Image rendering is the process of creating realistic computer images from  geometric models and physical laws of light and reflection. This master thesis deals mainly with the numerical intricacies of implementing an image renderer using spherical harmonics. It investigates how to calculate the reflection of light in a surface using the Phong model, and employs ray tracing to create a realistic image of a geometric model. Further, it investigates different ways of calculating the spherical harmonic representation of a function defined on the sphere. The thesis also deals with the implementation of self-shadowing, and the effects of adding this component to the rendering equation.

Spectrum sensing plays a key role for radio resource awareness in cognitive radio. To enhance the capabilities of cognitive radio nodes, exploiting the spatial resource in addition to frequency and time re-sources seems reasonable. This thesis investigates the possibility of exploiting the spatial resources during sensing and transmission using sector antennas which is also termed as directional spectrum sensing and transmission. The measured radiation patterns from fabricated antenna and radiation patterns obtained from analytical expressions representing circular array of dipole are used for performance analysis. A ray tracer tool is used for modelling the urban environment as well as for wave propagation simulation. The power angular profiles obtained at different locations are further processed in MATLAB using measured and analytical radiation patterns to evaluate the performance in terms of spatial opportunity and detection of weak primary signals. The results show that exploiting the spatial dimension in spectrum sensing using sector antennas increase the opportunities for secondary communication and also improves the detection of primary signals as compared with an omni-directional antenna. Additionally, directional sensing and trans-mission are studied together using analytical radiation patterns. The results show that the service probability as well as range of communica-tion increases with an increase in number of sectors but saturation is achieved when nine sectors are used, indicating that six sectors antenna is the optimum choice for exploring the spatial resource in cognitive radio in a typical multipath urban environment.

During magnetically disturbed periods, the spatially and temporally structured electron precipitation in the auroral zone creates a significant population of thermal secondary ions. Acceleration mechanisms exist that are capable of energizing the thermal population to suprathermal energies (1 eV to 1 keV). Suprathermal ions escape into the magnetosphere and undergo "bounce" motion along magnetic field lines. These ions are bound to the magnetic flux tubes, which undergo ExB convective drift within the magnetosphere. Magnetospheric convection transports flux tubes of bouncing suprathermal ions through the auroral zone and the subauroral polarization stream (SAPS) regions. Precipitating suprathermal ions enhance ionospheric plasma density structure and constitute a possible source for the enhanced echo occurrence observed by ground-based radars in the SAPS region. Satellite energy spectrometer data often show multiple bands of suprathermal particles with enhanced number and energy flux, and with an energy increase with increasing latitude. The present work examines the hypothesis that these signatures are the result of thermal secondary ions that have been accelerated out of the auroral ionosphere over the short time scales characterizing bursts of intense auroral electron precipitation. The analysis of three events of energy-dispersed ion signatures was facilitated by three-dimensional ion tracing software developed for this thesis. The short-lived acceleration hypothesis can account for the energy-dispersed ion signatures if there exist inter-hemispheric field aligned potentials of the order of 100 V. If the source of the ions is within the auroral zone, the suprathermal ions observed in the SAPS region are most likely to be O+ ions. The long bounce period of O+ (compared to H+) allows convection to transport O+ auroral ions equatorward through a convection reversal, into the SAPS region during a single half-bounce.

Neurovascular models have played an important role in understanding neuronal function or medical conditions. In the past few decades, only small volumes of neurovascular data have been available. However, huge data sets are becoming available with high throughput instruments like the Knife-Edge Scanning Microscope (KESM). Therefore, fast and robust tracing methods become necessary for tracing such large data sets. However, most tracing methods are not effective in handling complex structures such as branches. Some methods can solve this issue, but they are not computationally efficient (i.e., slow). Motivated by the issue of speed and robustness, I introduce an effective and efficient fiber tracing algorithm for 2D and 3D data. In 2D tracing, I have implemented a Moving Window (MW) method which leads to a mathematical simplification and noise robustness in determining the trace direction. Moreover, it provides enhanced handling of branch points. During tracing, a Cubic Tangential Trace Spline (CTTS) is used as an accurate and fast nonlinear interpolation approach. For 3D tracing, I have designed a method based on local maximum intensity projection (MIP). MIP can utilize any existing 2D tracing algorithms for use in 3D tracing. It can also significantly reduce the search space. However, most neurovascular data are too complex to directly use MIP on a large scale. Therefore, we use MIP within a limited cube to get unambiguous projections, and repeat the MIP-based approach over the entire data set. For processing large amounts of data, we have to automate the tracing algorithms. Since the automated algorithms may not be 100 percent correct, validation is needed. I validated my approach by comparing the traced results to human labeled ground truth showing that the result of my approach is very similar to the ground truth. However, this validation is limited to small-scale real-world data due to the limitation of the manual labeling. Therefore, for large-scale data, I validated my approach using a model-based generator. The result suggests that my approach can also be used for large-scale real-world data. The main contributions of this research are as follows. My 2D tracing algorithm is fast enough to analyze, with linear processing time based on fiber length, large volumes of biological data and is good at handling branches. The new local MIP approach for 3D tracing provides significant performance improvement and it allows the reuse of any existing 2D tracing methods. The model-based generator enables tracing algorithms to be validated for large-scale real-world data. My approach is widely applicable for rapid and accurate tracing of large amounts of biomedical data.

Two experimental rainfall simulation plots in the Edwards Aquifer region of Texas were established to measure the effects of brush clearing on surface and subsurface water movement pathways. Multi-stage rainfall simulations were carried out at a site with Juniperus ashei (ashe juniper) cover both before and after brush removal, with three replications of a particular rainfall event for each vegetation condition. Similar simulations were carried out on a plot with a longstanding grass cover. Both plots included trenches at their downhill ends for observation of shallow lateral subsurface flow. Canopy interception was found to represent a major water loss, with interception of 32.7 mm for an average 166 mm, 5.25 hr rainfall event. Brush clearing had little impact on surface runoff, with no overland flow occurring at the juniper plot for either vegetation condition, while 31.9 percent of applied rainfall moved as overland flow at the grass plot. This difference was attributed to differences in the structure and permeability of the epikarst. Brush removal caused significant (90 percent confidence level) reduction in shallow lateral subsurface flow into the trench after brush removal, with 56.7 percent of water reaching the surface entering the trench for the pre-cut condition and only 43.4 percent for the post-cut condition. However, subsurface water movement through other pathways increased from 31.0 to 54.1 percent after brush removal. This additional water, due to removal of canopy interception, could either move off-site through conduit and fracture flow or remain on site as storage in conduits, unconsolidated caliche/marl layers, or in soil pockets. Two tracer tests with fluorescent dyes were also conducted using simulated rainfall to assess discrete flow paths discharging into the trench at the downhill end of the juniper plot. Analysis of samples from sixteen outlet locations revealed that not all areas of the plot were connected hydraulically to the trench. Additionally, subsurface flow paths were found to have a high degree of interconnection, linking conduit flow outlets with multiple inlet locations on the plot surface. Conduits showed strong connection with an area surrounding juniper vegetation, with rapid water flow (up to 2.4 m/h) from this area.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / The extremely large electrical-size and complexity of terrain scene poses great challenge in channel modeling of aeronautic telemetry. It becomes even more difficult if severe multipath and fading present due to scattering and attenuation of ground, terrain objects and precipitation [Rice, 2004]. This is critical in more sophisticated test scenarios involving low flying unmanned air vehicles and helicopters tested over water at high sea states, in hilly terrain, or even over urban environment. Conventional ray tracing and simple Fresnel reflection are not sufficient to characterize such complex channels. Hence, the novel bidirectional analytic ray tracing and radiative transfer (RT²) is proposed for advanced telemetry channel modeling.

Since Mobile network operator (MNO) relies on many Business Support Systems (BSS) and Operation Support Systems (OSS) it should be assured that operator’s systems supports the requirements of the future.This thesis shall focus on the “start-to-end” aspects that must be considered to ensure that International Roaming continues to operate flawless. The thesis experience Long Term Evolution (LTE) in case of international roaming by measuring the end to end location update delay.In order to evaluate the LTE performance of international roaming, the delay time has been measured by the means of tracing tools for several different international roamers and the results has been compared with the results achieved for local user. The outcome has been compared with the respecting results in 3G network the statistical results has been provided and the graphs has been plotted to study the performance.Based on the results obtain on this thesis, it has been concluded that local user acts more stable to get attach to the network, i.e. there are less fluctuation in delay times for local user. Also the delay time in 3G networks is more than the LTE networks, however 3G networks acts more stable and there are less fluctuation to get connects to 3G networks.

Faults are common-place and inevitable in complex applications. Hence, automated techniques are necessary to analyze failed executions and debug the application to locate the fault. For locating faults in programs, dynamic slices have been shown to be very effective in reducing the effort of debugging. The user needs to inspect only a small subset of program statements to get to the root cause of the fault. While prior work has primarily focussed on single-threaded programs, this dissertation shows how dynamic slicing can be used for fault location in multithreaded programs. This dissertation also shows that dynamic slices can be used to track down faults due to data races in multithreaded programs by incorporating additional data dependences that arise in the presence of many threads. In order to construct the dynamic slices, dependence traces are collected and processed. However, program runs generate traces in the order of Gigabytes in a few seconds. Hence, for multithreaded program runs that are long-running, the process of collecting and storing these traces poses a significant challenge. This dissertation proposes two techniques to overcome this challenge. Experiments indicate that the techniques combined can reduce the size of the traces by 3 orders of magnitude. For applications that are critical and for which down time is highly detrimental, techniques for surviving software failures and letting the execution continue are desired. This dissertation proposes one such technique to recover applications from a class of faults that are caused by the execution environment and prevent the fault in future runs. This technique has been successfully used to avoid faults in a variety of applications caused due to thread scheduling, heap overflow, and malformed user requests. Case studies indicate that, for most environment bugs, the point in the execution where the environment modification is necessary can be clearly pin-pointed by using the proposed system and the fault can be avoided in the first attempt. The case studies also show that the patches needed to prevent the different faults are simple and the overhead induced by the system during the normal run of the application is less than 10 \%, on average.

Developing automated techniques for identifying a fault candidate set (i.e., subset of executed statements that contains the faulty code responsible for the failure during a program run), can greatly reduce the effort of debugging. Over 15 years ago precise dynamic slicing was proposed to identify a fault candidate set as consisting of all executed statements that influence the computation of an incorrect value through a chain of data and/or control dependences. However, the challenge of making precise dynamic slicing practical has not been addressed. This dissertation addresses this challenge and makes precise dynamic slicing useful for debugging realistic applications. First, the cost of computing precise dynamic slices is greatly reduced. Second, innovative ways of using precise dynamic slicing are identified to produce small failure candidate sets. The key cause of high space and time cost of precise dynamic slicing is the very large size of dynamic dependence graphs that are constructed and traversed for computing dynamic slices. By developing a novel series of optimizations the size of the dynamic dependence graph is greatly reduced leading to a compact representation that can be rapidly traversed. Average space needed is reduced from 2 Gigabytes to 94 Megabytes for dynamic dependence graphs corresponding to executions with average lengths of 130 Million instructions. The precise dynamic slicing time is reduced from up to 20 minutes for a demand-driven algorithm to 16 seconds. A compression algorithm is developed to further reduce dependence graph sizes. The resulting representation achieves the space efficiency such that the dynamic execution history of executing a couple of billion instructions can be held in a Gigabyte of memory. To further scale precise dynamic slicing to longer program runs, a novel approach is proposed that uses checkpointing/logging to enable collection of dynamic history of only the relevant window of execution. Classical backward dynamic slicing can often produce fault candidate sets that contain thousands of statements making the task of identifying faulty code very time consuming for the programmer. Novel techniques are proposed to improve effectiveness of dynamic slicing for fault location. The merit of these techniques lies in identifying multiple forms of dynamic slices in a failed run and then intersecting them to produce smaller fault candidate sets. Using these techniques, the fault candidate set size corresponding to the backward dynamic slice is reduced by nearly a factor of 3. A fine-grained statistical pruning technique based on value profiles is also developed and this technique reduces the sizes of backward dynamic slices by a factor of 2.5. In conclusion, this dissertation greatly reduces the cost of precise dynamic slicing and presents techniques to improve its effectiveness for fault location.

The health, safety, comfort and productivity of a room’s occupants is greatly influenced by the sound field within it. An acoustical engineer is often consulted during the design of a room to prevent or alleviate unwanted acoustical problems. Prediction models are often used to find the most cost-effective solution to a given acoustical problem. The accuracy of sound-field prediction varies with the particular model, as do the parameters predicted. Most models only predict sound-pressure levels. Many only predict energetic quantities, ignoring wave phase and, therefore, interference and modal effects in rooms. A ray-tracing model, capable of predicting sound-pressure level, reverberation time and lateral energy fraction was translated into MATLAB code and modified to increase accuracy by including phase. Modifications included phase effects due to path length travelled and phase changes imparted by surface reflections as described by complex reflection coefficients. Further modifications included predicting steady-state and transient sound-intensity levels, providing information on the direction of sound-energy flow. The modifications were validated in comparison with free-field theory and theoretical predictions of sound fields in the presence of a single surface. The complex reflection coefficients of four common building materials were measured using two methods—an impedance tube and the spherical-decoupling method. Using these coefficients, the modified program was compared with experimental data measured in configurations involving one or more surfaces made of these materials, in an anechoic chamber, a scale-model room, and a full-scale office space. Prediction accuracy in the anechoic chamber, and in the presence of a single reflecting surface, greatly improved with the inclusion of phase. Further comparison with full-scale rooms is required before the accuracy of the model in such rooms can be evaluated definitively.