Sjöfartsverket har i sitt arkiv en stor mängd backscatterdata, insamlat med multibeamekolod, som ännu inte har använts till sin fulla potential. Backscatterdata innehåller information om den reflekterade signalens styrka, även kallad amplitud. Stora mängder backscatterdata kan användas för att beskriva den akustiska bottenreflektionen. Syftet med denna undersökning är att beskriva hur variationen för amplituden varierar beroende på vilken bottentyp den reflekteras ifrån. En metod för att skapa rasterdataset med bottenhårdhet och bottentyp baserat på amplituddata ska utvecklas. Resultaten från denna metod ska sedan jämföras med kartdata från Sveriges Geologiska Undersökning (SGU). Totalt användes cirka 45 miljoner bottenpunkter i studieområdet. Varje punkt innehåller information om amplitud som systemet har registrerat från det reflekterade ekot. Dessa data behövde genomgå databehandlingar, bl.a. en vinkelkorrigering som ger ett mer trovärdigt värde av amplitud. Med hjälp av befintlig information om studieområdets sjöbotten i form av en maringeologisk karta från SGU, kunde amplitud från ett antal specifika uppskattade bottentyper studeras direkt. Resultatet uppvisar stora skillnader i amplitudens variationer. Specifika medelvärden och standardavvikelser kan urskiljas beroende av vilken specifik uppskattad bottentyp som studerades. ”Mjuk lera” gav en svagare signal med relativt låg standardavvikelse. ”Häll” och ”sten och block” reflekterade en liknade men starkare signal. Amplitudata från backscatter-informationen i hela datamängden utnyttjades för att skapa raster vars syfte var att beskriva den uppskattade bottenhårdheten. Olika raster skapades med olika parametrar beroende på ändamål. Gemensamt för alla skapade raster är att de är uppbyggda med metoden ”flytande beräkning” som möjliggjorde en mer utjämning. Resultatet av medelvärde och standardavvikelse från varje enskild bottentyp utnyttjades för att utföra en klassning av bottentyper på ett skapat raster lämpad för just bottentypsklassificering. För att få ett mer noggrannare medelvärde och standardavvikelse studerades ett 68 % konfidensintervall för de olika bottentyperna. De bottentyper som valdes för klassningen var ”mjuk lera”, ”sand, grus och sten”, ”häll”, ”sten och block” och även ”lägre amplituder”. ”Häll” och ”sten och block” klassades samma eftersom deras fysikaliska egenskaper gör att deras värden ligger nära varandra vilket gjorde det svårt att urskilja dem.”Lägre amplituder” utnyttjades för att identifiera områden som har lägre reflektionsförmåga än mjuk lera. Vilken bottentyp det är kan endast provtagning ge svar på. Med hjälp av tolkning av skapade raster och den maringeologiska kartan så korrigerades intervallen och användes som klassning. Resultatet från klassningen visar tydligt att områden kan urskiljas i kartbilden. Majoriteten av klassningarna resulterade i typen mjuk lera. En jämförelse av klassningen med den maringeologiska kartan visar att stora skillnader finns mellan dem. Mjuk lera gav en överensstämmelse på 86 %, sand, grus och sten 30 % och häll, sten och block 52,5 %, vilket gav en total överenstämmelse på 56,2 %. Jämförelse utfördes även med 9 provtagningspunkter som fanns tillgängliga i området. Det visade en total överenstämmelse på 89 %. Undersökningen visar att amplitud från havsbottnen korrelerar med bottentypen det är. Noterbart är att metoden för bottentypsklassificering som utvecklats i denna studie inte har kunnat kvalitetsgranskas med ett trovärdigt resultat, p.g.a. av statistiskt för få provtagningspunkter att jämföra mot. Studien visar dock att med mer data och noggrannare referensdata kan en mer automatisk klassningsmetod utvecklas. / The Swedish Maritime Administration (Sjöfartsverket) has a large amount of backscatter data collected with multibeam echosounder in their archive that has not been fully used despite its great potential. Backscatter data contains information about the strength of the reflected signal, often called amplitude strength. Large amounts of backscatter data could be used to describe the acoustic bottom reflection. The purpose of this study is to describe how the variation of the amplitude strength varies dependent on which estimated bottom types the data reflects from. Also a method will be produced which purpose is to create gridded dataset of estimated bottom hardness and bottom type based on amplitude data and compare this method with official data from the Geological Survey of Sweden (SGU).A total number of 45 million depths (data points) were used in the study area. Every data point contains information about the amplitude strength that the system has recovered from the reflective echo. This data needed to be preprocessed, including an angle correction that produces a more reliable value of the amplitude strength. With existing information about the bottom from the study area, in this case a marine geological map from SGU, the amplitude from some estimated specified bottom types could be studied. The result shows differences in their variation. Specific values of mean and standard deviation could be distinguished by which estimated specific bottom types that were studied.The amplitude strength from the backscatter information of the complete data set was used to create a raster that describes the estimated bottom-hardness. Different raster were created with various parameters dependent on the purpose. All of the created raster data had in common that it was created using a technique called “flow calculation” which result in more equalization.The mean and standard deviation for every individual estimated bottom type were used to create interval for classification of the bottom types. To achieve a more accurate estimation of the mean and standard deviation for the bottom types, a 68 % confidence interval were used. The classes that were chosen for classification was “soft clay”, “sand, gravel and stone”, “solid rock”, “stone and block” and “lower amplitudes”. “Solid rock” and “stone and block” were combined in the same class because of their similar physical properties. “Lower amplitudes” were chosen in order to indicate areas where the amplitude strength from the reflective echo was lower than “soft clay”.The result of the intervals was adjusted by an examination of the raster data and the marine geological map and was then used for classification.The result from the classification shows that areas of different bottom types could be distinguished in the map. The majority of the classification was of the type “soft clay”. A comparison between the classification and the marine geological map showed some differences. “Soft clay” matched with 86 %, “sand, gravel and stone” 30 %, “solid rock, stone and block” 52,5 % and the total matched with 56,2 %. Comparisons between 9 samplings in the area were made. The result shows that the classification-accuracy is 89 %.The study shows that the amplitude strength correlates to the bottom type. Note that too few samplings for bottom classification were used in the study and thus the results are not fully reliable. The study, however, shows that with larger amount of data and more accurate reference data a better automatic classification method could be developed.

La rétrodiffusion associée aux effets de géométrie de surface à des angles d’incidence élevés (62°—76°) et pour quatres angles azimutaux (Q0, 3Q0, 60° et 90°) a été étudiée pour des champs de maïs du Québec (Canada) à l’aide de 3 images du ROS-C du Centre canadien de télédétection. Selon les conditions de drainage des champs, le couvert végétal apporte une plus ou moins grande contribution à la rétrodiffusion. L’effet de géométrie de surface est nettement plus prononcé (amplitude 3,2 dB) pour les champs de maïs sans drainage souterrain que ceux ayant un drainage souterrain (1,5 dB). Le contraste entre ces deux types de champ est rattaché aux différences de pente du couvert végétal ainsi qu’aux variations de biomasse.

Understanding the plastic deformation mechanisms in polycrystals is a long-standing fundamental problem and its improvement has significant potential impact on the increase in materials resistance to typical failure modes such as fatigue cracking and stress corrosion cracking and hence the increase in the materials strength. However many deformation models are yet to be validated as quantitative experimental results at mesoscale to correlate dislocations and microstructure features are limited. This thesis furthers the High Resolution EBSD (HR-EBSD) technique in Geometrically Necessary Dislocation (GND) density measurement from qualitative analysis with a typical map size of 100 μm x100 μm to quantitative analysis with a map of 500 μm x500 μm by determining the optimised scanning step size (0.5 μm) and detector binning level (4x4 binning). This allows a statistically large number of grains to be sampled. Combining with obtained crystallographical information from a conventional EBSD system, systematic studies on GNDs behaviours with respect to a range of microstructure features such as grain boundaries and triple junctions were conducted on monotonically deformed polycrystal copper samples under tension. Relatively high GND density points were found near triple junctions and some grain boundaries whereas the low GND density points tend to appear near the grains’ interiors. These tendencies are particularly profound in low and moderately deformed samples. Hence more detailed analyses were performed to investigate the relations of GND density and the properties of grain boundaries and triple junctions. These quantitative analyses were complemented with direct visual assessment. The visual inspection provides interesting findings such as the strong GND structure dependence on grain orientations and GND structure development through increasing deformation; grain-grain interaction influences on GND structure development and GND structures near triple junctions. These GND density studies provide experimental results to validate some of the existing plastic deformation models for instance Ashby’s model of hardening and Hall-Petch relation. However, some of the new observations on GND structures at mesoscale cannot be fully rationalised by existing proposed mechanisms. Hence new models have been proposed that these GND structures might be generated from the intersections of different slip systems which occurred in various parts of a grain, or by the dislocation piling-up at some microstructural features e.g. triple junctions and twin boundaries.

Cette étude se place dans le cadre du guidage des thérapies par ultrasons focalisés de haute intensité (HIFU). L’utilisation de l’échographie pour le guidage permet une visualisation temps réel mais un faible contraste. Afin de compenser ce manque de vision du traitement, deux études ont été mises en place. La première sur l’utilité de l’élastographie par compression manuelle en temps réel (23 à 60 images par seconde) a été réalisée et validée par deux protocoles in vivo. L’un a été effectué afin de visualiser des tumeurs VX2 dans le foie chez le lapin de manière extracorporelle et per-opératoire en utilisant une sonde de diagnostique linéaire (12MHz). L’autre a été réalisé sur des porcs avec la même sonde et avec une sonde d'imagerie sectorielle (7,5 MHz) placée au centre du transducteur HIFU. Une comparaison a été menée avec des images IRM des mêmes lésions réalisées après prélèvement de l’organe traité. Dans les deux cas, les élastogrammes assurent une meilleure visualisation des dimensions de la lésion (R=0,70) et un contraste plus important (23dB) en comparaison de l’échographie (R=0,65, contraste=3dB). La dernière partie de ces travaux a permis de démontrer que le signal ultrasonore rétrodiffusé par les tissus du foie change avec la température. Lors d’expériences in vitro et in vivo sur du foie de porc, ce changement de signal se corrèle (R=0,85) avec une hausse de température mesurée par un thermocouple positionné dans la zone focale du transducteur. Cette relation est linéaire positive in vitro et négative in vivo. Cette relation permet de calculer des images de température sur une plage de température allant de 20 à 100°C avec une précision de 5°C. / This study takes place under the guidance of high intensity focused ultrasound therapies (HIFU). The use of ultrasound for guidance allows real time monitoring, but low contrast. To compensate this lack of vision, two studies were set up. The first set up was used to evaluated usefulness of hand-held elastography in real time (23 to 60 frames per second) performed and validated by two in vivo protocols. One was performed to visualize VX2 tumors in the rabbit liver so extracorporeal and intraoperative using a diagnostic linear probe (12MHz). The other was carried out on pigs with the same probe but also with a sectorial imaging probe (7.5 MHz) placed in the center of the HIFU transducer. A comparison was conducted with MRI images of the same lesions performed after removal of the treated organ. In both cases, elastograms provide better visualization of the lesion size (R = 0.70) and higher contrast (23dB) compared to ultrasound (R = 0.65, contrast = 3dB). The last part of this work demonstrated that the ultrasound backscattered signal of the liver tissue changed with the temperature. In experiments on in vitro and in vivo pig livers, this changed of signal is linear and correlated (R = 0.85) with a rise in temperature measured by a thermocouple positioned in the focal zone of the transducer. The relation between backscattered signal and temperature is positive in vitro and negative in vivo. This relationship is linear and used to calculate temperature images with a range of 20 to 100 ° C and an accuracy of 5 ° C.

In this thesis, we show that it is possible to design a battery-free light sensing system that can sense and communicate hand gestures while operating fully on harvested power from indoor light. We present two main innovations that push our system to tens of microwatts of power to enable battery-free operation. First, we introduce a novel visible light sensing system that can track variations in light intensity by using a solar cell as a sensor. Solar cells are unlike photodiodes optimized for energy yield in the visible light region and hence do not require any power hungry active components such as an operational amplifier. Furthermore, solar cells can operate under more diverse light conditions as they are not susceptible to saturation under bright light. Second, we devise two ultra-low power communication mechanisms based on radio frequency backscatter to transmit sensor readings at various resolutions without the need of any energy-expensive computational blocks.  We design two battery-free and self-powered hardware prototypes that are based on these two innovations. Our first design utilizes an on-board comparator based circuit to perform a 1-bit digitization of changes in light readings, consuming only sub-microwatt of power for digitization. For our second prototype, we design an analog backscatter mechanism that can map raw sensor readings directly to backscatter transmissions. We demonstrate the feasibility of our designs when sensing significant changes in light intensity caused by shadows from hand gestures, and reconstruct these at a receiving device. Our results demonstrate the ability to sense and communicate various hand gestures at a peak power of 20 microwatts when performing 1-bit digitization, and a mean power of 60 microwatts when performing analog backscatter. Both designs represent orders of magnitude improvement in terms of power consumption over state-of-the-art visible light sensing systems. / Battery-free Visible Light Sensing / MobiCom: G: Battery-free Visible Light Sensing

A travers cette thèse, nous avons cherché à développer de nouvelles méthodes de mesure, basées sur la rétrodiffusion acoustique, pour estimer la concentration massique des sédiments en suspension dans les rivières. Souvent, ces sédiments présentent une distribution granulométrique bimodale, i.e. constituée d’un mélange de sédiments fins et de sable. Le principal avantage des méthodes hydroacoustiques est leur capacité à fournir des mesures avec une résolution spatiale et temporelle bien meilleure que les techniques classiques type prélèvement. L’objectif est in fine d’améliorer l’estimation du flux sédimentaire dans les cours d’eau. Des mesures acoustiques multifréquences, associées à des prélèvements physiques, ont été réalisées sur le terrain et dans une cuve expérimentale au laboratoire. Des méthodes d’inversion du signal acoustique ont été testées et développées au laboratoire sur une suspension homogène de sédiments fins. Une nouvelle méthode en particulier, combinant analyse de la rétrodiffusion et de l’atténuation acoustique, a permis de retrouver la concentration massique des sédiments avec une précision de l’ordre de ± 20 %. En rivière, une méthode mixte alliant données de calibration et inversion du signal acoustique à deux fréquences a été développée, permettant, dans certaines conditions, d’estimer la concentration des sédiments fins et du sable sur l’ensemble de la section en travers d’un cours d’eau. Ce résultat confirme la capacité de la technologie hydroacoustique à fournir une information spatiale sur la suspension. Des écarts parfois importants ont été observés entre la réponse acoustique théorique, calculée à partir des données de concentration et de granulométrie, et les mesures acoustiques sur le terrain. Il semble que ces écarts soient dus à la présence d’autres corps diffusants dans les rivières, probablement des flocs et/ou des micro-bulles d’air. Ces travaux appellent au développement d’un cadre théorique plus performant et adapté aux suspensions rencontrées en rivière. / With this PhD, we have tried to develop new measurement methods, based on acoustic backscattering, to estimate the mass concentration of suspended sediments in rivers. These sediments often show a bimodal grain-size distribution, i.e. composed of a mixture of fine and sand particles. The main advantage of hydroacoustic methods is their ability to provide measurements with a much better spatial and temporal resolution than conventional sampling techniques. The ultimate goal is to improve the sediment load estimation in rivers. Multifrequency acoustic measurements, combined with physical sampling, were carried out in the field and in an experimental laboratory tank. Acoustic inversion methods were tested and developed on a homogeneous suspension of fine sediments in the laboratory. A new method was implemented, combining the analysis of acoustic backscatter and attenuation, and led to retrieve the sediment mass concentration with a precision in the order of ± 20%. In rivers, a semi-empirical method combining calibration data and acoustic inversion at two frequencies has been developed, allowing, under certain conditions, to estimate the concentration of fine and sand sediments throughout the entire river cross-section. This result confirms the ability of hydroacoustic technology to provide spatial information on the suspension. Significant differences were frequently observed between the theoretical acoustic response, computed from concentration and particle size data, and the acoustic measurements in rivers. It seems that these differences could be due to the presence of other scatterers in rivers, probably flocs and/or air micro-bubbles. This work calls for the development of a more efficient theoretical framework suitable for river suspensions.

Karenia brevis, a toxic dinoflagellate species that blooms regularly in the Gulf of Mexico, frequently causes widespread ecological and economic damage and can pose a serious threat to human health. Satellite-based ocean color imagery may provide a means for detecting and monitoring blooms, providing early alerts to coastal communities. However, a technique for discriminating K. brevis from other chlorophyll-containing algae is required. Between 1999 and 2001, a large bio-optical data set consisting of spectral measurements of remote-sensing reflectance (Rrs(lambda)), absorption (a(lambda)), and backscattering (bb(lambda)) along with chlorophyll a concentrations was collected on the central west Florida shelf (WFS) as part of the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) and Hyperspectral Coastal Ocean Dynamics Experiment (HyCODE) programs. Reflectance model simulations indicate that cellular pigmentation is not responsible for the factor of 3 to 4 decrease in Rrs(lambda) observed in waters containing greater than 104 cells 1-1 of K. brevis. Instead, particulate backscattering coefficients measured inside K. brevis blooms are responsible for this decreased reflectivity as they were significantly lower than values measured in high-chlorophyll (>1 mg m-3), diatom-dominated waters containing fewer than 104 cells 1-1 of K. brevis. A paucity of high-backscattering detritus present in K. brevis blooms caused by decreased grazing pressure perhaps due to cellular toxicity along with a general inability of K. brevis to out compete diatoms and bloom in high-nutrient, high-backscattering estuarine waters may explain this low backscattering. A classification technique for detecting high-chlorophyll, low-backscattering K. brevis blooms is developed. In addition, a method for quantifying chlorophyll concentrations in positively flagged pixels using fluorescence line height (FLH) data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) is introduced. Both techniques are successfully applied to Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and MODIS data acquired in late August 2001 and validated using in situ K. brevis cell concentrations.

<p>This thesis project describes how the retrieval of aerosol extinction and backscatter coefficients is computed from data obtained with a Raman lidar at FOI, Swedish Defense Research Agency. The theory is described, the implementation is done and problems discovered along the way are discussed. The lidar use the wavelength 355 nm and the Raman shift in nitrogen at 387 nm.</p><p>The retrieved algorithm gives extinction coefficient between 1 500 and 10 000 meters while the backscatter coefficient covers the span 800 to 15 000 meters. However there is skewness in the backscatter coefficient that needs to be further investigated. Tests indicate that the skewness comes from the way the measurements are done at FOI.</p>

This thesis project describes how the retrieval of aerosol extinction and backscatter coefficients is computed from data obtained with a Raman lidar at FOI, Swedish Defense Research Agency. The theory is described, the implementation is done and problems discovered along the way are discussed. The lidar use the wavelength 355 nm and the Raman shift in nitrogen at 387 nm. The retrieved algorithm gives extinction coefficient between 1 500 and 10 000 meters while the backscatter coefficient covers the span 800 to 15 000 meters. However there is skewness in the backscatter coefficient that needs to be further investigated. Tests indicate that the skewness comes from the way the measurements are done at FOI.

A 3-axis acoustic Doppler Velocimeter (ADV) with high sampling rate was used to measure the bed shear stress and turbulence under wave-current interaction conditions in this study. Experimental sites include laboratory tank, Love River in Kaohsiung and Howan coastal waters in Pingtung. Bed shear stress is estimated primarily by the inertial dissipation method, also by the turbulent kinetic energy method and eddy correlation method. Results of the laboratory experiments indicate that the bed shear stress increases as both the flow speed and wave height increase, and the flow speed is a more important factor. Field experiments can be divided into several types. The first type is under slow flows and calm waves. Love River is a typical condition of this type with turbid waters and a low flow speed. During the experimental period the ADV correlations reach 90% or more. Because the river flow is quite small, no significant bed shear stress is produced and u* is mostly less than 1 cm/s. As a result the deposition effect is much larger than erosion, thus a very thick layer of mud is formed on the riverbed. The observations in Howan in April 2010 also reveal the condition of slow flows and small waves, and the bed shear stress is also quite small. Due to the factors of clean coastal waters and weak turbulence in this season, the quality of ADV signals is poor. The second type is under large flows and small waves, as shown from the observations of Howan in April 2011, during which the maximum speed reached 25 cm/s and wave heights less than 20 cm. In this experiment the shear stress is large, the u* are mostly greater than 0.8 cm/s and the value of the drag coefficient is 0.0021; the ADV signals have good quality and the inertial sub-range is well defined. The third type is under weak flows and large waves. The observations of Howan in July 2011 show significant rainfall and maximum wave heights of 90 cm. In this case the u* are mostly centered around 1 cm/s. The acoustic backscatter intensity is positively correlated with the turbidity and wave height. Sizable bed shear stress induced by the orbital velocity of waves contributes a significant part to the total bed shear stress.