The internal tide in GPSC¡]Gaoping submarine canyon¡^is the main factor controlling the movement of watermasses. In order to improve our understanding on the compact of suspended sediment exchange in and out GPSC, the data used in this study are collected from four cruises of field observations using research vessel OR3. Instruments deployed include ADCPs¡BEK500¡BCTD and vertical string of temperature loggers. The collected data are analyzed through a variety of time series analysis technique, such as harmonic analysis¡BFFT and EOF. The results show that¡]1¡^the echo intensity recorded by ADCP through calibration could reduce the decay of echo with the distance. The results seem useful to apply in watermass behavior studies.¡]2¡^ Echo intensity with calibration were comparable with signal recorded by EK500 which could be validated to each other. These observations were related to sediment resuspension influenced by internal tide. ¡]3¡^There were two layers of large turbidity, at the depth of canyon edge and near the bottom of canyon, both were fluctuated with two interval tidal frequency.¡]4¡^Another band of echo intensity fluctuations, not directly correlate to sediment resuspension, was likely due to vertical migration, of zooplankton or biology effects.

As the size and power consumption of microelectronic circuits continues to decrease, passively-powered sensors promise to come to the forefront of commercial electronics. One of the most promising technologies that could realize this goal is backscatter sensing. Backscatter sensors could harvest power from and modulate data onto an impinging carrier waveform. Currently radio frequency identification (RFID) technology passively powers itself and transmits statically stored data. However, this technology has two major weaknesses: lack of resiliency against narrowband interference and slow data rates. Both of these issues could be detrimental in sensing applications. This thesis will lay out a method for addressing both of these weaknesses through a unique application of spread spectrum encoding. Instead of spread spectrum being viewed as the multiplication of an already encoded data sequence with a periodic pseudorandom sequence, each sequence could be viewed in an aperiodic manner, where a single period of a pseudorandom sequence represents a data symbol. In this manner, backscatter sensors not only benefit from the increased resiliency that spread spectrum provides, but also can have higher data rates, since multiple bits can be encoded on a single symbol and multiple nodes can be read simultaneously, using spread spectrum multiple access techniques. In this thesis, 63-chip and 255-chip Kasami sequences, as well as 127-chip Gold sequences, will be analyzed for their use in various aperiodic direct sequence spread spectrum/multiple access system configurations (systems that have up to three nodes and use up to four different aperiodic sequences per node to represent different symbols). For each different configuration, near-"ideal" code configurations/rotations will be determined for use in the system.

A quadrature phase shift keying (QPSK) retrodirective array phase modulator (RAPM) was designed and fabricated to characterize its backscatter signal constellation when placed near objects with varying conductivities and relative permittivities. The signal constellations produced when the RAPM was placed near objects were compared to a constellation in free space to determine relative magnitude and phase changes. When conductors and high permittivity dielectrics were placed close behind the RAPM, constellation points were found to shrink in magnitude by up to twenty percent and shift in phase by up to eight degrees. When conductors were placed between the RAPM and an interrogator, the signal constellation was found to collapse, shrinking by up to 95.6 percent. For materials similar to free space, minimal constellation shrinkage resulted, but signal constellation rotation by up to 68 degrees occurred. The power consumption of a RAPM was also characterized and found to decrease as the number of bits per symbol increased. This result demonstrates that in comparison to conventional backscatter tags, which implement one bit per symbol, the RAPM can implement a greater number of bits per symbol, reduce its power consumption, and increase its range in a passive backscatter communication system. To characterize the beamwidth of the RAPM's retrodirective array, a radar cross section (RCS) measurement of the RAPM was performed over a scan angle range of -90 to +90 degrees. The structural component generated by the RAPM's patch antenna ground plane was found to dominate the antenna mode of the retrodirective array. As a result, a novel homodyne receiver based RCS measurement was performed to filter out the structural RCS component and measure the pure antenna mode of the RAPM.

Depuis quelques années le nouveau paradigme d'internet des objets, qui se traduit par la connexion des objets de la vie quotidienne à internet grâce à des dispositifs électroniques intégrés, est devenu plus qu'un simple concept et a commencé à entrer dans la réalité. Il en est ainsi des systèmes d'identification par radiofréquence (RFID), qui font partie des technologies disponibles. Lorsque le coût et la taille des tags deviennent des exigences prépondérantes, l'adoption de tags (semi-)passifs fondés sur la modulation d'un signal rétrodiffusé représente une solution attractive. En outre, l'utilisation de techniques ULB apporte des avantages propres à favoriser le remplacement d'une partie des systèmes RFID actuels qui souffrent de certains défauts tels qu'une trop forte consommation ou une faible robustesse en présence d'interférence. La thèse de doctorat se place dans ce contexte: elle a pour objectif l'étude des systèmes ULB RFID semi-passifs et se situe dans le cadre du projet européen SELECT, qui vise à développer et à évaluer un tel système. La prise de conscience qu'il était fondamental de comprendre les mécanismes électromagnétiques intrinsèques à la communication lecteur-tag, préalablement à la conception du système, s'est traduite par la mise en oeuvre d'une collaboration franco-italienne dans le cadre d'une cotutelle de thèse. C'est donc au départ autour d'une analyse fine et d'une modélisation des aspects antennaires et du canal radio entre le lecteur et le tag que la 1re partie du travail s'est construite. La 2nde partie a exploité ces travaux pour l'élaboration des schémas de modulation et de codage du lecteur et du tag pour les systèmes semi-passifs.

No description available.

The ability to generate three dimensional (3D) microstructures in solids is of great importance in understanding their true nature, as it eliminates speculation about the spatial distribution of features associated with conventional two dimensional (2D) imaging techniques. There are several recently-developed 3D techniques for determining the spatial distribution of microstructural features, each with a given resolution. There is considerable interest in the development of a specific serial sectioning methodology, termed 3D electron backscatter diffraction (3D-EBSD), which combines a focused ion beam (FIB) with EBSD interfaced to a field emission gun scanning electron microscope. Here, FIB is used as a serial sectioning device for cutting parallel slices of single- and multi-phase materials with a site-specific accuracy of up to 50 nm. Each consecutive slice is mapped by EBSD and the complete dataset combined using advanced computer algorithms to generate a volume of a material whereby the true crystallographic features can be analyzed at submicron resolution. The aims of the thesis was to develop 3D-EBSD into a powerful materials analysis tool and use it to resolve several issues concerning the nature of the deformed state and the nucleation and the growth behaviour of recrystallizing grains. The study commenced with an investigation into the effect of material type (restricted to face centred cubic AI, Cu and Au metallic crystals), FIB milling conditions and EBSD software variables on the quality of EBSD patterns generated on ion-milled surfaces of these materials. The effect of material type on EBSD pattern quality following FIB milling was found to be significant with relatively poor quality EBSD patterns obtained for metals of low atomic number. It was demonstrated, particularly for the high atomic number metals, that moderate FIB milling currents (~1-5nA) generated good quality EBSD maps from a given ion-milled surface. This preliminary work was necessary for balancing the time required for serial sectioning during 3D-EBSD and the generation of sufficient quality EBSD maps from each ion-milled surface. The outcomes of this investigation were applied to two major 3D-EBSD investigations on the microstructural and crystallographic characteristics of: (i) deformation features generated in a cold rolled interstitial free (IF) steel, with particular emphasis on the formation of microbands; and (ii) recrystallization of a cold rolled nickel alloy containing coarse (>1 ??m) silica particles, with particular attention given to the generation of particle deformation zones and their influence on nucleation and growth of recrystallizing grains including particle stimulated nucleation (PSN), twin formation during PSN and the growth behaviour of various types of grain boundary into the deformation microstructure. The foregoing 3D-EBSD studies were significant as they revealed various microstructural and crystallographic features not usually clearly evident in conventional 2D micrographs obtained by either EBSD or optical metallography. For example, the technique demonstrated that microbands in cold rolled IF steel consist of irregular curved surfaces that reconcile findings that microbands straight and aligned parallel to slip planes when viewed in normal direction-rolling direction sections but are wavy in transverse direction-rolling direction sections. Three slip planes were found within the angular range of the curved surface of the microband, which indicates that multiple slip planes are operative during deformation. The work also showed the influence of particle diameter on the misorientations generated within particle deformation zones and clearly showed that particle stimulated nucleation (PSN) occurred at particles greater than 1.5-2 ??m. It was observed that PSN in the nickel sample also generates contiguous grains separated by both coherent and incoherent twin boundaries and, on further growth of these grains into the matrix, the coherent boundary dominates and remains parallel to the primary growth direction of the grains.

Tidally-influenced sandwaves are common coastal features present in various settings, including shipping channels. The main shipping channel in Tampa Bay under the Bob Graham Sunshine Skyway Bridge (a.k.a. the Skyway Bridge) contains such sandwave bedforms. Between the years 2000 and 2017, these bedforms have been surveyed with multibeam echosounders (MBES) on 21 occasions with ranging coverage and quality of returns. Surveys between 2000 and 2009 used a 300 kHz Kongsberg EM3000; surveys between 2015 and 2017 used a 400 kHz Reson Seabat 7125. For comparable surveys, bathymetry, backscatter, slope, curvature, planform curvature, and profile curvature maps were created and analyzed. Spectral analyses were completed on the same cross-section for usable surveys, providing a period and amplitude for the bedforms. Sediment samples were taken in September 2015 using a Shipek grab. The sediment samples were analyzed for grain size and carbonate content. A bottom-mounted ADCP recorded velocity data semi-continuously over the same time period. These data were analyzed in an effort to investigate the forcing mechanisms that influence the bedform morphology. Mean grain sizes in the shipping channel under the Skyway Bridge range from 0.01 φ (0.99 mm, coarse sand) to 1.55 φ (0.34 mm, medium sand). Calcium carbonate content ranges from 25% to 87%. The sediment sample site most representative of the sandwave bedforms has a mean grain size of 0.01 φ and a calcium carbonate content of 87%. The calculated mean current velocity required to initiate transport of the D50 and D84 grain size percentile of the representative sediment sample site is 0.70 m/s and 1.05 m/s, respectively. Analysis of the ADCP-recorded velocity data shows that the calculated D50 critical velocity is frequently reached by peak flood and peak ebb currents except during neap tides, while the D84 critical velocity is reached only intermittently, mostly during spring tides. Analysis of MBES backscatter shows similar spatial patterns in two larger MBES surveys in 2004 and 2015. Bathymetric analysis of the sandwaves shows consistent characteristics through time. Wave crest analysis reveals that bedforms migrate in both the ebb and flood directions. Spectral analysis shows primary wave spatial frequencies range from 0.13 m-1 to 0.22 m-1, and primary wave periods range from 4.5 m to 6.0 m. The predominant wavelength of sandwaves within the study area is about 5 m, with an average wave height of 0.47 m. The maximum wave height along the axial cross-section analyzed is 0.8 m, observed in April 2017. The sediments comprising the sandwave bedforms are likely winnowed by tidal currents resulting in larger grain size and carbonate content than other areas of the shipping channel and surrounding bay. Consistent patterns in MBES backscatter over time indicate that the sediment distribution pattern in the study area have not significantly changed. The size and shape of the bedforms in the shipping channel beneath the Skyway Bridge are have been in a quasi-dynamic equilibrium over the past 13 years. The bedforms are shown to migrate in both the ebb and flood directions despite an average faster ebb current velocity than a flood current velocity. More frequent and consistent MBES surveys as well as more continuous ADCP data availability would allow for better understanding of sediment transport via bedform migration in tidally-influenced environments.

O propósito geral desta tese foi modelar a dinâmica do retroespalhamento SAR-X ao longo de um pacote superficial de neve seca através do uso de uma ferramenta computacional de modelagem de micro-ondas (RF Module®, PDETOOL®, MATLAB®), baseado na física da interação entre o feixe de micro–ondas e este pacote de neve, e executar a aplicação de métodos estatísticos para geração de relações entre variáveis estratigráficas desse pacote de neve e o respectivo retroespalhamento SAR-X observado. Para tanto, o presente trabalho buscou avançar na organização de um modelo analítico para o processo de interação entre um feixe de micro–ondas na banda X e o pacote de neve superficial, aplicando ferramentas computacionais para a resolução dos equacionamentos que compõem esse problema. Como área de estudo, delimitou–se a porção ocidental antártica, especificamente junto à área da geleira Union. O modelo de retroespalhamento utilizado pautou–se na consideração do Modelo de Transferência Radiativa (MTR), adotando como variáveis principais a profundidade da neve acumulada, a rugosidade da superfície (interface ar–neve e neve–sologelo), o tamanho dos cristais de neve (tamanho dos grãos), o perfil de densidade da neve acumulada e as características das camadas de neve que formam o pacote de neve superficial (espessura, forma da interface entre camadas, variação dielétrica entre camadas, dentre outros). Posteriormente, através da reversão modelagem estatística do modelo de retroespalhamento criado, foram obtidos dados estratigráficos indiretos modelados (número médio de camadas de neve, densidade média do pacote de neve superficial e tamanho médio dos grãos de neve), permitindo a inferência de variáveis da estratigrafia local a partir de dados de retroespalhamento SAR COSMO–SkyMed, banda X. Por fim, a comparação entre os valores modelados e aqueles observados em campo para a estratigrafia e para o retroespalhamento permitiram estimativas do desempenho da modelagem proposta. Para fins de validação desta modelagem, foram considerados dados comuns de entrada, constituídos de dados estratigráficos e de temperatura da neve em um perfil de 2 m de profundidade e dados SAR–X COSMO–SkyMed (modo de aquisição Stripmap/Himage com resolução espacial de 3x3 m) na banda X coletados na região da geleira Union no verão antártico de 2011–2012. Como resultados, foram obtidas equações analíticas para estimativa do tamanho médio dos grãos de neve, número médio de camadas espalhadoras e densidade média do pacote de neve superficial a partir de dados de retroespalhamento SAR– banda X, com consistência estatística mínima estimada de 86% (R² ≥ 86%). Já o modelo de retroespalhamento utilizado, tendo seus resultados comparados aos dados de retroespalhamento in situ COSMO–SkyMed exibiram estimativas com R² da ordem de 90% ou maior, o que é considerado estatísticamente adequado. Este trabalho traz como contribuição a implementação computacional via ferramenta de modelagem de um modelo de retroespalhamento SAR–X, voltado para massas de neve seca, e propõe a obtenção de dados estratigráficos a partir de dados de retroespalhamento SAR–X com o uso de equações determinadas por regressão estatística. Isto permitiu a espacialização de variáveis estratigráficas em zonas de neve seca a partir de dados SAR obtidos ao longo da banda X. Cabe ressaltar o fato de que devido ao limitado número de amostras de campo (7 amostras), a consistência estatística e a confiabilidade dos resultados deve ser tomada com ressalva, quando considerada a análise glaciológica da variação nos parâmetros do pacote de neve, cabendo melhores testes e análises em sua aplicação. / The present thesis proposes an analytical model for interaction between a beam of microwaves in the X band and surface snowpack. To this end, statistical analysis were performed with SAR-X backscattering data and reference data from snowpits focusing the interaction between the microwave beam and the snowpack in dry snow areas. Numerical methods were employed for solution of differential equations that make up this issue. The model was proposed for Union Glacier, located in the West Antarctic Ice Sheetregarding a study area including the Antarctic western portion, recognized as the Union Glacier. The backscattering model used was based under the assumption of the Radiative Transfer Model (RTM), considering as main variables the depth of accumulated snow, the surface roughness (air-snow interface and snow-ice interface), the size of snow crystals (grain size), the density profile of the accumulated snow and snow characteristics of the layers forming the surface snowpack (thickness, shape of the interface between layers variation between dielectric layers, among others). After that, reversal statistical modelling of backscatter was performed to estimate stratigraphic parameters of the snowpack usingdata allowing the local stratigraphy of estimated variables SAR backscatter data from COSMO-SkyMed satellite. To validate the proposed model, the same input data were considered for all experiments performed experiments. These data were made up of snow stratigraphic data and snow temperature data in a 2 m depth glaciological profiles (snowpits) 2m depth and data SAR-X COSMO-SkyMed X-band SAR data (acquisition mode Stripmap / Himage with 3x3 m spatial resolution 3x3 m) acquired atin Union Glacier snowpits and remote sensing SAR data during summer 2011-2012. The results showed average density of the snow pack surface from SAR-X backscatter data SAR-X with R² ≥ 86%. The main contribution of this work is the resulting model for SAR-X backscattering for dry snow masses, which was proved to be statistically consistent with the ground truth data. Even with limited reference data, this result indicates the soundness of the proposed approach, allowing the estimation of spatial distribution ofvariations in stratigraphic parameters of the snowpack variables in dry snow areas from SAR X-band SAR data over the X band. However, snowpack parameters estimated by the method should be used carefully, as the input data used for model development may underestimate all possible variations found at the snow surface of Union Glacier.

Current marine navigation radars are capable of high-resolution imagery of marine ice but are not able to classify the marine ice. Classifying marine ice means identifying the ice as first-year ice, multi-year ice or glacier ice. The latter two ice types are as hard as concrete and capable of damaging even ice hardened vessels such as icebreakers. The Canadian Coast Guard has identified the ability of marine navigation radars to classify marine ice as the single greatest improvement to be made in the safety of Arctic navigation. This thesis presents new research that improves our understanding of electromagnetic backscatter from marine ice. The goal of this work was two-fold: to demonstrate the feasibility of using commercial computational electromagnetic modelling software to simulate real-world marine ice targets, and to identify an optimum frequency or range of frequencies at which the marine ice targets can be definitively classified. Engineering models for scattering from electrically large objects made of a highly variable, complex, heterogenous, three-phase mixture of ice, air and brine are developed. To do so, an extensive literature review of the Arctic environment, and the physical and electrical properties of marine ice, is conducted to distill the required geophysical parameters of the three marine ice types of interest in this work. Using well-established dielectric mixing theory, these parameters are applied to homogenize the marine ice and model the target (in the presence of a flat sea halfspace) using a surface integral equation formulation. To reduce the computational resources required to numerically solve the integral equation models using the method of moments, computational electromagnetic modelling studies are conducted to select a suitable seawater halfspace representation and determine if the properties of larger objects can be inferred from scaled down models of the object. A case study is presented for backscatter from marine ice from 6 to 10 GHz, which explores the effects of frequency on the co- and cross-polarized backscatter intensity (and hence the apparent radar cross-section) of the three marine ice types of interest. Good agreement is found between the co- and cross-polarized backscatter intensity responses found from the engineering model computations and some existing experimental data from real-world marine ice targets. This work: (a) proves the feasibility of using computational electromagnetic modelling to simulate real-world marine ice targets, providing a new, cost-effective method for the study of backscatter from marine ice; (b) confirms the viability of using cross-polarization as a method of classification; and (c) identifies 10 to 16 GHz as a potential optimal frequency range for the classification of marine ice using dual-polarization radar.

Following the continually increasing demand for high-density interconnection and multilayer packaging for chips, solder bump size has decreased significantly over the years, this has led to some challenges in the reliability of interconnects. This thesis presents research into the resulting effects of miniaturization on the interconnection with Sn-solder, especially focusing on the full intermetallics (IMCs) micro-joints which appear in the 3D IC stacking packaging. Thereby, systematic studies have been conducted to study the microstructural evolution and reliability issues of Cu-Sn and Cu-Sn-Ni IMCs micro-joints. (1) Phenomenon of IMCs planar growth: The planar IMCs interlayer was asymmetric and composed of (Cu,Ni)6Sn5 mainly in Ni/Sn (2.5~5 μm)/Cu interconnect. Meanwhile, it was symmetric two-layer structure in Cu/Sn (2.5~5 μm)/Cu interconnect with the Cu3Sn fine grains underneath Cu6Sn5 cobblestone-shape-like grains for each IMCs layer. Besides, it is worth noticing that the appearance of Cu-rich whiskers (the mixture of Cu/Cu2O/SnOx/Cu6Sn5) could potentially lead to short-circuit in the cases of ultra-fine ( < 10 μm pitch) interconnects for the miniaturization of electronics devices. (2) Microstructural evolution process of Cu-Sn IMCs micro-joint: The simultaneous solidification of IMCs interlayer supressed the scalloped growth of Cu6Sn5 grains in Cu/Sn (2.5 μm)/Cu interconnect during the transient liquid phase (TLP) soldering process. The growth factor of Cu3Sn was in the range of 0.29~0.48 in Cu-Cu6Sn5 diffusion couple at 240~290 °C, which was impacted significantly by the type of substrates. And the subsequent homogenization process of Cu3Sn grains was found to be consistent with the description of flux-driven ripening (FDR) theory. Moreover, Kirkendall voids appeared only in the Cu3Sn layer adjacent to Cu-plated substrate, and this porous Cu3Sn micro-joint was mechanically robust during the shear test. (3) Microstructural evolution of Cu-Sn-Ni IMCs micro-joint: There was obvious inter-reaction between the interfacial reactions in Ni/Sn (1.5 μm)/Cu interconnect. The growth factor of (Cu,Ni)3Sn on Cu side was about 0.36 at 240 °C, and the reaction product on Ni side was changed from Ni3Sn4 into (Cu,Ni)6Sn5 with the increase of soldering temperature. In particular, the segregation of Ni atoms occurred along with phase transformation at 290 °C and thereby stabilized the (Cu,Ni)6Sn5 phase for the high Ni content of 20 at.%. (4) Micro-mechanical characteristics of Cu-Sn-Ni IMCs micro-joint: The Young s modulus and hardness of Cu-Sn-Ni IMCs were measured by nanoindentation test, such as 160.6±3.1 GPa/ 7.34±0.14 GPa for (Cu,Ni)6Sn5 and 183.7±4.0 GPa/ 7.38±0.46 GPa for (Cu,Ni)3Sn, respectively. Besides, in-situ nano-compression tests have been conducted on IMCs micro-cantilevers, the fracture strength turns out to be 2.46 GPa. And also, the ultimate tensile stress was calculated to be 2.3±0.7 GPa from in-situ micro-bending tests, which is not sensitive with the microstructural change of IMCs after dwelling at 290 °C.