When antennas are placed closely spaced together, the mutual coupling and spatial correlation effects undermine the advantages provided by multiple input and multiple output (MIMO) antennas. In this thesis, we compare and analyze the performance of digital beamforming, fixed radio frequency (RF) beamforming and element based patterning with closely spaced antenna systems. In the case where only one RF-chain is available, we have demonstrated performance improvements using RF beamforming-based MIMO processing instead of element-based MIMO processing with closely spaced metamaterial antennas. The result indicates that even without mutual coupling, antenna based MIMO processing is greatly impacted when moving from rich to correlated scattering environments. In the second half of the thesis, we investigate the switch and examine receiver combining (SEC) technique. We derive the switching rate of SEC and show that even though it has the same outage probability as traditional selection combining, it has a significantly lower switching rate.

When antennas are placed closely spaced together, the mutual coupling and spatial correlation effects undermine the advantages provided by multiple input and multiple output (MIMO) antennas. In this thesis, we compare and analyze the performance of digital beamforming, fixed radio frequency (RF) beamforming and element based patterning with closely spaced antenna systems. In the case where only one RF-chain is available, we have demonstrated performance improvements using RF beamforming-based MIMO processing instead of element-based MIMO processing with closely spaced metamaterial antennas. The result indicates that even without mutual coupling, antenna based MIMO processing is greatly impacted when moving from rich to correlated scattering environments. In the second half of the thesis, we investigate the switch and examine receiver combining (SEC) technique. We derive the switching rate of SEC and show that even though it has the same outage probability as traditional selection combining, it has a significantly lower switching rate.

Annular gas seal clearances were simulated with closely spaced parallel plates using a Flat?Plate tester. The device is designed to measure the pressure gradient along the test specimen. The main function of the Flat?Plate tester is to provide friction factor data and measure dynamic pressure oscillations. A detailed description of the test facility is described, and a theory for determining the friction factor is reviewed. Three clearances were investigated: 0.635, 0.381, and 0.254 mm. Tests were conducted at three different inlet pressures (84, 70, and 55 bars), producing Reynolds numbers range from 50,000 to 700,000. Three surface configurations were tested including smooth?on-smooth, smooth?on?hole, and hole?on?hole. The Hole?pattern plates are identical with the exception of the hole depth. The results indicate that, for the smooth?on?smooth and smooth?on?hole configurations, the friction factor remains constant or increases slightly with increasing Reynolds numbers. Moreover, the friction factor increases as the clearance between the plates increases. However, the results from the hole?on-hole configurations are quite different. A "friction?factor jump" phenomenon was observed, and the Helmholtz frequency was detected on the frequency spectra.

Placing wave energy devices within close proximity to each other can be beneficial as the costs of deployment, maintenance and infrastructure are reduced significantly compared to if the devices are deployed in isolation. A mathematical model is presented in this thesis which combines linear wave theory with a series of linear driven harmonic oscillators to model an array (group) of floating wave energy devices which move predominantly in heave (vertically) in a train of incident regular waves. Whilst similar mathematical models have been used previously to investigate interactions between fluids and groups of structures, much of the published work does not address array configurations or device constraints that are relevant to designers of structure-supported array devices. The suitability of linear theory for application to closely spaced arrays is assessed in this thesis through comparison to small-scale experimental data and by evaluation of the magnitude of second-order hydrodynamic forces. Values of mechanical damping and mass are determined for each element of an array in order to achieve the maximum power from an array of floats without requiring the knowledge of the motion of every float within the array in order to apply the forces to any one float. Further to this, the analysis of floats of varying geometry is performed in order to assess the possibility of array optimisation through the variation of float geometries within a closely spaced array.It is shown in this thesis that linear theory provides a reasonable prediction of the response of floats that are sufficiently close together to interact for most wave frequencies to which the arrays are likely to be subjected. Under the assumption of easily implementable mechanical damping, it is determined that the power output from an array of floats of equal geometry can be increased by specifying different magnitudes of mechanical damping on each float independently of the radiation damping. Variations in submerged float geometries for the purpose of manipulating array characteristics according to the incident wave frequency are best applied through the variation in draft of a single geometry. Variations in submerged float geometry which occur close to the free surface are found to be of the greatest significance. Where the float is uniform in cross-section, the most appropriate method to select float drafts within an array is found to be based on the evaluation of the total damping on each float.

<p>  </p> <p>Post-installed bonded anchors find a wide range of application in construction industry due to their versatility and flexibility in accommodating diverse engineering needs. Engineering practices often encounter situations where space constraints within a building member lead to unusual anchor group geometric configurations. Multiple anchor groups with small inter-group spacing (closely spaced anchor groups) emerge as a result. The stress-field and overall behaviour of individual anchor groups is affected by the presence of other closely spaced anchor groups. Situation become more intricate when these closely-spaced anchor groups are installed in close proximity of edge, subjected to different loading conditions and involve different eccentric loading scenarios.</p> <p>The current design standards provide limited and very conservative guidelines for designing and analysing closely spaced anchor groups where spacing between neighbouring anchor groups is less than the critical anchor spacing. This paper presents a 3-dimensional (3D), Finite Element (FE) study on the tension and shear behaviour of closely spaced anchor groups under various geometric and loading conditions. Different parameters such as inter-group spacing, presence of nearby edge and loading positions (eccentricities and symmetry of loading) for models loaded in tension, are numerically investigated. In case of shear loads, anchor groups with similar / different edge distance in the direction of loading and different loading positions are investigated. In this study, concrete cone break-out failure for tension loaded anchor groups and concrete edge failure for shear loaded anchor groups are considered as critical failure modes. </p> <p>Numerical analysis is carried out using microplane model for concrete with relaxed kinematic constraint as the constitutive law. 3D, finite element, Mascroscopic Space Analysis (MASA) program is used to numerically investigate the behavior of closely spaced anchor groups under different geometric and loading conditions. The numerical modelling approach is first verified and validated against available experimental results on anchor groups and then used to carry out a detailed and systematic study. Parametric study on a wide range of geometric configurations containing multiple anchor groups subjected to different loading positions (centric / eccentric) is carried out.</p> <p>Comparison study is conducted to check the numerical resistance capacities against analytical values calculated using existing concrete capacity design (CCD) method incorporating existing reduced embedment depth / edge distance approach and newly developed virtual edge approach. The virtual edge approach considers a virtual edge to assign individual tributary areas to individual anchor groups in calculating the concrete breakout resistance of anchorages. Evaluation of results indicate that virtual edge approach is appropriate, rational and reasonably conservative to consider the influence of presence of neighbouring anchor group on the capacity of given anchorage. A new set of guidelines is recommended to design closely space anchor groups for arbitrary geometric and loading conditions.</p>

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A series of static lateral load tests were conducted on a group of fifteen piles arranged in a 3x5 pattern. The piles were placed at a center-to-center spacing of 3.92 pile diameters. A single isolated pile was also tested for comparison to the group response. The subsurface profile consisted of cohesive layers of soft to medium consistency underlain by interbedded layers of sands and fine-grained soils. The piles were instrumented to measure pile-head deflection, rotation, and load, as well as strain versus pile depth.

In this dissertation, sparse processing of signals for directions-of-arrival (DoAs) estimation is addressed in the framework of Compressive Sensing (CS). In particular, DoAs estimation problem for different types of sources, systems, and applications are formulated in the CS paradigm. In addition, the fundamental conditions related to the ``Sparsity'' and ``Linearity'' are carefully exploited in order to apply confidently the CS-based methodologies. Moreover, innovative strategies for various systems and applications are developed, validated numerically, and analyzed extensively for different scenarios including signal to noise ratio (SNR), mutual coupling, and polarization loss. The more realistic data from electromagnetic (EM) simulators are often considered for various analysis to validate the potentialities of the proposed approaches. The performances of the proposed estimators are analyzed in terms of standard root-mean-square error (RMSE) with respect to different degrees-of-freedom (DoFs) of DoAs estimation problem including number of elements, number of signals, and signal properties. The outcomes reported in this thesis suggest that the proposed estimators are computationally efficient (i.e., appropriate for real time estimations), robust (i.e., appropriate for different heterogeneous scenarios), and versatile (i.e., easily adaptable for different systems).