In tracing the history of the TIROS meteorological satellite system, this dissertation details the convergence of two communities: the DOD space scientists who established US capability to launch and operate these remote sensing systems and the US Weather Bureau meteorologists who would be the managers and users of satellite data. Between 1946 and 1964, these persons participated in successive coalitions. These coalitions were necessary in part because satellite systems were too big—geographically, fiscally, and technically—to be developed and operated within a single institution. Thus, TIROS technologies and people trace their roots to several research centers—institutions that the USWB and later NASA attempted to coordinate for US R&D. The gradual transfer of persons and hardware from the armed services to the non-military NASA sheds light on the US’s evolution as a Cold War global power, shaped from the “top-down” (by the executive and legislative branches) as well as the “bottom-up” (by military and non-military scientific communities). Through these successive coalitions, actor terms centered on “basic science” or the circulation of atmospheric data were used to help define bureaucratic places (the Upper Atmospheric Rocket Research Panel, International Geophysical Year, NASA, and the World Weather Watch) in which basic research would be supported by sustained and collaboration could take place with international partners.

A compreensão da circulação da água em aquíferos requer o levantamento de suas características intrínsecas relacionados à hidrogeologia e às variáveis do ciclo hidrológico. Embora a interface entre as formações geológicas do Sistema Aquífero Guarani (SAG) venha sendo mapeada para verificar a susceptibilidade à explotação e contaminação, faz-se necessário conhecer a heterogeneidade estratigráfica em suas áreas de afloramento. Este estudo visa investigar as propriedades hidrogeológicas usando técnicas geofísicas e modelar numericamente o escoamento subterrâneo em área de afloramento do SAG. Foram utilizados o Ground Penetratring Radar com antena de 200MHz, a sondagem elétrica vertical com arranjo Schlumberger e o imageamento elétrico com arranjo dipolo-dipolo. A interface usada para a modelagem numérica por elementos finitos foi o Simulador de Processos em Aquíferos (SPA). As técnicas geofísicas contribuíram para o modelo numérico com a definição de duas regiões com diferentes condutividades hidráulicas, sendo a maior condutividade próxima à área de descarga. Também foi possível definir uma condição de contorno de fluxo não-nulo pela interpretação dos imageamentos elétricos. Um longo período de 14 anos hidrológicos para uma área com intensa mudança de uso do solo e registro de crise hídrica foi bem simulado pelo modelo numérico apresentando coeficientes de Kling-Gupta não paramétrico (KGENP) para os poços entre 0,52 (P8) e 0,89 (P16) e para vazão de base entre 0,66 (EF-SMF) e 0,93 (CP2). A análise das incertezas e heterogeneidade espaçotemporal da recarga podem contribuir para este trabalho e melhorar o balanço hídrico da área de afloramento do SAG. / Groundwater flux comprehension depends on knowledge of hydrogeological parameters and the water cycle, specially the recharge process. Although geological interfaces of the Guarani Aquifer System have been mapping to verify exploitation and contamination susceptibility, stratigraphy heterogeneity of the outcrop areas are not thoroughly known. The aims of this study are hydrogeological characterization from geophysical techniques and groundwater flux numerical modelling. Ground Penetrating Radar with a 200 MHz antenna, vertical electrical sounding with Schlumberger array and electrical resistivity tomography with dipole-dipole array were used. Also, a finite element model was applied to groundwater flux analysis. Geophysical techniques helped to define two hydraulic conductivity regions and a specified flux boundary condition. A 14-year-long groundwater flux model for an area under intense land use changes and water shortage scenario was well simulated. The non-parametric Kling-Gupta (KGENP) coefficient for the groundwater level varied between 0.52 (P8) and 0.89 (P16); and the KGENP calculated with the baseflow values ranged between 0.66 (EF-SMF) and 0.93 (CP2). More studies are suggested to scientific improvement related to the uncertainty and spatiotemporal heterogeneity recharge of outcrop zones of the Guarani Aquifer System to a better water balance understanding.

En els darrers quinze anys la velocitat de bit dels sistemes de comunicació ionosfèrica s'ha incrementat significativament, passant dels 75 bps als 14400 bps en un ample de banda de 3 KHz. Les millores experimentades en el modelatge i simulació de canal, el desenvolupament dels sistemes ALE i l'aplicació de tècniques digitals (software radio, modulacions de banda ampla, etc.) són, entre altres, alguns dels motius que han permès aquest increment en les prestacions dels equips, fent-los aptes per comunicacions de llarga distància amb requeriments de velocitat de bit moderada.En particular, la propagació ionosfèrica és una tècnica especialment interessant per enllaços des de l'Antàrtida, on la comunicació amb satèl·lits geostacionaris no és sempre possible.El Departament de Comunicacions i Teoria del Senyal de l'Escola d'Enginyeria La Salle (Universitat Ramon Llull) està involucrat, juntament amb l'Observatori de L'Ebre, en un projecte de recerca que té per objectiu l'estudi de l'enllaç ionosfèric que s'estableix entre la Base Antàrtica Espanyola i Roquetes. L'enllaç, que té una longitud de més de 12700 quilòmetres, ha de servir per transmetre les dades procedents d'un sensor geomagnètic situat a la Base, cap a l'Observatori.Aquesta tesi estudia diversos aspectes d'aquest projecte, principalment pel que fa a la caracterització de canal i al disseny de la capa física adaptada per transmissió eficient de dades.En referència a la caracterització de canal es mostren els resultats d'una campanya de 60 dies de sondeig duta a terme durant l'estiu austral 2006/07 en la que s'han realitzat proves de banda estreta i banda ampla per tal d'obtenir, entre altres, la disponibilitat de l'enllaç, relació senyal a soroll i dispersió temporal i freqüencial.En l'àmbit de la transmissió de dades es proposa, justifica i verifica experimentalment una part d'una capa física basada en espectre eixamplat per seqüència directa especialment adaptada a enllaços a llocs remots: (i) Sense atribució de freqüències; (ii) Amb potència de transmissió relativament baixa; (iii) Infraestructura de radiació limitada. La proposta contempla el funcionament amb relacions SNR negatives, dispersió temporal i freqüencial moderada, robustesa a la interferència i baixa densitat espectral de potència. / En los últimos quince años la velocidad de bit de los sistemas de comunicación ionosférica se ha incrementado significativamente, pasando de los 75 bps a los 14400 bps en un ancho de banda de 3 kHz. Las mejoras experimentadas en el modelado y simulación del canal, el desarrollo de los sistemas ALE y la aplicación de técnicas digitales (software radio, modulaciones de banda ancha, etc.) son, entre otros, algunos de los motivos que han permitido este incremento en las prestaciones de los equipos, haciéndolos aptos para comunicaciones de larga distancia con requerimientos de velocidad de bit moderada.En particular, la propagación ionosférica es una técnica especialmente interesante para enlaces desde la Antártida, donde la comunicación con satélites geostacionarios no es siempre posible.El Departamento de Comunicaciones y Teoría de la Señal de la Escuela de Ingeniería La Salle (Universidad Ramon Llull) está involucrado, junto al Observatorio del Ebro, en un proyecto de investigación que tiene por objetivo el estudio del enlace ionosférico que se establece entre la Base Antártica Española y Roquetes. El enlace, que tiene una longitud de más de 12700 kilómetros, debe servir para transmitir los datos procedentes de un sensor geomagnético situado en la Base, hacia el Observatorio.Esta tesis estudia varios aspectos de este proyecto, principalmente por lo que respecta a la caracterización del canal y al diseño de la capa física adaptada para la transmisión eficiente de datos.En lo referente a la caracterización del canal se muestran los resultados de una campaña de 60 días de sondeo llevada a cabo durante el verano austral 2006/07 en la que se han realizado pruebas de banda estrecha y banda ancha para obtener, entre otros, la disponibilidad del enlace, relación señal a ruido y dispersión temporal y frecuencial.En el ámbito de la transmisión de datos se propone, justifica y verifica experimentalmente una parte de una capa física basada en espectro ensanchado por secuencia directa especialmente adaptada a enlaces a lugares remotos: (i) Sin atribución de frecuencias; (ii) Con potencia de transmisión relativamente baja; (iii) Infraestructura de radiación limitada. La propuesta contempla el funcionamiento con relaciones SNR negativas, dispersión temporal y frecuencial moderada, robustez a la interferencia y baja densidad espectral de potencia. / In the last fifteen years the data rate of the ionospheric communication systems has increased significantly from 75 bps to 14400 bps in a 3 KHz bandwidth. The improvements achieved in the field of channel modeling and simulation, ALE systems and the application of digital techniques (e.g. software radio, wideband modulations, etc.) have permitted the design of new equipment with better performance. As a result, the establishment of low power, very long radio links with moderate data rate has become feasible.In special, the ionospheric propagation technique is very appropriate for radio links from the Antarctica, where the communication to geostationary satellites is not always possible.The Communications and Signal Theory Department of La Salle School of Engineering (Universitat Ramon Llull) and the Observatori de l'Ebre are involved in a research project dealing with the study of an ionospheric radio link between the Spanish Antarctic Base and Roquetes. The link is 12700 Km. long and is going to be used to transmit the low data rate information from a geomagnetic sensor installed in the Spanish Antarctic Base.This thesis has been carried out in the framework of this project, and its goals are related to the channel characterization and the partial design of a physical layer adapted to an efficient transmission of information over that link.Regarding the channel characterization, the results of a 60-days sounding survey corresponding to the 2006/07 southern summer are shown. These results include, among others, link availability, signal to noise ratio and delay and Doppler spread.In the field of data transmission a new physical layer is proposed and experimentally verified, on the basis of the channel measurements and adapted to the requirements and the special conditions in the Antarctica. This physical layer is based on direct sequence spread spectrum and his main characteristics are: (i) Intended for an HF communication without a fixed frequency allocation; (ii) Low emitted power; (iii) Simple radiation infrastructure. The proposal takes into account the operation with negative signal to noise ratios, moderate delay and Doppler spreads, robustness against interference and low power spectral density.

This item contains the agenda, minutes, and attachments for the Faculty Senate meeting on this date. There may be additional materials from the meeting available at the Faculty Center. / Minutes originally posted on Dec. 3rd, 2013; correction made to minutes and reposted on Feb. 3rd, 2014.

Originally developed in the 1970s for the optimal control of systems governed by partial differential equations, the adjoint method has found several successful applications, e.g. in meteorology with large-scale 3D or 4D atmospheric data assimilation schemes, for carbon cycle data assimilation in biogeochemistry and climate research, or in oceanographic modelling with efficient adjoint codes of ocean general circulation models.<p><p>Despite the variety of applications in these research fields, adjoint methods have only very recently drawn attention from the ocean acoustics community. In ocean acoustic tomography and geoacoustic inversion, where the inverse problem is to recover unknown acoustic properties of the water column and the seabed from acoustic transmission data, the solution approaches are typically based on travel time inversion or standard matched-field processing in combination with metaheuristics for global optimization. <p><p>In order to complement the adjoint schemes already in use in meteorology and oceanography with an ocean acoustic component, this thesis is concerned with the development of the adjoint of a full-field acoustic propagation model for shallow water environments. <p><p>In view of the increasing importance of global ocean observing systems such as the European Seas Observatory Network, the Arctic Ocean Observing System and Maritime Rapid Environmental Assessment (MREA) systems for defence and security applications, the adjoint of an ocean acoustic propagation model can become an integral part of a coupled oceanographic and acoustic data assimilation scheme in the future. <p><p>Given the acoustic pressure field measured on a vertical hydrophone array and a modelled replica field that is calculated for a specific parametrization of the environment, the developed adjoint model backpropagates the mismatch (residual) between the measured and predicted field from the receiver array towards the source.<p><p>The backpropagated error field is then converted into an estimate of the exact gradient of the objective function with respect to any of the relevant physical parameters of the environment including the sound speed structure in the water column and densities, compressional/shear sound speeds, and attenuations of the sediment layers and the sub-bottom halfspace. The resulting environmental gradients can be used in combination with gradient descent methods such as conjugate gradient, or Newton-type optimization methods tolocate the error surface minimum via a series of iterations. This is particularly attractive for monitoring slowly varying environments, where the gradient information can be used to track the environmental parameters continuously over time and space.<p><p>In shallow water environments, where an accurate treatment of the acoustic interaction with the bottom is of outmost importance for a correct prediction of the sound field, and field data are often recorded on non-fully populated arrays, there is an inherent need for observation over a broad range of frequencies. For this purpose, the adjoint-based approach is generalized for a joint optimization across multiple frequencies and special attention is devoted to regularization methods that incorporate additional information about the desired solution in order to stabilize the optimization process.<p><p>Starting with an analytical formulation of the multiple-frequency adjoint approach for parabolic-type approximations, the adjoint method is progressively tailored in the course of the thesis towards a realistic wide-angle parabolic equation propagation model and the treatment of fully nonlocal impedance boundary conditions. A semi-automatic adjoint generation via modular graph approach enables the direct inversion of both the geoacoustic parameters embedded in the discrete nonlocal boundary condition and the acoustic properties of the water column. Several case studies based on environmental data obtained in Mediterranean shallow waters are used in the thesis to assess the capabilities of adjoint-based acoustic inversion for different experimental configurations, particularly taking into account sparse array geometries and partial depth coverage of the water column. The numerical implementation of the approach is found to be robust, provided that the initial guesses are not too far from the desired solution, and accurate, and converges in a small number of iterations. During the multi-frequency optimization process, the evolution of the control parameters displays a parameter hierarchy which clearly relates to the relative sensitivity of the acoustic pressure field to the physical parameters. <p><p>The actual validation of the adjoint-generated environmental gradients for acoustic monitoring of a shallow water environment is based on acoustic and oceanographic data from the Yellow Shark '94 and the MREA '07 sea trials, conducted in the Tyrrhenian Sea, south of the island of Elba.<p> <p>Starting from an initial guess of the environmental control parameters, either obtained through acoustic inversion with global search or supported by archival in-situ data, the adjoint method provides an efficient means to adjust local changes with a couple of iterations and monitor the environmental properties over a series of inversions. <p><p>In this thesis the adjoint-based approach is used, e.g. to fine-tune up to eight bottom geoacoustic parameters of a shallow-water environment and to track the time-varying sound speed profile in the water column. <p><p>In the same way the approach can be extended to track the spatial water column and bottom structure using a mobile network of sparse arrays.<p><p>Work is currently being focused on the inclusion of the adjoint approach into hybrid optimization schemes or ensemble predictions, as an essential building block in a combined ocean acoustic data assimilation framework and the subsequent validation of the acoustic monitoring capabilities with long-term experimental data in shallow water environments. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Abstract This thesis concentrates on the design and evaluation of spatial user multiplexing methods via linear transmit-receive processing for wireless cellular multi-user multiple-input multiple-output (MIMO) communication systems operating in the time-division duplexing (TDD) mode. The main focus is on the acquisition of effective channel state information (CSI) that facilitates decentralized processing so that the network nodes – base stations (BS) and user terminals (UT), each employing an arbitrary number of antenna elements – are able to locally participate in the network adaptation. The proposed methods rely on the uplink-downlink channel reciprocity and spatially precoded over-the-air pilot signaling. Considering (single-cell) multi-user MIMO systems, coordinated zero-forcing transmit-receive processing schemes for the uplink (UL) are proposed. The BS computes the transmission parameters in a centralized manner and employs downlink (DL) pilot signals to convey the information of the beamformers to be used by the UTs. When coexisting with the DL zero-forcing, the precoded DL demodulation pilots can be reused for UL beam allocation, and the precoded UL demodulation pilots are reused in turn for partial channel sounding (CS). As a result, only the precoded pilot symbols are needed in both UL and DL. Moreover, a concept for reducing the number of the required orthogonal UL CS pilot resources is presented. Based on their DL channel knowledge, the multi-antenna UTs form fewer pilot beams by spatial precoding than conventionally needed when transmitting antenna-specific pilots. In the context of DL zero-forcing, when taking into account the CSI estimation error at the BS, the overhead reduction turns out to improve robustness and increase the average system capacity. Considering multi-cell multi-user MIMO systems, decentralized coordinated DL beamforming strategies based on weighted sum rate (WSR) maximization are proposed. An optimization framework where the WSR maximization is carried out via weighted sum mean-squared-error minimization is utilized, and the approach is generalized by employing antenna-specific transmit power constraints. The iterative processing consists of optimization steps that are run locally by the BSs. In one novel strategy, the coordinating cells update their transmit precoders and receivers one cell at a time, which guarantees monotonic convergence of the network-wide problem. The strategy employs separate uplink CS and busy burst pilot signaling to reveal the effective channels of the UTs to the neighboring BSs. In another novel strategy, the monotonic convergence is sacrificed to devise a faster scheme where the BSs are allowed to optimize their variables in parallel based on just the CS responses and additional low-rate backhaul information exchange. The numerical results demonstrate that WSR maximization has the desirable property that spatial user scheduling is carried out implicitly. Finally, methods for UL CS overhead reduction are presented, and the effect of CSI uncertainty is addressed. / Tiivistelmä Tämä väitöskirja keskittyy lineaarisella lähetys- ja vastaanottoprosessoinnilla toteutettavien tilajakomonikäyttömenetelmien suunnitteluun ja arviointiin langattomissa moniantennisissa solukkoverkoissa, jotka hyödyntävät aikajakodupleksointia (TDD). Erityisesti tarkastellaan efektiivisen kanavatiedon hankintaa, joka mahdollistaa hajautetun prosessoinnin siten että verkkoelementit – tukiasemat ja terminaalit, jotka kukin hyödyntävät useaa antennielementtiä – voivat osallistua paikallisesti verkon adaptaatioon. Esitetyt menetelmät perustuvat ylä- ja alalinkin kanavien resiprookkisuuteen ja tilatasossa esikoodattuun opetus- eli pilottisignalointiin ilmarajapinnan yli. Yksisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään ylälinkin koordinoituja nollaanpakottavia lähetys- ja vastaanottomenetelmiä. Tukiasema laskee lähetysparametrit keskitetysti ja käyttää pilottisignaaleja kertomaan millaista lähetyskeilanmuodostusta terminaalien tulee käyttää. Alalinkin nollaanpakotuksen yhteydessä esikoodattuja demodulaatiopilotteja voidaan uudelleenkäyttää ylälinkin lähetyskeilojen allokointiin, ja esikoodattuja ylälinkin demodulaatiopilotteja uudelleenkäytetään puolestaan osittaiseen kanavan luotaukseen (sounding). Näin ollen molempiin suuntiin tarvitaan vain esikoodatut pilotit. Lisäksi työssä esitetään menetelmä ylälinkin luotauspilottiresurssitarpeen vähentämiseksi. Kanavatietoon perustuen moniantenniset terminaalit muodostavat tilatasossa esikoodattuja pilottilähetyskeiloja, joita tarvitaan vähemmän kuin perinteisiä antennikohtaisia pilotteja. Kun otetaan huomioon kanavanestimointivirhe tukiasemassa, resurssiensäästömenetelmä parantaa häiriösietoisuutta ja nostaa järjestelmän keskimääräistä kapasiteettia alalinkin nollaanpakotuksen yhteydessä. Monisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään hajautettuja koordinoituja alalinkin keilanmuodostusstrategioita, jotka perustuvat painotetun summadatanopeuden (WSR) maksimointiin. Valitussa optimointikehyksessä WSR:n maksimointi toteutetaan painotetun summaneliövirheen minimoinnin kautta, ja työssä menettelytapa yleistetään antennikohtaisten lähetystehorajoitusten tapaukseen. Iteratiivinen prosessointi koostuu optimointiaskelista, jotka tukiasemat paikallisesti suorittavat. Yhdessä esitetyssä strategiassa yhteistoiminnalliset solut päivittävät lähettimensä ja vastaanottimensa yksi solu kerrallaan, mikä takaa verkonlaajuisen ongelmanratkaisun monotonisen konvergenssin. Tämä strategia käyttää erillisiä ylälinkin luotaussignaaleja sekä varattu-signaaleja ilmaistakseen terminaalien efektiiviset kanavat naapuritukiasemille. Toisessa strategiassa monotoninen konvergenssi uhrataan ja kehitetään nopeammin adaptoituva menetelmä, jossa tukiasemat saavat optimoida muuttujansa rinnakkain, perustuen vain luotaussignaaleihin ja tukiasemien väliseen informaationvaihtoon. Numeeriset tulokset osoittavat, että WSR:n maksimointi toteuttaa aktiivisten käyttäjien valinnan tilatasossa implisiittisesti. Lopuksi esitetään menetelmiä luotauspilottiresurssitarpeen vähentämiseksi ja käsitellään kanavatiedon epävarmuuden vaikutusta.

Polygonal cryogenic structures cannot be investigated with conventional methods as they could be harmed during measurement. A real3D GPR and ERT non-destructive surveys were used to examine and prove applicability for topsoil covered ice-wedge pseudomorphs and coarse-grained sorted polygons (patterned ground). A list of processing tools and algorithm suitable for such environments was created and tested. The benefits of 3D measurements are illustrated on horizontal slices and pseudo3D visualisation of 3D Cube. Basic morphometry characteristics of both forms were collected. Abilities of geophysical imaging for advanced shape characterisations are discussed, too. The low-frequency measurements gave better results at both sites. Pseudomorphs, 2 wide and up to 6,5 long, were found penetrating depth bigger than 3,5 . Sorted polygons, 2,5 wide in diameter, were depicted locked by stony ring of width around 1 . Sorting depth extends up to 0,54 depth for sure, perhaps more.

Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of snow, (2) modeling an optical Bragg resonator, and (3) modeling the MIMO wireless channel. First, complex snow media is analyzed with a hybrid FDTD/radiative transfer model. FDTD is used to compute phase matrices and extinction coefficients required for radiative transfer. Comparison with exact analytical methods proves the validity of the FDTD method for modest domain sizes ([5λ^3]) and number of Monte Carlo realizations (32). The method is used to illustrate a penetrating sphere model, which is not possible with existing analysis techniques. Backscatter from the resulting model is about 3 times higher than that of existing dense-medium theories, underlying the importance of exact characterization of the media. Second, a hybrid FD/FDTD/S-parameter analysis is developed to model a large (10^4 section) optical Bragg resonator: a simple FD method computes propagation constants and field profiles, FDTD analysis provides reflection and transmission coefficients for the single section, and S-parameter analysis combines the sections to obtain the complete device response. A detailed study on error suggests that the method provides better than 2% accuracy in reflection and transmission response. Third, a hybrid electromagnetic/SVA model is developed to study the indoor MIMO wireless channel. A MIMO measurement platform is discussed for simultaneous probing of up to 16 transmit and receive antennas, which was required to assess the validity of later modeling. FDTD or MOM antenna analysis coupled with the SVA model gives capacity predictions which match measured data. The model is used to explore the impact of antenna spacing, directivity, and polarization on channel capacity. Closely spaced antennas lead to an approximate halving of receive power. Directivity effectively doubles receive power for aligned transmit and receive. Dual polarization increases system capacity anywhere from 10% to 70%, depending on the spacing of elements and the amount of multipath richness. This analysis of MIMO systems underlines the need for models that describe both multipath richness and average receive power.

La integración de tecnologías de ulta-wideband, radio-cognitiva y MIMO representa una herramienta podersoa para mejorar la eficiencia espectral de los sistemas de comunicación inalámbricos. En esta dirección, nuevas estrategias para el modelado de canales MIMO y su caracterización se hacen necesarias si se desea investigar cómo la frecuencia central y el acho de banda afectan el desempeño de los sistemas MIMO. Investigaciones preliminares han enfocado menos atención en cómo estos parámetros afectan las características del canal MIMO. Se presenta una caracterización del canal MIMO en función de la frecuencia, abondándose puntos de vista experimentales y teóricos. Los problemas indicados tratan cinco áreas principales: medidas, post-procesado de datos, generación sintética del canal, estadística multivariable para datos y modelado del canal. Se ha diseñado y validado un sistema de medida basado en un analizador vectorial de redes y se han ejecutado medidas entre 2 y 12 GHz en condiciones estáticas, tanto en línea de vista como no línea de vista. Se ha propuesto y validado un procedimiento confiable para post-procesado, generación sintética de canal y análisis experimental basado en medidas en el dominio de frecuencia. El procedimiento experimental se ha focalizado en matrices de transferencia del canal para casos no selectivos en frecuencia, estimándose además las matrices complejas de covarianza, aplicándose la factorización de Cholesky sobre ls CCM y obteniéndose finalmente matrices de coloreado del sistema. Se presenta un procedimiento de corrección para generación sintética del canal aplicado a casos MIMO de grandes dimensiones y cuando la CCM es indefinida. Este CP permite la factorización de Cholesky y de dichas CCM. Las características multivariables de los datos experimentales han sido investigadas, realizándose un test de normalidad compleja multivariable. / García Ariza, AP. (2009). Modelling and experimental analysis of frequency dependent MIMO channels [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6563

The increased temperatures in the Arctic accelerate the loss of land based ice stored in glaciers. The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere and holds ~10% of all the freshwater on Earth, equivalent to ~7 metres of global sea level rise. A few decades ago, the mass balance of the Greenland Ice Sheet was poorly known and assumed to have little impact on global sea level rise. The development of regional climate models and remote sensing of the ice sheet during the past decade have revealed a significant mass loss. To monitor how the Greenland Ice Sheet will affect sea levels in the future requires understanding the physical processes that govern its mass balance and movement. In the southeastern and central western regions, mass loss is dominated by the dynamic behaviour of ice streams calving into the ocean. Changes in surface mass balance dominate mass loss from the Greenland Ice Sheet in the central northern, southwestern and northeastern regions. Little is known about what the hydrological system looks like beneath the ice sheet; how well the hydrological system is developed decides the water’s impact on ice movement. In this thesis, I have focused on radar sounding measurements to map the subglacial topography in detail for a land-terminating section of the western Greenland Ice Sheet. This knowledge is a critical prerequisite for any subglacial hydrological modelling. Using the high-resolution ice thickness and bed topography data, I have made the following specific studies: First, I have analysed the geological setting and glaciological history of the region by comparing proglacial and subglacial spectral roughness. Second, I have analysed the subglacial water drainage routing and revealed a potential for subglacial water piracy between adjacent subglacial water catchments with changes in the subglacial water pressure regime. Finally, I have looked in more detail into englacial features that are commonly observed in radar sounding data from western Greenland. In all, the thesis highlights the need not only for accurate high-resolution subglacial digital elevation models, but also for regionally optimised interpolation when conducting detailed hydrological studies of the Greenland Ice Sheet. / De ökade temperaturerna i Arktis påskyndar förlusten av landbaserad is lagrad i glaciärer och permafrost. Grönlands inlandsis är den största ismassan på norra halvklotet och lagrar ca 10% av allt sötvatten på jorden, vilket motsvarar ca 7 meter global havsnivåhöjning. För ett par decennier sedan var inlandsisens massbalans dåligt känd och antogs ha liten inverkan på dagens havsnivåhöjning. Utvecklingen av regionala klimatmodeller och satellitbaserad fjärranalys av inlandsisen har under de senaste decenniet påvisat en betydande massförlust. För att förutse vilken inverkan inlandsisen har på framtida havsnivåhöjningar krävs en förståelse för de fysikaliska processerna som styr dess massbalans och isrörelse. I de sydöstra och centrala västra delarna av inlandsisen domineras massförlusten av dynamiska processer i isströmmar som kalvar ut i havet. Massförlusten i de centrala norra, sydvästra och nordöstra delarna domineras av isytans massbalans. Ytterst lite är känt om hur det hydrologiska systemet ser ut under inlandsisen; hur väl det hydrologiska systemet är utvecklat avgör vattnets påverkan på isrörelsen. I denna doktorsavhandling har jag använt markbaserade radarmätningar för att kartlägga den subglaciala topografin för en del av den västra landbaserade inlandsisen. Denna kunskap är en viktig förutsättning för att kunna modellera den subglaciala hydrologin. Med hjälp av rumsligt högupplöst data över istjockleken och bottentopografin har jag gjort följande specifika studier: Först har jag analyserat de geologiska och glaciologiska förhållandena i regionen genom att jämföra proglacial och subglacial spektralanalys av terrängens ytojämnheter. Sedan har jag analyserat den subglaciala vattenavrinningen och påvisat en potential för att avrinningsområdena kan ändras beroende på vattentryckförhållandena på botten. Slutligen har jag tittat mer i detalj på englaciala radarstrukturer som ofta observerats i radardata från västra Grönland. Sammanfattningsvis belyser avhandlingen behovet av inte bara noggranna rumsligt högupplösta subglaciala digitala höjdmodeller, utan även regionalt optimerad interpolering när detaljerade hydrologiska studier ska utföras på Grönlands inlandsis.