous affranchir des traditionnelles limitations à des études 1D ou 2D. Notre principe d’imagerie prend en compte les ondes diffractées transmises et réfléchies, et se place dans la suite des travaux de Cheng et al. (2016). Nous adaptons la migration de type Kirchhoff élastique aux géométries de diffraction inhérentes à la sismologie passive et prenons en compte les multiples de surface. Les temps de trajet de toutes les ondes diffractées sont calculées grâce à la « fast marching method » (FMM). Les amplitudes et la polarité des signaux des RF sont corrigées à l’aide du calcul de figures de diffraction 3D. Pour extraire l’information des conversions transmises et réfléchies de façon cohérente, les résultats pour chaque mode de diffraction sont sommés de plusieurs façons (linéaire, à filtre de phase, et à filtre d’amplitude non linéaire). Afin de démontrer l’efficacité et la précision de notre méthode de migration, nous procédons à des tests synthétiques, aussi bien dans des situations réalistes qu’artificiellement compliquées, en nous servant du logiciel Raysum. Les résultats de ces tests prouvent que cette méthode de migration permet d’obtenir une image fidèle du milieu imagé quasiment sans artéfacts. En intégrant les trois composantes des RF dans la migration, cette méthode de migration est capable d’exploiter l’information d’ondes arrivant avec n’importe quel angle d’incidence et n’importe quel azimut. Finalement, cette méthode de migration multi-mode 3D est appliquée à deux jeux de données de terrain issus de réseaux sismiques déployés au dessus de zones de subduction, en Grèce et en Alaska / In geology, and in particular in geophysics, direct and indirect observations of processes occurring both at the surface of the Earth and at depth are used to understand the structure and dynamics of the Earth. For instance, seismic waves generated by large earthquakes can be used to study the structure of heterogeneities in the first few hundred kilometers inside the Earth. In this work, we use the scattered wavefield, which corresponds to energy arriving after the incident wavefield, to image the Earth. By nature, the scattered waves are linked to the scattering heterogeneities encountered along their propagation path, i.e. the fine scale structure of the Earth. Hence, the scattered wavefield has the ability to highlight structures where rapid velocity variations would otherwise be smoothed out by tomographic regularization, such as the structure of subducting slabs. To extract the information from the scattered wavefield, we resort to receiver function (RF) analysis and pre-stack depth migration. Standard migration procedures either rely on the assumption that underlying discontinuities are horizontal, such as in Common Conversion Point stacking (CCP), or are computationally expensive and usually limited to 2D geometries, such as in Reverse Time Migration (RTM) or Generalized Radon Transform (GRT). Here, we develop a Kirchhoff-type teleseismic imaging method that uses fast 3D travel-time calculations with minimal assumptions about the underlying structure. This provides high computational efficiency without limiting the problem to 1D or 2D geometries. In our method, we apply elastic Kirchhoff migration to transmitted and reflected teleseismic waves (i.e., RF). The approach expands on the work of Cheng et al. (2016). The 3D elastic Kirchhoff migration is adapted to the passive seismology scattering geometry and to account for free surface multiples. We use an Eikonal solver based on the fast marching method (FMM) to compute travel times for all scattered phases. 3D scattering patterns are computed to correct the amplitudes and polarities of the three component input signals. We consider three different stacking methods (linear, phase weighted and 2 nd root) to enhance the structures that are most coherent across scattering modes. To showcase the efficiency and accuracy of our migration procedure, we test it by conducting a series of synthetic tests in both artificially challenging and realistic scenarios. Results from synthetic tests show that our imaging principle can recover scattering structures accurately with minimal artifacts. We show that integrating the three components of the RF into the imaging principle allows to coherently retrieve the scattering potential for arbitrarily dipping discontinuities from all back-azimuths, and are able to retrieve a typical 2.5D subduction zone structure. We apply this novel 3D multi-mode Kirchhoff migration method to two different subduction zones, in Western Greece and Southern Alaska

This study focused on a numerical second law analysis and optimisation of a receiver tube op- erating in a parabolic trough solar collector for small-scale application. The receiver functioned in a Rankine cycle. The focus was on entropy generation minimisation in the receiver due to the high quality exergy losses in this component. Water functioned as the working uid and was heated from ambient conditions (liquid) to a superheated state (vapour), consequently, the receiver tube was subject to both single phase as well as two-phase ow. Entropy generation in the receiver tube was mainly due to nite temperature di erences as well as uid friction. The contribution of each of these components was investigated. Geometrical as well as operating conditions were investigated to obtain good guidelines for receiver tube and plant design. An operating pressure in the range of 1 MPa (Tsat = 180 C) to 10 MPa (Tsat = 311 C) was considered. Furthermore a mass ow range of 0:15 kg=s to 0:4 kg=s was investigated. Results showed that beyond a diameter of 20 mm, the main contributor to the entropy generation was the nite temperature di erences for most conditions. Generally, operating pressures below 3 MPa showed bad performance since the uid friction component was too large for small operating pressures. This phenomenon was due to long two-phase lengths and high pressure drops in this region. The nite temperature di erence component increased linearly when the tube diameter was increased (due to the increase in exposed area) if the focused heat ux was kept constant. However, the uid friction component increased quadratically when the diameter was reduced. In general when the concentration ratio was increased, the entropy generation was decreased. This was due to more focused heat on each section of the receiver pipe and, in general, resulted in shorter receiver lengths. Unfortunately, there is a limit to the highest concentration ratio that can be achieved and in this study, it was assumed to be 45 for two-dimensional trough technology. A Simulated Annealing (SA) optimisation algorithm was implemented to obtain certain optimum parameters. The optimisation showed that increasing the diameter could result in a decrease in entropy generation, provided that the concentration ratio is kept constant. However, beyond a certain point gains in minimising the entropy generation became negligible. Optimal operating pressure would generally increase if the mass ow rate was increased. Finally, it was seen that the highest operating pressure under consideration (10 MPa) showed the best performance when considering the minimisation of entropy in conjunction with the maximisation of the thermodynamic work output. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Mechanical and Aeronautical Engineering / MEng / Unrestricted

Nowadays, mobile phones have greater functionality; a camera, color LCD screen, wireless LAN, Bluetooth, IrDA and others. In the near future wider variety of new functionalities will be added, from high quality voice, high definition video to high data rate wireless channels. As consumer electronics integrate greater functionality and high operating frequencies, their emissions will exceed the specified limits, most of these emissions will be a result of the internal interferences in the mobile phone. Moreover higher operating frequencies will be required to improve the quality of these functionalities, something that will make it more difficult to control these interferences. Internal or external sources of electromagnetic interference can degrade the performance of sensitive analog/digital circuits inside the mobile phone. Moreover the electronic device must satisfy a host of global regulations that limit it’s susceptibility to these interferences, as well as the interference emitted by the device itself. Therefore designing a new electronic device to perform new and exciting functions will not be a pleasant task if it can not meet certain specifications and function as required to adhere to certain global regulations. This thesis project investigates the sources of interference inside a mobile phone; mainly the electromagnetic interferences and its effect on the radio transceiver focusing on the GSM receiver sensitivity. This report is a result of intensive research, an investigation of possible sources of interference, also actual measurements were performed; RSSI, OTA and sniffing measurements; to identify the physical sources of interferences, and their effect on the receiver sensitivity. Finally solutions were recommended and implemented to suppress the interferences due to different sources, mainly through filtering, shielding or proper grounding of signals and components/subsystems in the mobile phone.

Concentrated Solar Power (CSP) constitutes one suitable solution for exploiting solar resources for power generation. In this context, parabolic dish systems concentrate the solar radiation onto a point focusing receiver for small-scale power production. Given the modularity feature of such system, the scale-up is a feasible option; however, they offer a suitable solution for small scale off-grid electrification of rural areas. These systems are usually used with Stirling engines, nevertheless the coupling with micro-gas turbines presents a number of advantages, related to the reliability of the system and the lower level of maintenance required. The OMSoP project, funded by the European Union, aims at the demonstration of a parabolic dish coupled with an air-driven Brayton cycle. By looking at the integrated system, a key-role is played by the solar receiver, whose function is the absorption of the concentrated solar radiation and its transfer to the heat transfer fluid. Volumetric solar receivers constitute a novel and promising solution for such applications; the use of a porous matrix for the solar radiation absorption allows reaching higher temperature within a compact volume, while reducing the heat transfer losses between the fluid and the absorption medium. The aim of the present work is to deliver a set of optimal design specifications for a volumetric solar receiver for the OMSoP project. The work is based on a Multi-Objective Optimization algorithm, with the objective of the enhancement of the receiver thermal efficiency and of the reduction of the pressure drop. The optimization routine is coupled with a detailed analysis of the component, based on a Computational Fluid Dynamics model and a Mechanical Stress Analysis. The boundary conditions are given by the OMSoP project, in terms of dish specifications and power cycle, whilst the solar radiation boundary is modelled by means of a Ray Tracing routine. The outcome of the analysis is the assessment of the impact on the receiver performance of some key design parameters, namely the porous material properties and the receiver geometrical dimensions. From the results, it is observed a general low pressure drop related to the nominal air mass flow, with several points respecting the materials limitations. One design point is chosen among the optimal points, which respects the OMSoP project requirements for the design objectives, i.e. a minimum value of efficiency of 70%, and pressure losses below 1%. The final receiver configuration performs with an efficiency value of 86%, with relative pressure drop of 0.5%, and it is based on a ceramic foam absorber made of silicon carbide, with porosity value of 0.94.  Moreover, the detailed analysis of one volumetric receiver configuration to be integrated in the OMSoP project shows promising results for experimental testing and for its actual integration in the system.

This work presents design and full implementation of a fast switchable and band-tunable 5 - 7.5 GHz low noise amplifier (LNA) in a 45nm CMOS SOI technology. The target application are wake-up receivers that employ aggressive duty cycling. Based on a cascode topology, the LNA utilizes a transformer for its 50 input matching as well as a balun with a capacitor bank to realize 8 digitally selectable bands. According to measurement results, the fabricated LNA exhibits a voltage gain of 18 - 21 dB while drawing a current of merely 2.2mA from a 1V supply. At all the 8 bands from 5 to 7.5 GHz, the input reflection coefficient lies below -8 dB, and the noise figure ranges from 7.8 to 6.2 dB. The LNA is able to settle in less than 9.5 ns

Philosophiae Doctor - PhD / Expressed sequence tag database is a rich and fast growing source of data for gene expression analysis and drug discovery. Clustering of raw EST data is a necessary step for further analysis and one of the most challenging problems of modem computational biology. There are a few systems, designed for this purpose and a few more are currently under development. These systems are reviewed in the "Literature and software review". Different strategies of supervised and unsupervised clustering are discussed, as well as sequence comparison techniques, such as based on alignment or oligonucleotide compositions. Analysis of potential bottlenecks and estimation of computation complexity of EST clustering is done in Chapter 2. This chapter also states the goals for the research and justifies the need for new algorithm that has to be fast, but still sensitive to relatively short (40 bp) regions of local similarity. A new sequence comparison algorithm is developed and described in Chapter 3. This algorithm has a linear computation complexity and sufficient sensitivity to detect short regions of local similarity between nucleotide sequences. The algorithm utilizes an asymmetric approach, when one of the compared sequences is presented in a form of oligonucleotide table, while the second sequence is in standard, linear form. A short window is moved along the linear sequence and all overlapping oligonucleotides of a constant length in the frame are compared for the oligonucleotide table. The result of comparison of two sequences is a single figure, which can be compared to a threshold. For each measure of sequence similarity a probability of false positive and false negative can be estimated. The algorithm was set up and implemented to recognize matching ESTs with overlapping regions of 40bp with 95% identity, which is better than resolution ability of contemporary EST clustering tools This algorithm was used as a sequence comparison engine for two EST clustering programs, described in Chapter 4. These programs implement two different strategies: stringent and loose clustering. Both are tested on small, but realistic benchmark data sets and show the results, similar to one of the best existing clustering programs, 02_cluster, but with a significant advantage in speed and sensitivity to small overlapping regions of ESTs. On three different CPUs the new algorithm run at least two times faster, leaving less singletons and producing bigger clusters. With parallel optimization this algorithm is capable of clustering millions of ESTs on relatively inexpensive computers. The loose clustering variant is a highly portable application, relying on third-party software for cluster assembly. It was built to the same specifications as 02_ cluster and can be immediately included into the STACKPack package for EST clustering. The stringent clustering program produces already assembled clusters and can apprehend alternatively processed variants during the clustering process.