<p>In this master thesis, full-waveform inversion (FWI) was applied to a synthetic, and very complex, geological structure containing a salt body. The main objective was to evaluate the capabilities of FWI to estimate velocities in this context, and more specially below the salt. Seismic depth imaging is now the preferred seismic imaging tool for today's most challenging exploration projects. Seismic depth imaging problem usually requires the definition of a smooth background velocity model before determining the short wavelength component of the structure by pre-stack depth migration. It is well established that success of pre-stack depth migration in complex geological media strongly depends from the definition of the background velocity model. Standard tools for building velocity models generally fail to reconstruct the correct sub-salt velocities. Sub-salt imaging is a very challenging problem and a lot of resources are spent trying to solve this problem, since salt bodies in the sub-surface are known to be very good hydrocarbon traps. In this master thesis, the work have been performed on a modified version of the 2004 BP velocity benchmark model. This model represents a very interesting salt context, where conventional imaging methods can not provide any good results. After describing the seismic inversion problem, and the FWI theory and code used in this work, the application to the 2004 BP benchmark model is described. FWI was first applied to the synthetic data using a starting model derived by smoothing the true velocity model. This is an easy way to ensure an adequate starting model, as the method is very dependent on a good starting model. In the inversion process 17 frequency components were used, ranging between 1 and 15 Hz. This resulted in a velocity model that accurately recovered both the salt body and the sub-salt velocities. The average deviation between the true and estimated sub-salt velocities was found to be approximately 6 %. A more realistic starting model was then derived using first-arrival traveltime tomography, a well known method for obtaining velocity models. FWI was applied to this starting model, and the result was also positive when using this starting model. The salt body was well delineated, whereas the sub-salt velocities were generally more inaccurate than for the previous application. The sub-salt velocity difference was increased to roughly 10 %. However, if more effort had been spent on reconstructing a more accurate starting model, the results might have improved. When fewer frequency components are used in the inversion, the result declined. A test using only 6 frequency components showed that the final reconstructed model suffered from a lack of recovered wavenumbers, especially at the deeper and more complex parts of the model. In such a complex medium as the 2004 BP benchmark model, it is hence necessary to introduce wavenumbers by including a sufficient number of frequency components in the inversion process. Other tests that were conducted showed that, in this particular case, the non-linearity of the inversion problem increased with higher frequencies, and was reduced by larger offset ranges included in the seismic data. The inversion is hence sensitive to the starting frequency as well as the starting model. The results in this master thesis demonstrate that FWI has a great potential in reconstructing sub-salt velocities in salt media. For the future, both applying the method to real data from a salt basin area, and develop a migration tool and test the effect of FWI on a migrated image, are interesting challenges.</p>

<p>Over the last few years the ship traffic in polar areas have been steadily increasing, especially north of Norway. This is largely due to the growing activity in that area and in northern Russia, mainly from oil and gas exploration and production. All indications suggest that this will continue into the foreseeable future. In this report a satellite based system for broadband communications to the area north of 65 northern latitude is discussed. Possible carrier frequency configurations and their propagation properties is analysed, and it is found that Ka-band, 20/30GHz, will give best performance. Various satellite orbits are then discussed, and a constellation that give continueous coverage and allow for easy handover is designed. It consists of four satellites in Molniya orbits with an eccentricity of approximately 0.72. Each satellite is then operational and quasi-stationary for six hours of every orbit, with two satellites above the coverage area at any time. Solutions for the satellite antennas are considered, and link budgets are presented. Active phased arrays are found to provide the best performance. A total uplink capacity of 1.6 Gbps is teoretically possible with a user terminal output power of 100W, but it is not deemed realizable. Instead a configuration with a total capacity on both uplink and downlink of about 1 Gbps is suggested. At the end of the report a range of issues, related to the realization of the satellite system, requiring future attention is summarized and briefly discussed.</p>

<p>PlaneRay, an acoustic underwater propagation model based on ray tracing and plane- wave reection coecients, has been used to model wave propagation in shallow water environments. The program has emulated a seismic vessel towing a source-receiver setup and represented the shape of the sea oor as time responses plotted for a xed source- receiver distance over an increasing source range. The eects of the water's sound speed prole and the sea oor's topography have been studied in detail, and the program's robustness and capability to handle these problems have been discussed and found sat- isfying.</p>

<p>Optical spectroscopy has been well validated by the physical sciences as a method to characterize chemical compositions in biological material. It has also showed promising to detect atherosclerotic plaques, which can form in the coronary artery walls, and cause heart attacks and strokes. This project seeks to optimize and build fiber optic probes for diffuse reflectance and fluorescence spectroscopy which can assess these plaques. A side-viewing probe is particularly advantageous in the small diameter, confined geometries of arteries. Thus, different techniques are investigated for creating lenses on the tip of optical fibers and design the probes so that they can perform spectroscopic measurements along its circumference. A rigorous testing scheme was developed which included a test matrix and a set of criteria that were used in the optimization process. Two probes for diffuse reflectance and one for fluorescence measurements were built based on the result from the testing scheme. However, a combined probe optimized for both diffuse reflectance and fluorescence measurements could not be created as their respective optimization criteria turned out to be contradictory. The final reflectance probes consisted of two 200 micron fibers separated by 2 mm in the axial direction and the fiber tips were shaped by using a CO2 laser and grinding machine. All the finished probes were tested in a coronary artery of a porcine heart and fat was injected to evaluate their detection of lipid pools. The probes showed good results and were able to detect changes in chromophore content in the tissue and demonstrated the advantages of optimizing a probe for its given application. The fluorescence probe turned out to give good results when used on the arteries from the surface of the heart surface.</p>

<p>In this master thesis a software, MapMonit, that use real measurement data as a basis to calculate noise maps was studied. The project focus on noise from roads. Simulations in MapMonit based on measurements were compared with control measurements and simulations of existing noise computation software. The software used for comparison was CadnaA. The project started with measurements of road traffic noise with four microphone heights at four distances that would be used as input to the software called MapMonit. Since this was the first time the software ever got tested with real measurements, the first test site was chosen to be as simple as possible with a long, straight road and surrounding flat fields. The microphone distances from the road edge were 5 m, 10 m, 20 m and 100 m with microphone heights 0.4 m, 1.5 m, 2 m and 4 m at each of the distances. A grid of control microphones were positioned in the vicinity from 10 m to 180 m from the road edge. At distances 5 m to 20 m for microphone heights 1.5 m to 4 m, the results turned out to be very good. The difference between the A-weighted levels of MapMonit simulations and the control measurements was generally less than 1 dB for all control positions. Compared to CadnaA, the two simulated levels were very similar for propagation paths up to 100 m with differences below 1.4 dB. At control distances over 170 m, the difference was very high, up to 5.3 dB, with MapMonit simulating the highest values. A complicated test site in the vicinity of a noise screen were also studied. The reference microphones for input to MapMonit were placed in front, above and behind the screen, and one behind a garage also on the quiet side. The control measurements were placed around the neighborhood at the quiet side of the noise screen. Due to a flaw with the MapMonit software implementation, the results were presented with flat topography. The reference microphone in front of and above the noise screen gave satisfying results, with differences less than 2 dB at all control positions except for a position just behind a garage. Obstacles along the propagation path included both a noise screen and buildings. Choosing the microphone mounted just above the noise screen, the difference between the A-weighted levels of CadnaA and MapMonit was less than 1 dB for all positions except the one behind the garage.</p>

<p>In this report a phenomenological characterization technique of received bottom echoes has been developed and studied, to evaluate the potential of locating typical sandeel grounds. Data from a calibrated multi--frequency echosounder collected during a Survey Methods for Abundance Estimation of Sandeel (Ammodytes marinus) Stocks (SMASSC) survey in the sandeel fishing grounds of "Vestbanken" and "Elbow Spit North", were processed with developed scripts in Matlab to extract first received bottom echo parameters. Together with Simrad SEABEC results and sandeel samples, possible distinctive parameters were found for what could be sandeel grounds. However, ambiguities caused by ping to ping fluctuations and complex behavior of the sandeel species make the characterization difficult. Many of the calculated echo parameters showed possible discrimination power for a future multi-variate analysis.</p>

<p>Wireless data networks have seen rapid growth and deployment in the recent years, replacing traditional wired data networks. WesternGeco is currently using a traditional wired data network in the land seismic operations to connect the Head Vibrator with the Recording Truck. The thesis provides a survey of the most important wireless data network technologies available. A comparison between them is done in order to determine the best suited for WesternGeco’s communication mechanism. The study has lead to the conclusion that IEEE 802.11g is the most suited technology. Through the use of high gain antennas, modification of MAC layer parameters and the proper channel allocation, the suggested solution is capable of responding what WesternGeco needs.</p>

<p>The final goal of this document is the construction of multi-band terminal for the CVIS project to allow the communication among cars and between the cars and the roadside infrastructure. For the construction of this multi-band terminal, this document takes as starting point, a new compact disk antenna described in [1]. It consists in a circular patch antenna shorted by a central metallic post. This allows reducing the dimensions of a classical circular patch antenna so it is very useful for our application given that the terminal is going to be place on the top of a car and it should be small enough to be attractive for the final users. Specifically, we are going to analyze the behaviour of this kind of antenna when it radiates in the TM01 mode, because the radiation pattern of this mode is particularly interesting for the applications of the CVIS project. This document is divided into two main parts. In the first one, a study in depth of the behaviour of the antenna proposed in [1] was performed. Firstly, through an analytical model and afterward with the help of two simulation tools (WIPL-D and EMDS), we analyze the influence of the main parameters of the antenna (outer and inner radiuses, height, electrical permittivity and the position of the feed) on its properties (resonant frequency, bandwidth, entrance impedance, the shape of the radiation pattern and so on). A general methodology for the design of this kind of antennas was proposed, and it was put in practice with the design of a prototype for a band around 2 GHz. In addition to the conclusions about the influence of the different parameters of the antenna, another important conclusion was done. It was discovered that the use of the simulation tool WIPL-D Lite was not suitable for the simulation of this kind of antenna. In the second part, this document tackles the construction of a dual-frequency antenna for the bands of 2.4-2.484 GHz and 5.75-5.95 GHz. For this, the present document studies the possibility of stacking two compact circular patch antennas, so we put the one which covers the higher band (the smaller) on the top of the one which covers the lower band (the lager). The two patch antennas have a coaxial feed and the feed of the upper antenna goes inside the central post of the lower antenna to minimize the influence of it on the radiation pattern of the lower antenna. This proposal works out not to be feasible, because we need a lower antenna with a large inner radius to allow the variation of the feed position of the upper antenna in a wide range. This is necessary to get a good matching for the upper antenna. The problem is that the radiation pattern becomes very asymmetric when we increase the inner radius of the patch antenna. To solve that, two alternative were analyzed in this document. The first consists in putting a second feed symmetrically placed with respect to the central post. It leads to a more symmetric radiation pattern so we can choose a larger inner radius. In addition, the introduction of the second feed increases the bandwidth of the antenna. The second alternative is a simplification of the first one. It consists in replacing the upper antenna with a monopole on the top of the lower antenna. It is simpler but it prevents the possibility of stacking other patch antennas to cover more frequency bands in a future. Due to this disadvantage, the first alternative was chosen. Finally, a proposal based on the first alternative, which fulfils quite well all the requirements which were raised in the wording of this master thesis, was presented and studied in depth.</p>

<p>The rules of quantum mechanics makes it possible to exchange a secret key at a distance. This is called quantum key distribution (QKD). In theory the key exchange can be made completely secure. Real QKD implementations however, has numerous imperfections. Luckily one has also been able to prove the security of QKD with a large variety of imperfections. The field of QKD has matured over the recent years, and it has now reached commercial applications with photons as the quantum bits, and optical fibers as the quantum channel. Today there are at least three commercial vendors of QKD-systems. We live in the times of quantum hacking. Researchers has begun the task of breaking the security of QKD-systems. Many new imperfections has been discovered, some of which might be used to break the security of QKD. This thesis is a study of the detector efficiency mismatch loophole. Most QKD-systems require two detectors, and it is virtually impossible to make two identical detectors with the exact same efficiency. What is worse, it turns out that the eavesdropper can often control the relative efficiencies of the two detectors trough some domain, for instance by controlling the timing, the frequency or the spacial mode of the photons. This can in turn be used by the eavesdropper to gain information about the secret key. Previously the best known attack would compromise security if the detector efficiency mismatch of about 1:15. Here the current attacks on systems with detector efficiency mismatch are improved to compromise security for a mismatch of about 1:4. This is less than the mismatch found in a commercial QKD-system, so the attack could in principle be used to eavesdrop on this QKD-system. One might try to close the loophole by modifying the implementation. One suggestion is the four state Bob. The problem is that this patch will in turn open other loopholes, and one of these loopholes reopen the detector efficiency mismatch loophole. One can remove Eves information about the key by doing a sufficient amount of extra privacy amplification. Here a general security bound is presented, quantifying the required amount of extra privacy amplification to remove Eve's information about the key. The proof is more general than the previous security proof, and is valid for any basis dependent, possibly lossy, linear optical imperfections in the channel and receiver/detectors. Since this is more realistic assumptions for a QKD-implementation, the proof represents a major step of closing the loophole in real devices.</p>

<p>In the last two decades, magnetic resonance spectroscopy (MRS) has had an increasing success in biomedical research. This technique has the faculty of discerning several metabolites in human tissue non-invasively and thus offers a multitude of medical applications. In clinical routine, quantification plays a key role in the evaluation of the different chemical elements. The quantification of metabolites characterizing specific pathologies helps physicians establish the patient's diagnosis. Estimating quantities of metabolites remains a major challenge in MRS. This thesis presents the implementation of a promising quantification algorithm called selective-frequency singular value decomposition (SELF-SVD). Numerous tests on simulated MRS data have been carried out to bring an insight on the complex dependencies between the various components of the data. Based on the test results, suggestions have been made on how best to set the SELF-SVD parameters depending on the nature of the data. The algorithm has also been tested for the first time with in-vivo 1H MRS data, in which SELF-SVD quantification results allow the localization of a brain tumor.</p>