The importance of seismic anisotropy has been recognized by the oil industry since its first observation in hydrocarbon reservoirs in 1986, and the application of seismic anisotropy to solve geophysical problems has been keenly pursued since then. However, a lot of problems remain, which have limited the applications of the technology. Nowadays, more and more 3D multi-component seismic data with wide-azimuth are becoming available. These have provided more opportunities for the study of seismic anisotropy. My thesis has focused on the study of using seismic anisotropy in 3D multi-component seismic data to characterize subsurface fractures, improve converted wave imaging and detect fluid content in fractured reservoirs, all of which are important for fractured reservoir exploration and monitoring. For the use of seismic anisotropy to characterize subsurface fracture systems, equivalent medium theories have established the link between seismic anisotropy and fracture properties. The numerical modelling in the thesis reveals that the amplitudes and interval travel-time of the radial component of PS converted waves can be used to derive fracture properties through elliptical fitting similar to P-waves. However, sufficient offset coverage is required for either the P- or PS-wave to reveal the features of elliptical variation with azimuth. Compared with numerical modelling, seismic physical modelling provides additional insights into the azimuthal variation of P and PS-wave attributes and their links with fracture properties. Analysis of the seismic physical model data in the thesis shows that the ratio of the offset to the depth of a target layer (offset-depth ratio), is a key parameter controlling the choice of suitable attributes and methods for fracture analysis. Data with a small offset-depth ratio from 0.7 to 1.0 may be more suitable for amplitude analysis; whilst the use of travel time or velocity analysis requires a large offset-depth ratio above 1.0, which can help in reducing the effect of the acquisition footprint and structural imprint on the results. Multi-component seismic data is often heavily contaminated with noise, which will limit its application potential in seismic anisotropy analysis. A new method to reduce noise in 3D multi-component seismic data has been developed and has proved to be very helpful in improving data quality. The method can automatically recognize and eliminate strong noise in 3D converted wave seismic data with little interference to useful reflection signals. Component rotation is normally a routine procedure in 3D multi-component seismic analysis. However, this study shows that incorrect rotations may occur for certain acquisition geometry and can lead to errors in shear-wave splitting analysis. A quality control method has been developed to ensure this procedure is correctly carried out. The presence of seismic anisotropy can affect the quality of seismic imaging, but the study has shown that the magnitude of the effects depends on the data type and target depth. The effects of VTI anisotropy (transverse isotropy with a vertical symmetry axis) on P-wave images are much weaker than those on PS-wave images. Anisotropic effects decrease with depth for the P- and PS-waves. The real data example shows that the overall image quality of PS-waves processed by pre-stack time migration has been improved when VTI anisotropy has been taken into account. The improvements are mainly in the upper part of the section. Monitoring fluid distribution is an important task in producing reservoirs. A synthetic study based on a multi-scale rock-physics model shows that it is possible to use seismic anisotropy to derive viscosity information in a HTI medium (transverse isotropy with a horizontal symmetry axis). The numerical modelling demonstrates the effects of fluid viscosity on medium elastic properties and seismic reflectivity, as well as the possibility of using them to discriminate between oil and water saturation. Analysis of real data reveals that it is hard to use the P-wave to discriminate oil-water saturation. However, characteristic shear-wave splitting behaviour due to pore pressure changes demonstrates the potential for discriminating between oil and water saturation in fractured reservoirs.

Approved for public release, distribution is unlimited / The purpose of this research was to examine the effects of frequency, and polarization on radio wave propagation in urbanized areas for unmanned aerial vehicle (UAV) data links, and command and control. The transmission from a UAV operating over a small city was simulated using the Urbana Wireless Toolset. Parameters that were varied include frequency, antenna polarization, UAV altitude, and building materials. Multiple reflections and diffractions were included in the simulation. In each case signal contours were generated at discrete frequencies over a 50 MHz bandwidth. It was observed that the signal levels varied up to over the bands at a fixed observation point due to frequency-dependent reflection and diffraction. / 1st Lieutenant, Turkish Air Force

Approved for public release; distribution is unlimited. / Setup is defined as the superelevation of mean water surface within the surfzone and is caused by the reduction in wave momentum shoreward of the breaking point and compensating positive pressure gradient. Data were acquired north of Scripps Canyon on a gently sloping section of beach, which was homogenous in along-shore morphology, during the Nearshore Canyon Experiment, 2004. Pressure sensors were deployed both above and below the bed. Wave heights and radiation stress (wave-induced momentum) were calculated using linear theory transfer functions. Wave heights measured using pressure sensors in the water column had a positive bias compared with the buried pressure sensors, which it is presumed due to the Bernoulli effect of flow past the orifices. Predicted setup based on numerically solving the cross-momentum equation forced with the measured radiation stresses underestimates the observed setup by 40 percent in the mean. This is consistent with previous studies. / Lieutenant, United States Navy

Accurate predictions and understanding of littoral and coastal wave conditions are of major importance to military operations and civilian coastal zone management. Although WaveWatchIII (WW3) is used by many operational forecasting centers around the world, there is a lack of field studies to evaluate its accuracy in regional applications and under extreme conditions, such as Hurricanes. Data from seven National Data Buoy Center (NDBC) buoys in the Gulf of Mexico, together with an array of pressure and pressure-velocity sensors deployed on the Florida Panhandle shelf during the Office of Naval Research (ONR) SAX04 experiment, were used to test WW3 predictions of extreme waves generated by Hurricane Ivan. The model predicts large differences between wave conditions on the left and right sides of the hurricane track owing to the difference in "dwell time" between wave propagating against and with the storm. Analysis reveals a tendency to predict smaller wave heights and later arrival of hurricane swell than is observed. Additionally, the default operational setting for dissipation by bottom friction yields too much dissipation on the continental shelf. Overall, the agreement between observations and model predictions is reasonable.

pulation. Two methods were examined for calculating breaking wave dissipation rates for particularly robust days (110.5 -114.5). Velocity data were acquired using two electromagnetic current meters over the vertical mounted on a tower at mid-surf zone. The first method identified individual bores, which were ensemble averaged by phase over 30 minute records to obtain wave number spectra invoking Taylor's frozen turbulence hypothesis. Maximum dissipation rates underneath the bore cycle were shown to lag behind the sea surface elevation. The second method used 30 minute ensemble averaged spectra to obtain dissipation after Trowbridge and Elgar (2001). Dissipation rates calculated underneath each bore segment were orders of magnitude smaller when compared to the ensemble averaged technique.

Orthogonal frequency division multiplexing (OFDM) is an efficient multi-carrier modulation technique which can be combined with transmitter and receiver diversity communication systems. Maximal ratio combining (MRC) and space-time block coding (STBC) can be used in conjunction with receiver and transmitter diversity in order to increase the communication system's performance. For these systems, channel estimation and tracking must be performed since the receiver requires channel state information for decoding. In this thesis, block-type and comb-type channel estimation algorithms for OFDM systems over multipath fading channels are studied and simulated. Performance results using simulated frequency-selective channels are presented.

The complex permittivity ( )Ì and permeability ( æ) of a material determine the response of the material to electromagnetic radiation. Usually, the real parts of Ì and æ are positive for naturally occurring materials at microwave frequencies. Metamaterials are engineered media that are designed to have either a negative permittivity or permeability or both. Negative permeability and negative permittivity would cause electromagnetic waves traveling through this medium to exhibit unusual characteristics such as power flow in a direction opposite to the phase velocity. In this thesis, the wave matrix approach is used to calculate the total reflection and transmission coefficients of a multilayered structure. The method is applicable to all types of materials, including metamaterials. Several layered configurations are studied including both metamaterial and conventional dielectric layers. A MATLAB program is developed to examine the effects of frequency, angle of incidence and polarization. The results are compared to published data. Potential applications of metamaterials are also discussed.

ornia. Data were first corrected for dropouts. Next the data quality was verified through a consistency check on the redundant velocity measurements of opposing beams, an evaluation of high frequency spectral noise levels, and a comparison of velocity and pressure measurements using linear wave theory. Finally wave height and direction spectra estimated from the ADCP data were compared to data from a directional wave buoy. The analysis revealed that the ADCP data can suffer from low signal to noise ratios in benign conditions and deeper water. Whereas the wave height estimates are sensitive to these errors, the wave direction estimates are surprisingly robust.

The phenomenon of spiral wave propagation in Belousov-Zhabotinsky media is a remarkable example of self-organisation. This distinctive waveform arises in a variety of excitable systems. The primary objective of the work described in this thesis is the construction and analysis of deterministic reaction-diffusion models in terms of partial differential equations, to explain the local and global geometry of the spiral pattern. The secondary objective is to design experiments that enable observation and recording of evolving chemical waves in three dimensional Belousov-Zhabotinsky media. A mathematical formulation of the one dimensional A-w system based on a hierarchy of trial phase functions is introduced. A Schr8dinger type boundary value problem in an eigen sub-domain is established; an algebraic formula for the wave number spectrum and an analytical representation for the concentration amplitude are derived. This formulation suggests a piece-wise linear approach to X-w systems in higher dimensions. The concentrations are expressible in terms of real combinations of solutions to the Helmholtz equation with complex wave number and the solutions are matched by using continuity, differentiability and threshold conditions. A detailed analysis of the existence of solutions to piece-wise linear A-w systems in two dimensions is presented; existence is demonstrated by solving the matching equations. A stability analysis completes the discussion. Plots of the concentration contours characterised by the matching parameters are included. These contours simulate the cross-section of the scroll wave observed in experiments carried out in three dimensional media. The experimental design allows direct observation of undistorted three dimensional chemical waves in situ. The kinematics, dynamics and transformations of a variety of three dimensional scroll-based structures are recorded. The dominant waveforms are simple scroll waves. In addition, transient but significant events such as fission of a complex structure are recorded.

Quasi-periodic disturbances have been observed in the outer solar atmosphere for many years. Although first interpreted as upflows (Schrijver et al. (1999)), they have been widely regarded as slow magneto-acoustic waves, due to their observed velocities and periods. Here we conduct a detailed analysis of the velocities of these disturbances across several wavelengths using the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We analysed 41 examples, including both sunspot and non-sunspot regions of the Sun. We found that the velocities of propagating disturbances (PDs) located at sunspots are more likely to be temperature dependent, whereas the velocities of PDs at non-sunspot locations do not show a clear temperature dependence. This suggests an interpretation in terms of slow magneto-acoustic waves in sunspots but the nature of PDs in non-sunspot (plage) regions remains unclear. Finally, we found that removing the contribution due to the cooler ions in the 193 wavelength suggests that a substantial part of the 193 emission of sunspot PDs can be attributed to the cool component of 193. Phase mixing is a well known and studied phenomenon in the solar corona, to enhance the dissipation of Alfvén waves (Heyvaerts and Priest (1982)). In this study we run numerical simulations of a continuously driven Alfvén wave in a low beta plasma along a uniform magnetic field. We model phase mixing by introducing a density inhomogeneity. Thermal conduction is then added into the model in the form of Braginskii thermal conduction. This acts to transport heat along the magnetic field. A parameter study will be carried out to investigate how changing the density structure and other parameters changes the results. We go on to consider the effect of wave reflection on phase mixing. We found that wave reflection has no effect on the damping of Alfvén waves but increases the heat in the system. We also consider a more realistic experiment where we drive both boundaries and study how the loop is heated in this situation. We also study what effect changing the frequency of one of the drivers so there is a small difference between the frequencies (10%) and a large difference (50%). We find the general behaviour is similar, but the heat is tilted. We have investigated basic phase mixing model which incorporates the mass exchange between the corona and the chromosphere. Chromospheric evaporation is approximated by using a non dimensional version of the RTV (Rosner et al. (1978)) scaling laws, relating heating (by phase mixing of Alfvén waves), density and temperature. By combining this scaling law with our numerical MHD model for phase mixing of Alfvén waves, we investigate the modification of the density profile through the mass up flow. We find a rapid modification of the density profile, leading to drifting of the heating layers. We also find that similar results are own seen in the propagating Alfvén wave case when we incorporate the effects of reflection.