I denne oppgaven har i hovedsak to teorier blitt undersøkt :1) er det mulig ved hjelp av ørepropper med høyttaler og mikrofon ådetektere snorking og deretter spille tilbake lyder som får personen tilå stoppe snorkingen, og2) er det mulig å klassisere ulike snorketyper ved hjelp av analysemetoderbrukt i talegjenkjenning.Først ble det utviklet og testet to forskjellige ørepropper som varbehagelige å sove med. Den ene av de to ble brukt videre i arbeidetmed å detektere og analysere snorkingen, og viste seg å fungere tilfredstillende.Videre ble det utviklet en snorkedetektor basert på spektrale ogtemporale egenskaper ved snorking. Den er følsom for andre lyder ennsnorking, slik at den gir mange feildeteksjoner. Bortsett fra dette, fangerden opp snorking slik man ønsket.Neste forsøk gikk ut på å undersøke om forsøkspersonen sluttetå snorke når det ble spilt tilbake lyd i øreproppen. Det viste seg atpersonen reagerte best i startfasen av søvnen, og veldig dårlig ved dypsøvn. Personen begynte som regel å snorke igjen allerede etter 10-20sekunder, slik at man kan slå fast at denne teorien ikke ga den ønskedeeffekten.Tilslutt ble det undersøkt om det var mulig å klassifisere snorking.Frekvensspekteret viste ingen framtredende særtrekk som gjorde detmulig å skille snorketyper. Derimot lot det seg gjøre å klassisere tosnorketyper ved å analysere reeksjonskoesientene fra LPC-analyse.I det materialet som ble testet, klarte algoritmen å klassisere snorketypenekorrekt for alle pasientene.Dette arbeidet viser at akustisk analyse av snorking kan ha noe forseg i medisinsk diagnostisering. Det viser seg også at å gi lydstimuleringtil en person som snorker ikke hadde den ønskede effekten.

Intermediate band solar cells (IBSC) is a proposed new type of solar cell device that has an intermediate energy band in the band gap. One possible implementation of IBSCs is by using arrays of nano-sized semiconductor particles known as quantum dots (QDs). InAs QDs can be grown on GaAs by using molecular beam epitaxy (MBE). As a part of this growth process, an InAs wetting layer (WL) is formed on which the InAs QDs grow. One possible method of determining the WL thickness is by using x-ray diffraction (XRD), which is a non-destructive analysis technique used to extract information about the structure and composition of crystalline thin films.An InAs/GaAs bilayer sample grown by MBE was investigated. This sample was grown without rotation, meaning the thicknesses of the deposited layers are expected to exhibit a gradient across the sample. Based on the geometry of the MBE machine, the variation in deposited thicknesses across the sample was estimated to be ±3.4% for InAs and ±4.2% for GaAs. XRD rocking curve measurements were performed around the 004 reflection in thirteen different locations on this sample. LEPTOS software was used to simulate XRD curves, and these simulations were fitted to the XRD measurements by varying the thicknesses of the simulated InAs and GaAs layers. It was found that the GaAs thicknesses across the sample varied as expected, while the variation in InAs thicknesses was much larger than expected. It was also found that the measured thicknesses of the InAs layer were significantly thinner than the nominal value. This is a strong indication that there are QDs on the sample, and that only the WL of the QDs contributes to the x-ray curve.LEPTOS was also used to simulate several cases of alloying of an InAs/GaAs bilayer. It was found that if the entire InAs layer is segregated into an InAs/GaAs alloy, this causes the diffraction peaks to weaken as the InAs/GaAs interfaces become less abrupt. It was also found that intermixing causes a significant change in the XRD curve because the amount of GaAs in the InAs/GaAs bilayer structure increases.

In this thesis, the JPEG 2000 quality scalability feature was investigated in thecontext of transporting video over IP networks. The goals of the investigation wastwo-fold. First, it was desired to nd a way of choosing the number of quality layersto embed in a JPEG 2000 codestream. In previous work, this choice has been moreor less arbitrary. Second, it was desired to nd how low the video bitrate could bedropped before it became perceptible to a viewer. This information can be usedin an IP networking scenario to e.g. adapt the video bitrate blindly according tothe measured channel capacity as long as the drop in bitrate is expected to beimperceptible. When the drop in bitrate is expected to be perceptible, a switchcould be made to a smoother bitrate adaptation.A way of choosing the total number of quality layers to embed in a codestreamwas found by minimizing the dierence in predicted quality between direct andscaled compression. Scaled compression is the compression which is achieved byextracting quality layers. The minimization procedure was bound by the speed ofthe encoder, as it takes longer for an encoder to embed more quality layers. It wasfound that the procedure was highly dependent on the desired bitrate range.A subjective test was run in order to measure how large a drop in video bitrate hadto be for it to become perceptible. A newly developed JPEG 2000 quality layerscaler was used to produce the dierent bitrates in the test. The number of qualitylayers to embed in codestream was found by using the minimization procedurementioned above. It was found that, for the bitrate range used in the test, 2 - 30Mbits/s for a resolution of 1280x720 at 25 frames per second, the magnitude ofthe drop in bitrate had to be at least 10 Mbits/s before the participants in the testnoticed it. A comparison with objective quality metrics, SSIM and PSNR, revealedthat it was very dicult to predict the visibility of the drops in bitrate by usingthese metrics. Designing the type of rate control mentioned in the rst paragraphwill therefore have to wait until a parameter with good predictive properties canbe found.

Automatic CFAR Detection is to be implemented in a real time pulsed MTD radar system, used in a mar-itime application.The CFAR should be able to have good detection properties in bad weather conditions, where rough seastates, heavy downpour and high winds are expected.Sucient detection properties may be achieved using an Ordered Statistics based CFAR to generate detec-tion threshold for the MTD radar video signal.The MTD video is the coherent raw video of the signal ltered in a bandpass lter bank, separating theDoppler frequency space of the video into a number of individual Doppler channels.The Doppler frequency shift relates to a velocity, implying that every Doppler channel represents a velocityspace, so that targets and clutter may further resolved by their relative Doppler velocityCFAR algorithms are applied to all the test cells in the MTD video signal. These algorithms have to estimatea threshold that is used at discriminating real targets from clutter in all the velocity channels of the MTDvideo.A good threshold estimate is to have a low probability of false detections, and a high probability of declaringactual targets.This is to be valid in all clutter conditions, even when one or multiple targets are surrounded by non-stationary clutter and closely spaced.The Ordered Statistics algorithms involves using the k'th largest value of the test window as a mean clutterpower estimate for its corresponding test cell.The ordered statistics model makes a threshold selection based on the rank of the samples. A task withcomplexity increasing as a function of window length and k parameter.This task is to be performed on a large number of test cells in a system running real time. In a real timeradar system, all processing have to be done before the next scan becomes available.Radian AS works on developing a PC based MTD Radar system for a pulsed Doppler radar.The radar interfaces the PC through a PCI Express radar receiver card developed by Radian AS.This thesis investigates the application of parallel programming in C/C++ in order to achieve real time au-tomatic detection in a PC based MTD radar. Two means of parallel programming are considered, involvingexploitation of multi core CPU architecture as well as using a dedicated GPU as a co processor.OpenMP is an Open Source library with compiler instructions for running tasks in parallel over multiplecores in a CPU. It is easily incorporated into C/C++ code, and may be used with most multi core CPUs.nVidia has made GP-GPU computing available to the public through CUDA, selling CUDA enabled graphicscards and providing the tools as well as documentation needed for a programmer to be able to use the GPUas co processor.CUDA C integrates the SIMT abstractions of CUDA, and a programmer may write C code that is compiledand executed on the GPU.Dierent implementations of the OS-CFAR algorithm for threshold estimation are implemented using CUDAand OpenMP.The dierent implementations are evaluated and compared to each other in terms of the results gatheredfrom executing them on MTD video.The experiences drawn from this work is concluded with respect to the application of parallel programming,and further recommendations for the future of the project of making a PC based pulsed MTD Radar signalprocessor.This thesis introduces a CUDA algorithm for high throughput ordered selection using short window lengthson a large number of cells under test.An algorithm developed in C for the project assignment leading up to this thesis is enabled openMP, alongwith a C++ STL algorithm, for performing ordered statistics ranked selection on the CPU. In addition, theCUDA OS-CFAR algorithm is ported to C with openMP.The three implementations in C/C++ are compared to the CUDA C implementation.

Pipes with corrugations or cavities are used in a wide variety of applications. In recent years the natural gas industry has experienced "singing" risers, where pipes transporting natural gas excite loud whistling sounds limiting the flow rate of which the gas can be transported. There has been a number of publications regarding this phenomenon, investigating corrugated pipes and pipes with one or more cavities. In this thesis the most basic situation will be studied; A smooth pipe with a single small cavity. This is studied by simulations and experiments. The effects of changing the length of the cavity, and the pipe section between the inlet and the cavity is investigated. The simulations were conducted in Palabos, a Lattice Boltzmann solver which proves to be a promising piece of software for acoustic simulations. The experiments were conduced using a metal pipe with variable inlet and cavity length. Initial vortices created at the inlet are amplified in the cavity by a cavity flow. The results strongly suggest that these inlet vortices are essential for the excitation of whistling sounds. The number of vortices traveling across a cavity at the time is called a hydrodynamic mode. When the frequency of vortices crossing a cavity coincides with an acoustic pipe mode, a whistling sound close to this frequency is excited. Cancellation of the whistling sound with an added cancellation frequency is possible for certain cavity and inlet lengths.

P-type GaAs semiconducting nanowires (NWs) with NW/electrode contacts have been examined by fabricating single NW devices to investigate their electrical properties. Both NWs grown with Au-assisted and Ga-assisted vapor-liquid-solid (VLS) method have been examined, with great emphasis on Ga-assisted NWs because these show superior contact properties. The NWs were grown using molecular beam epitaxy (MBE) and electrical contacts were fabricated using electron beam litography, electron beam evaporation for metallization and annealing to enhance ohmic behaviour of the contacts. Two different types of contacts were tested. One was metal contacts where various combinations of metal layers were tested, including such metallizations as Pt/Ti/Pt/Au and Pd/Zn/Pd/Au. The second electrode type was graphene which is expected to show very interesting electric and optoelectronic properties.It is shown in this thesis that ohmic contact with linear I-V characteristics has been achieved by two different methods. The first being annealing of the NW contact after contact fabrication. The second is by increasing doping concentration during NW growth. It is also shown that Pt/Ti/Pt/Au metallization is the layer configuration that exhibits the best ohmic contact and the most consistency in electrical measurements. 4-probe measurements were also carried out to measure the intrinsic resistivity of the NW, which makes it possible to estimate its doping concentration and carrier mobility.NW/graphene contact was also tried.Mechanical exfoliation of kish graphite was performed to make high-quality graphene, which was selctively placed to make NW contact. However it is found that heating of the EBL-resist during e-beam evaporation caused the graphene to wrinkle and dissolve. CVD-grown graphene on Cu-foil was also tested. Inspection after the graphene transfer proved that the graphene that was used was incontinous and flaky making it difficult to obtain proper contacts to NWs. In addition the NWs connected to graphene probably suffered from over-etching due to multiple etching steps. Since a lot of efforts was put into obtaining a suitable measure of making NW/graphene contacts only preliminary measurements were conducted, so these results has yet to be verified.

A macro-photoluminescence study of self-catalyzed nanowires, using a specializedsetup for this purpose, has been performed. Several samples were even comparedto single nanowire micro-photoluminescence measurements, on the samesamples, done by other students in the nanowire group at NTNU. The macrophotoluminescence measurements were done by changing parameters such as temperature and excitation power. A 532 nm laser was used to excite the wires and thephotoluminescence was measured by a CCD detector attached to a spectroscope.Using macro-photoluminescence measurements in a qualitative comparison withmeasurements done on single nanowires by micro-photoluminescence spectroscopycan give the researcher a decent understanding of the quality of the sample and itscontributions to photoluminescence. Measurements done in this thesis show probablecontributions from most types of transitions expected in zinc-blende nanowires,consisting of such defects as dense zinc-blende/wurtzite heterostructures, highlytwinned regions, but also from nanowires of higher purity.As nanowires move closer to the realization of e.g. nanowire based solar cells,such macro-photoluminescence measurements will become increasingly importantin deciding the overall quality of the grown structures.

In this thesis, single zincblende GaAs nanowires grown by molecular beam epitaxy using the self-catalyzed approach were studied with m-photoluminescence spectroscopy in order to assess the optical quality of self-catalyzed GaAs nanowires grown for the first time at NTNU and to compare the optical properties of self-catalyzed GaAs nanowires with Au-assisted GaAs nanowires and bulk GaAs references. The low temperature and temperaturedependence measurements revealed type II recombinations between zincblende and wurtzite segments occurring at the nanowire tips, however it was established that radiative recombination does not take place in the zincblende GaAs nanowire core. As the thesis progressed, valuable feedback was given to the growers in order to optimize nanowire growth conditions. The thesis builds upon data from earlier work within this project andprovides a foundation for future work on self-catalyzed GaAs nanowire devices at NTNU.

The field of terahertz time-domain spectroscopy (THz-TDS) is still far from reaching its full potential, but is a very promising utility for a wide range of applications. Principle experiments have been performed in fields of drug screening, pharmaceutical, medical diagnostics, security imaging and detection of explosives. Optimized and adapted THz-TDS systems holds great promise for driving this technology further.The purpose of this thesis was to build a THz-TDS system, explore possibilities for improving this system and to perform THz-TDS measurements on semiconductors and wood. The aim of the experimental work was to build a stable and reliable system with an electric field strength of THz radiation in the order of kV/cm. The THz-TDS system used in this thesis was based upon the principles of optical rectification and free-space electro-optic sampling in zinc telluride (ZnTe) crystals using a femtosecond Ti:Sapphire amplified laser.Theoretical studies were performed on the principles of generation and detection of THz radiation. The experimental work was based on publications of similar experiments. Theoretical and experimental studies lead to several modifications and improvements of the setup first built in this thesis. Experiments were performed on disparate materials to find suitable materials for THz transmission. Results from measurements performed on semiconductors and wood, obtained by THz-TDS, were analysed to find the absorption coefficient and the refractive index of the materials. The spectroscopic information obtained by THz-TDS can also be used to find the conductivity and the mobility of these materials. THz-TDS measures the electric field and therefore provides information of both the amplitude and the phase of the THz wave. A Fourier transformation was used to obtain the frequency spectrum of the detected signal. The improvements were done by analysing the results of the detected signal to see which adjustments and modifications to the setup that had positive effects on the results. The pump power used for generation of THz radiation and the optimum azimuthal angle of the ZnTe crystals were crucial to obtain a THz-TDS system with a strong electric field. The maximum electric field strength for the THz radiation in this thesis was 13.2 kV/cm, with a signal-to-noise ratio of 43 and dynamic range of 1500.

The NTNU Test Satellite (NUTS) is planned to have a payload for observation of atmospheric gravity waves. The gravity waves will be observed by means of an infrared camera imaging the perturbations in the OH airglow layer. So far, no suitable camera has been found that complies with the restrictions that follows when building a small satellite. Uncooled InGaAs has however been concluded to be the most suitable detector type in terms of wavelength response and weight.InGaAs sensors are known to have a high dark current when not cooled, and processing must therefore be applied to remove the background offset and noise.The combination of the high speed of the satellite and the long exposure time that is required for the camera will create motion blur. Simulations with synthetic test images in MATLAB showed that the integration time should at least be kept under 1 second in order not to destroy the wave patterns. Longer integration times may however be required in order to get a sufficient SNR.Two signal processing solutions to this problem was investigated: motion blur removal by deconvolution and image averaging with motion compensation. The former strategy is to apply a long exposure time to get a strong signal, and then remove the blur with deconvolution techniques using knowledge of the blur filter.Simulations applying the Lucy-Richardson (LR) algorithm showed that it was not able to remove strong blur, and was very sensitive to errors in the blur filter and noise in the image. The other approach is to obtain a sequence of images with short exposure time in order to avoid motion blur, and provide the necessary SNR by shifting the images according to the known motion and combine them into one image. This concept is simpler and more reliable than the deconvolution approach, and simulations showed that it is less sensitive to errors in the speed estimate than the deconvolution algorithm. It was concluded that this is the most suitable approach for the NUTS application, and it should be implemented on-board the satellite in order to provide a good SNR for the compression to function optimally. The downlink datarate of NUTS is of only 9600 bit/s, and it has been estimated that 2.45 Mb of payload data can be downloaded on average per day. This corresponds to less than 5 uncompressed images of 256 × 256 pixels with 8 bit per pixel.A sequence of overlapping combined images should be obtained to provide a scan of a desired area, and it was suggested that it should be encoded as video to enable efficient compression and transmission of as many images as possible to the ground station. A three-dimensional DPCM algorithm combined with a deadzone quantizer and stack-run coding was implemented in MATLAB. Simulations demonstrated that this simple compression scheme can provide a bit rate of less than 1 bit/px for a sequence of ravity wave images. One of the quantizers that was tried gave 0.83 bits per pixel with reasonable quality. If this number can be achieved in practice, the image transfer ate would be increased to 45 images per day, which is a significant improvement.