Stationary wave theory elucidates the dynamics of the time mean zonally asymmetric component of the atmospheric circulation and separates it from the dynamics of the zonal mean climatological flow. This thesis focuses on the dynamics of stationary wave nonlinearity and its applications in stationary wave modelling and the stationary wave response to climate change. Stationary wave nonlinearity describes the self-interaction of stationary waves and is important in maintaining the observed zonally asymmetric atmospheric general circulation. Stationary wave nonlinearity is examined in quasi-geostrophic barotropic dynamics in both the presence and absence of transient waves. Stationary wave nonlinearity is shown to account for most of the difference between the linear and full nonlinear stationary waves, particularly if the zonal-mean flow adjustment to the stationary waves is taken into account. Wave activity analysis shows that stationary wave nonlinearity in this setting is associated with Rossby wave critical layer reflection. A time-integration type nonlinear stationary wave modelling technique is tested in this simple barotropic setting and is shown to be able to predict stationary wave nonlinearity and capture the basic features of the full nonlinear stationary wave. A baroclinic nonlinear stationary wave model is then developed using this technique and is applied to the problem of the stationary wave response to climate change. Previous stationary wave modelling has largely focused on the tropospheric circulation, but the stationary wave field extends into the stratosphere and plays an important dynamical role there. This stationary wave model is able to represent the stratospheric stationary wave field and is used to analyze the Northern Hemisphere stationary wave response to climate change simulated by the Canadian Middle Atmosphere Model (CMAM). In the CMAM simulation changes to the zonal mean basic state alone can explain much of the stationary wave response, which is largely controlled by changes of the zonal mean circulation in the Northern Hemisphere subtropical upper troposphere. However, details of the stratospheric wave driving response are also sensitive to other aspects of the zonal-mean response and to the heating response. Many climate change related effects appear to contribute robustly to an increased wave activity flux into the stratosphere.

Chemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding contaminant fate and transport. This work explored the effects of soil structure (i.e. layers, lenses) on linked geochemical, hydrological, and microbiological processes under changing hydrologic conditions (e.g. rainfall, introduction of groundwater, and fluctuating water table heights). A homogenized medium-grained sand, homogenized organic-rich loam and a sand-over-loam layered column were constructed for the first series of experiments. The second series of experiments employed two soil columns with lenses that were packed identically with sterilized and untreated sediments. Each consisted of two lenses of organic-rich loam in a medium-grained sand matrix. Lenses were located at different vertical depths and were horizontally offset. In-situ collocated probes collected soil hydrologic and chemical data. In the layered column, enhanced biogeochemical cycling was observed over the texturally homogeneous soil columns. Enumerations of Fe(III) and SO42- reducing microorganisms also show 1-2 orders of magnitude greater community numbers in the layered column. The greatest concentrations of aqueous FeS clusters (FeSaq) were observed in close proximity to the soil interface. To our knowledge, this was the first documentation of FeSaq in partially saturated sediments. Mineral and soil aggregate composite layers were also most abundant near the soil layer interface; the presence of which, likely contributed to an order of magnitude decrease of hydraulic conductivity. In the live lens column, Fe-oxide bands formed at the fringes of the lenses that retarded water flow rates by an order of magnitude compared to the sterilized column. Microbial activity also produced insoluble gases and that led to the creation of a separate gas phase that reduced hydraulic conductivity. This limited the interaction between groundwater with soil-pore waters that led to the formation of geochemically distinct water masses in relatively close proximity to one another. No such changes were observed in the sterilized column. When compared to homogenous columns, the presence of soil heterogeneities altered biogeochemical and hydrologic processes considerably which highlights the need to consider soil heterogeneity in contaminant fate and transport models. These findings suggest that quantifying coupled hydrologic-biogeochemical processes occurring at small scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale.

La mayoría de las estructuras de hormigón armado se someten a solicitaciones combinadas de esfuerzos axiles, flexión, cortante y torsión. La fisuración del hormigón, plastificación de las armaduras y otros efectos no-lineales hacen que las secciones transversales de estos elementos presenten un comportamiento anisótropo que deriva en el acoplamiento de los esfuerzos normales y tangenciales. Es decir, esfuerzos normales o momentos flectores pueden producir deformaciones de corte y vice versa. Aunque en algunas ocaciones, esta interacción es considerada de forma simplificada en el dimensionamiento de estructuras, hasta el momento no se ha realizado un análisis profundo de los efectos acoplados en secciones de forma arbitraria bajo cargas 3D generales utilizando modelos de fibras.El objetivo principal de esta tesis es generalizar el análisis de secciones de hormigón armado mediante fibras, de forma que se pueda reproducir la res-puesta no-lineal acoplada frente a esfuerzos normales y tangenciales bajo solicitaciones tridimensionales generales. De igual forma, se pretende obtener, para los esfuerzos cortantes y torsión, la misma capacidad de representación de geometrías y combinación de materiales que ofrecen los modelos de fibras para esfuerzos de flexo-compresión.La primera problemática estriba en representar adecuadamente la cinemática de la sección transversal. Con la excepción de las deformaciones normales contenidas en el plano de la sección, no existe una teoría cinemática que a priori pueda dar la distribución del resto de deformaciones o tensiones en la sección, sin dejar de satisfacer las condiciones de equilibrio interno o continuidad entre las fibras que componen la misma.Por otra parte, para materiales anisótropos, como el hormigón fisurado, en general todos los esfuerzos internos pueden estar acoplados. Además, es preciso considerar la distorsión de la sección transversal para satisfacer el equilibrio entre fibras.El problema se aborda de forma general, considerando una sección de forma y materiales cualesquiera. Se parte del problema diferencial de equilibrio de un sólido con el que se ha podido deducir un sistema de equilibrio entre fibras (equilibrio a nivel sección). Se puede demostrar que éste es complementario al problema estándar de vigas. El sistema complementario permite recuperar información tridimensional que normalmente se pierde al resolver un problema de vigas.Posteriormente, se propone una solución interna del problema complementario, en la que el alabeo y la distorsión de la sección quedan expresados como una función de las deformaciones generalizadas de una viga: deformaciones axil y cortantes, curvaturas de flexión y torsión. No son necesarios grados de libertad adicionales a nivel estructura ni hipótesis a-priori sobre la forma de los campos de deformación o tensión interna.A partir de la formulación teórica, se desarrolla un modelo de elementos finitos plano de la sección transversal. El modelo está preparado para servir como respuesta constitutiva de cualquier tipo de elemento viga en sus puntos de integración. %Se evita así la necesidad de realizar un modelo de elementos sólidos de toda la barra para estudiar la respuesta frente a una combinación general de esfuerzos normales y tangenciales.Se implementan una serie de modelos constitutivos para distintos materiales. En particular, se implementa un modelo constitutivo triaxial para hormigón fisurado, considerando la anisotropía inducida por la fisuración e incluyendo la superficie de rotura según un criterio multiaxial.La formulación seccional es validada mediante varios casos de estudio teóricos y experimentales. La respuesta no-lineal acoplada bajo diversas combinaciones de esfuerzos normales y tangenciales es reproducida con precisión, lo cual queda patente tanto en las curvas esfuerzo-deformación obtenidas como en las matrices de rigidez seccionales.Finalmente, se recopilan las conclusiones derivadas de la presente investigación y seofren recomendaciones para futuros trabajos. / Most RC structures are subjected to combined normal and tangential forces, such as bending, axial load, shear and torsion. Concrete cracking, steel yielding and other material nonlinearities produce an anisotropic sectional response that results in a coupling between the effects of normal and shear forces, i.e. normal force or bending moments may produce shear strains and vice versa. Although this interaction is sometimes taken into account, in a simplified manner, in the design of RC structures, a deep analysis of the coupling effects of RC sections using fiber models has not yet been made for arbitrary shape sections under general 3D loading.The main objective of this thesis is to generalize the fiber-like sectional analysis of reinforced concrete elements, to make it capable of considering the coupled non-linear response under tangential and normal internal forces, from a general 3D loading.Similarly, it is desired to obtain, for torque and shear forces, the same capacity and versatility in reproducing complex geometry and materials combination that fiber-like sectional representations offers for bending and stretching.The first problematic lies in finding a proper representation of the section's kinematics under such general loading. Except for in-plane normal strains, there is no single kinematical theory capable of a-priori representing the correct distribution of the others strains or stresses satisfying, at the same time, inter-fiber equilibrium and continuity. On the other hand, for rather anisotropic materials, such as cracked concrete, all internal forces are, in general, coupled. It is also required that distortion is allowed for the section's kinematics in order to guarantee satisfaction of internal equilibrium.The problem is dealt in a general form considering arbitrary shaped sections and any material behaviour. Starting from the differential equilibrium of a solid, an inter-fiber equilibrium system (equilibrium at the sectional level) was deduced. This system, which is complementary to the standard equilibrium problem of a beam-column, allows to recuperate information of the three-dimensional problem that is generally lost when solving a beam problem.Further, a solution of the equilibrium at the sectional level is proposed in which the section's warping and distortion are posed as a function of the generalized beam-column strains (axial and shear strains, bending and torsion curvatures). No additional degrees of freedom are required at the structural level nor a-priori hypotheses on the distribution of the internal strains or stresses.After the theoretical formulation, a planar finite element model for cross-sectional analysis is developed. The model can be used as a constitutive law for general beam column elements at their integration points.A series of constitutive models have been implemented for several materials. In particular, a triaxial constitutive model for cracked concrete is implemented considering crackinduced anisotropy and a multiaxial failure criterion.The sectional formulation is validated by means of various theoretical and experimental case studies. Non-linear coupled response under normal and tangential internal forces is reproduced with accuracy, as can be seen both in the predicted internal force-strain curves and in the sectional stiffness matrixes.Finally, the conclusions drawn from the current research are summarized andrecomendations for future works are given.

La técnica de las ondas de Lamb acopladas por aire representa un importante avance en el área de los Ensayos No Destructivos (END) de materiales laminares.Sin embargo la compleja naturaleza de las vibraciones mecánicas encontradas en acústica, hacen que el análisis y el estudio de esta área del conocimiento sea un tema muy complejo. De allí que la posibilidad de contar con una herramienta de simulación de software que permita la evaluación y prueba de diferentes configuraciones de excitación y recepción acústica utilizando la flexibilidad de un modelo de computadora sea de una gran utilidad y ayuda.El objetivo de la presente tesis es proveer al área de los END con un software de simulación gratuito: The LAMB Matlab® toolbox basado en el modelo del software libre de la GNU.El software es capaz de simular el comportamiento de sistemas de END basados en ondas de Lamb acopladas por aire en láminas isótropas simples utilizando transductores tipo array.El programa se basa en un arreglo tipo C-scan de un sistema de END y está compuesto por tres bloques principales: 1) Excitación, 2) Propagación y 3) Recepción.La verificación individual del funcionamiento de dichos módulos se presenta a lo largo de la tesis mediante una serie de comparaciones entre simulaciones y datos experimentales provenientes de diferentes pruebas. Por otro lado, la validación del programa completo se llevo a cabo por medio de experimentos en láminas de cobre y aluminio; utilizando un sistema real de END por ondas de Lamb acopladas en aire mediante arrays cóncavos.La influencia negativa en el desempeño general de dicho sistema de END real basado en este tipo de transductores se comprobó efectivamente mediante el simulador desarrollado. Esto se debió fundamentalmente al efecto de directividad de los sensores individuales en los transductores y a la simetría cóncava de los arrays.Para emular este comportamiento la tesis presenta un modelo geométrico bidimensional simple de un filtro espacial, junto a las simulaciones de un nuevo tipo de array plano propuesto.El programa desarrollado comprobó así mismo la naturaleza coherente de los campos acústicos emitidos en aire por las láminas sujetas a vibraciones de Lamb. Esto se realizó mediante la implementación de un conformador de haz simple de suma y demora; constituyéndose así la etapa inicial de procesamiento de señal del bloque de recepción del programa.El objetivo principal del presente trabajo fue contribuir con un modelo operativo de simulación y prueba de nuevos diseños de arrays e implementación de estrategias de procesado de señal útiles en sistemas de END basados en ondas de Lamb acopladas por aire.Finalmente, si bien el objetivo de la calibración del programa no se pudo conseguir; si se logró efectivamente un notable grado de similitud con un sistema de END real. / Air-coupled ultrasonic Lamb waves represent an important advance in Non- Destructive Testing and Evaluation (NDT & NDE) techniques of plate materials and structures. Examples of these advances are the characterization and quality assessment of laminate materials in manufacturing processes, the location of damaged parts in aircrafts and structure monitoring in the aerospace industry.However the rich and complex nature of mechanical vibrations encountered in acoustics make the subject of analysis and study of these systems a very complex task. Therefore a simulation tool that permits the evaluation and testing of different configuration scenarios using the flexibility of a computer model is an invaluable aid and advantage.The objective of this thesis is to provide the field of NDT with free open source software i.e. the LAMB Matlabrtoolbox. The toolbox is capable of simulating the behaviour of Lamb wave based NDE systems for single ideal isotropic laminates using air-coupled ultrasonic arrays. The programme usesa pitch-catch type of a Cscan NDE arrangement and is composed of three integrated sections each individually modelling a feature in the system: 1) Excitation, 2) Propagation, and 3) Reception.For assessment of the individual modules of the toolbox the thesis presents comparisons between each section simulations and the data obtained from different acoustic experiments. The validation of the complete simulator was carried out by evaluation tests on the copper and aluminium plates by use of a real hardware prototype of a Lamb wave based NDE system with aircoupled concave arrays.The negative impact on the performance of the real air-coupled NDE systembased on concave arrays was effectively confirmed by the programme. This was produced by the inherent directivity of the individual sensors as well as their concave arrangement. To emulate this behaviour the thesis introduces a simple two-dimensional geometric model for the inclusion of the spatial filtering effect of the sensors plus a group of simulations for a new proposed air-coupled plane array transducer.The software also verified the spatial coherent nature of the Lamb wave fields emitted by a plate in air. This was demonstrated by the implementation of a delay and sum beamformer to constitute an initial signal processing stage in the reception section.

Capacitive communication using human body as a electrical channel has attracted much attention in the area of personal area networks (PANs) since its introduction by Zimmerman in 1995. The reason being that the personal information and communication appliances are becoming an integral part of our daily lives. The advancement in technology is also helping a great deal in making them interesting,useful and very much affordable. If we interconnect these body-based devices with capacitive communication approach in a manner appropriate to the power, size, cost and functionality, it lessens the burden of supporting a communication channel by existing wired and wireless technologies. More than that, using body as physical communication channel for a PAN device compared to traditional radio transmission seems to have a lot of inherent advantages in terms of power and security etc. But still a lot of feasibility and reliability issues have to be addressed before it is ready for prime time. This promising technology is recently sub-classified into body area networks (BAN) and is currently under discussion in the IEEE 802.15.6 Task Group for addressing the technical requirements to unleash its full potential for BANs. This could play a part in Ericsson's envision of  50 billion connections by 2020. This thesis work is part of the main project to investigate the models, interface and derive requirements on the analog-front-end (AFE) required for the system. Also to suggest a first order model of the AFE that suits this communication system.In this thesis work the human body is modeled along with interfaces and transceiver to reflect the true condition of the system functioning. Various requirements like sensitivity, dynamic range, noise figure and signal-to-noise ratio (SNR) requirements are derived based on the system model. An AFE model based on discrete components is simulated, which was later used for proof of concept. Also a first order AFE model is developed based on the requirements derived. The AFE model is simulated under the assumed interference and noise conditions. The first order requirements for the submodules of the AFE are also derived. Future work and challenges are discussed.

Die Bemessung von Bauwerken an oder in Fließgewässern erfordert die Kenntnis des statistischen Hochwasserregimes. Beispielsweise legen Hochwasserschutzkonzeptionen häufig ein Hochwasser zu Grunde, welches in einem Jahr mit der Wahrscheinlichkeit von 1/100 auftritt. Ein extremeres Hochwasser wird für den Nachweis der Standsicherheit großer Stauanlagen nach DIN 19700-12 mit einem Hochwasser der jährlichen Eintrittswahrscheinlichkeit von 1/10000 benötigt. Ein solches Hochwasser kann bereits wegen des instationären Klimas nicht allein aus Durchflussmessdaten abgeleitet, sondern lediglich idealisiert dargestellt werden. Das resultiert nicht zuletzt daraus, dass der Mensch natürlich Zeuge eines so unwahrscheinlichen Ereignisses werden kann. Jedoch kann er die Unwahrscheinlichkeit nicht nachweisen. Jedes Berechnungsschema, mit welchem ein so unwahrscheinliches Ereignis abgeschätzt werden soll, wird nur begrenzt zuverlässig sein. Das Ziel der Arbeit ist es daher, die Schätzung etwas zuverlässiger zu gestalten. Grundsätzlich gilt, dass ein Modell umso mehr bzw. sicherere Ergebnisse liefern kann, je mehr Daten in das Modell eingehen. Direkt mit dem Durchfluss gekoppelt sind Angaben zu historischen Hochwasserereignissen bzw. qualitative Einschätzungen kleinräumiger Ereignisse. Eine wichtige Datenquelle neben den Durchflussartigen ist der mit dem Durchfluss kausal verbundene Niederschlag und dessen zu vermutendes Maximum in einem Gebiet. Wird zusätzlich regional vorgegangen, können räumliche Aspekte und Strukturen in größeren Einzugsgebieten berücksichtigt werden. Diese stärken bzw. erweitern die lokalen Berechnungsgrundlagen und gewährleisten ein räumlich konsistentes Bild. Im Umkehrschluss kann das Durchflussregime regionalisiert werden, um Informationen an nicht bemessenen Orten bereitstellen zu können. Aus den genannten erweiterten Berechnungsgrundlagen lassen sich drei Anknüpfungspunkte schließen: (i) Es muss eine sehr flexible und dennoch plausible Darstellungsmöglichkeit des statistischen Niederschlagsregimes bis zum vermutlichen Maximum formuliert werden. (ii) Das entwickelte Niederschlagsregime muss mit dem Durchflussregime gekoppelt werden, um die Informationen nutzen zu können. (iii) Die anschließende Regionalisierung muss die verschachtelte baumartige Struktur hydrologischer Einzugsgebiete berücksichtigen. Punkt (i) wird durch eine zweigeteilte Verteilungsfunktion gelöst. Damit werden die ideale Darstellung des wahrscheinlicheren Bereiches und der plausible Verlauf bis zum Maximum miteinander verbunden. Bezüglich Punkt (ii) wird ein neues Kopplungsprinzip entwickelt. Dieses basiert auf der Annahme, dass ein je nach Gebiet gültiger maximaler Scheitelabflussbeiwert existiert, welcher asymptotisch erreicht wird. Im Ergebnis erhält die Durchflussverteilung mit der Abflussbeiwertapproximation einen oberen Grenzwert in Abhängigkeit von Niederschlagsmaximum und Scheitelabflussbeiwert. Entsprechend der Vorgaben in Punkt (iii) wird die Referenzpegelmethode entwickelt. Diese basiert darauf, dass ähnliche Einzugsgebiete äquivalente Hochwasserscheitel generieren. Damit können bekannte Hochwasserereignisse eines Referenzpegels auf unbeobachtete Teileinzugsgebiete übertragen werden. Bei der Wahl des Referenzpegels wird u.a. die Topologie der Einzugsgebiete berücksichtigt. Die gesamte Strategie kann auf große Untersuchungsgebiete angewandt werden. Am Beispiel sächsischer Flüsse wird die Vorgehensweise von der Datenhomogenisierung bis hin zum extremen Hochwasserdurchfluss an einem unbeobachteten Querschnitt erläutert. / The dimensioning of different constructions at and in streams respectively requires knowlegde on the flood situation at site. For instance flood protection concepts often base on a peak discharge of the annual recurrence probability of 1/100. A more severe flood of an annual recurrence probability of 1/10000 is used to confirm the stability of large dams following DIN 19700-12. Such a flood cannot be deduced from runoff data only, but rather shown in an idealised way. It results not least on the fact, that human can witness a very improbable flood event. But is it not possible to verify the improbability. Every modelling scheme that is confronted with the deduction of such an extreme flood event will be of limited reliability. The task\'s aim will therefore be to make the estimation more reliable. Generally the more data a model involves the more trustworthy the results will become. Directly coupled with runoff are historical flood data and qualitative details of small scale flood events respectively. Aside runoff information an important data source is precipitation data, which is coupled with runoff data in a causal way, and the possible maximum precipitation. If additionally whole regions are examined it is possible to consider regional facets and structures of larger catchments. These strengthen and expand local modelling basics and provide a regional consistent result. Vice versa the flood regime can be regionalised to gain information at unobserved cross sections. Out of the described expanded modelling basics follow three links: (i) It is necessary to find a flexible but still plausible formulation of the statistical precipitation regime until the probable maximum precipitation. (ii) The formulation of point i) has to be coupled with the flood regime to include these information. (iii) The adjacent regionalisation has to account for the nested and arboreal structure of hydrological catchments. Point (i) will be solved by a split distribution function. That allows the ideal display of the more probable domain as well as the characteristics until the probable maximum. Regarding point (ii) a new principle of coupling will be developed. It bases on the assumption that a regional maximum runoff coefficient exists and it will be gained asymptotically. As a result of the runoff coefficient approximation the runoff distribution function gets an upper limit depending on maximum precipitation and runoff coefficient. Respecting the guidelines in point (iii) the reference gauge method will be developed. It bases upon the fact, that likewise catchments generate equivalent peak discharges. For this reason it is possible to carry known peak discharges of a reference gauge onto unobserved subcatchments. Among other things the choice of a reference gauge accounts for the topology of the catchments. The whole strategy can be applied to large catchments what is exemplarily shown in Saxon streams. Beginning with a data homogenisation to the point of discharges of extreme low exceedance probabilities at unobserved cross sections the whole procedure is shown.

<p>A series of fusion techniques are developed and applied to EEG and pupillary recording analysis in a rapid serial visual presentation (RSVP) based image triage task, in order to improve the accuracy of capturing single-trial neural/pupillary signatures (patterns) associated with visual target detection.</p><p>The brain response to visual stimuli is not a localized pulse, instead it reflects time-evolving neurophysiological activities distributed selectively in the brain. To capture the evolving spatio-temporal pattern, we divide an extended (``global") EEG data epoch, time-locked to each image stimulus onset, into multiple non-overlapping smaller (``local") temporal windows. While classifiers can be applied on EEG data located in multiple local temporal windows, outputs from local classifiers can be fused to enhance the overall detection performance.</p><p>According to the concept of induced/evoked brain rhythms, the EEG response can be decomposed into different oscillatory components and the frequency characteristics for these oscillatory components can be evaluated separately from the temporal characteristics. While the temporal-based analysis achieves fairly accurate detection performance, the frequency-based analysis can improve the overall detection accuracy and robustness further if frequency-based and temporal-based results are fused at the decision level.</p><p>Pupillary response provides another modality for a single-trial image triage task. We developed a pupillary response feature construction and selection procedure to extract/select the useful features that help to achieve the best classification performance. The classification results based on both modalities (pupillary and EEG) are further fused at the decision level. Here, the goal is to support increased classification confidence through inherent modality complementarities. The fusion results show significant improvement over classification results using any single modality.</p><p>For crucial image triage tasks, multiple image analysts could be asked to evaluate the same set of images to improve the probability of detection and reduce the probability of false positive. We observe significant performance gain by fusing the decisions drawn by multiple analysts.</p><p>To develop a practical real-time EEG-based application system, sometimes we have to work with an EEG system that has a limited number of electrodes. We present methods of ranking the channels, identifying a reduced set of EEG channels that can deliver robust classification performance.</p> / Dissertation

Many-body perturbation theory and coupled-cluster theory, combined with carefully constructed basis sets, can be used to accurately compute the properties of small molecules. We applied a series of methods and basis sets aimed at reaching the ab initio limit to determine the barrier to planarity for ethylene cation. For potential energy surfaces corresponding to bond dissociation, a single Slater determinant is no longer an appropriate reference, and the single-reference hierarchy breaks down. We computed full configuration interaction benchmark data for calibrating new and existing quantum chemical methods for the accurate description of potential energy surfaces. We used the data to calibrate single-reference configuration interaction, perturbation theory, and coupled-cluster theory and multi-reference configuration interaction and perturbation theory, using various types of molecular orbitals, for breaking single and multiple bonds on ground-state and excited-state surfaces. We developed a determinant-based method which generalizes the formulation of many-body wave functions and energy expectation values. We used the method to calibrate single-reference and multi-reference configuration interaction and coupled-cluster theories, using different types of molecular orbitals, for the symmetric dissociation of water. We extended the determinant-based method to work with general configuration lists, enabling us to study, for the first time, arbitrarily truncated coupled-cluster wave functions. We used this new capability to study the importance of configurations in configuration interaction and coupled-cluster wave functions at different regions of a potential energy surface.

The work presented in this thesis is dedicated to developing inexpensive quantum-chemical models that are able to produce smooth and physically correct potential energy curves for the dissociation of single covalent bonds. It is well known that the energies produced by many ab initio theories scaling as the fifth order with the system size (for instance, second-order Moller-Plesset (MP2) and Epstein-Nesbet perturbation theories) diverge at large interatomic separations. We show that the divergent behavior of such perturbation schemes is due to a small number of terms in the energy expressions. Then, we demonstrate that the self-consistent replacement of these terms by their analogs from the coupled cluster theory (such as CCSD) allows one to redress the erroneous behavior of the perturbation theories without the damage to the overall scaling. We also investigate the accuracy of these hybrid perturbation theory-coupled cluster theories near equilibrium geometry. Judging from the computed spectroscopic constants and shapes of the potential energy curves, one such model, denoted MP2-CCSD(II) in this work, performs consistently better than the MP2 theory at essentially the same computational cost.

A mobile phone antenna with a radiating coupling feed is presented. By using the radiating coupling feed, the conventional coupled-fed loop antenna and coupled-fed shorted monopole antenna can be efficiently incorporated into the antenna structure and respectively excite a wide band resonant mode to cover GSM850/900 and GSM1800/1900/UMTS/LTE2300/2500 for the seven-band operation. Besides, the antenna can be in compact integration with the extended ground plane such that more electronic components in the mobile phone can be accommodated in the practical applications. In order to study the near-field radiation characteristics of the antenna, SAR and HAC are also simulated and analyzed.