Determining The Location of an Impact Site from Bloodstain Spatter Patterns: Computer-Based Analysis of Estimate Uncertainty.

The estimation of the location in which an impact event took place from its resultant impact spatter bloodstain pattern can be a significant investigative issue in the reconstruction of a crime scene. The bloodstain pattern analysis methods through which an estimate is constructed utilise the established bloodstain pattern analysis principles of spatter bloodstain directionality, impact angle calculation, and straight-line trajectory approximation. Uncertainty, however, can be shown to be present in the theoretical definition and practical approximation of an impact site; the theoretical justification for impact angle calculation; spatter bloodstain sample selection; the dimensional measurement of spatter bloodstain morphologies; the inability to fully incorporate droplet flight dynamics; and the limited numerical methods used to describe mathematical estimates. An experimental computer-based research design was developed to investigate this uncertainty. A series of experimental impact spatter patterns were created, and an exhaustive spatter bloodstain recording methodology developed and implemented. A computer application was developed providing a range of analytical approaches to the investigation of estimate uncertainty, including a three-dimensional computer graphic virtual investigative environment. The analytical computer application was used to generate a series of estimates using a broad spatter bloodstain sampling strategy, with six potentially probative estimates analysed in detail. Two additional pilot projects investigating the utility of a sampled photographic recording methodology and an automated image analysis approach to spatter bloodstain measurement were also conducted. The results of these analyses indicate that, with further development, the application of similar analytical approaches to the construction and investigation of an estimate could prove effective in minimising the effect that estimate uncertainty might have on informing the conclusions of this forensic reconstructive process, and thereby reaffirm the scientific expert evidential status of estimate techniques within legal contexts

Determining The Location of an Impact Site from Bloodstain Spatter Patterns: Computer-Based Analysis of Estimate Uncertainty.

The estimation of the location in which an impact event took place from its resultant impact spatter bloodstain pattern can be a significant investigative issue in the reconstruction of a crime scene. The bloodstain pattern analysis methods through which an estimate is constructed utilise the established bloodstain pattern analysis principles of spatter bloodstain directionality, impact angle calculation, and straight-line trajectory approximation. Uncertainty, however, can be shown to be present in the theoretical definition and practical approximation of an impact site; the theoretical justification for impact angle calculation; spatter bloodstain sample selection; the dimensional measurement of spatter bloodstain morphologies; the inability to fully incorporate droplet flight dynamics; and the limited numerical methods used to describe mathematical estimates. An experimental computer-based research design was developed to investigate this uncertainty. A series of experimental impact spatter patterns were created, and an exhaustive spatter bloodstain recording methodology developed and implemented. A computer application was developed providing a range of analytical approaches to the investigation of estimate uncertainty, including a three-dimensional computer graphic virtual investigative environment. The analytical computer application was used to generate a series of estimates using a broad spatter bloodstain sampling strategy, with six potentially probative estimates analysed in detail. Two additional pilot projects investigating the utility of a sampled photographic recording methodology and an automated image analysis approach to spatter bloodstain measurement were also conducted. The results of these analyses indicate that, with further development, the application of similar analytical approaches to the construction and investigation of an estimate could prove effective in minimising the effect that estimate uncertainty might have on informing the conclusions of this forensic reconstructive process, and thereby reaffirm the scientific expert evidential status of estimate techniques within legal contexts

A Logic-Based Framework for Web Access Control Policies

With the widespread use of web services, there is a need for adequate security and privacy support to protect the sensitive information these services could provide. As a result, there has been a great interest in access control policy languages which accommodate large, open, distributed and heterogeneous environments like the Web. XACML has emerged as a popular access control language, but because of its rich expressiveness and informal semantics, it suffers from a) a lack of understanding of its formal properties, and b) a lack of automated, compile-time services that can detect errors in expressive, distributed and heterogeneous policies. In this dissertation, I present a logic-based framework for XACML that addresses the above issues. One component of the framework is a Datalog-based mapping for XACML v3.0 that provides a theoretical foundation for the language, namely: a concise logic-based semantics and complexity results for full XACML and various fragments. Additionally, my mapping discovers close relationships between XACML and other logic based languages such as the Flexible Authorization Framework. The second component of this framework provides a practical foundation for static analysis of expressive XACML policies. The analysis services detect semantic errors or differences between policies before they are deployed. To provide these services, I present a mapping from XACML to the Web Ontology Language (OWL), which is the standardized language for representing the semantics of information on the Web. In particular, I focus on the OWL-DL sub-language, which is a logic-based fragment of OWL. Finally, to demonstrate the practicality of using OWL-DL reasoners as policy analyzers, I have implemented an OWL-based XACML analyzer and performed extensive empirical evaluation using both real world and synthetic policy sets

Automated Heuristic Generation By Intelligent Search

This thesis presents research that examines the effectiveness of several different program synthesis techniques when used to automate the creation of heuristics for a local search-based Boolean Satisfiability solver. Previous research focused on the automated creation of heuristics has almost exclusively relied on evolutionary computation techniques such as genetic programming to achieve its goal. In wider program synthesis research, there are many other techniques which can automate the creation of programs. However, little effort has been expended on utilising these alternate techniques in automated heuristic creation. In this thesis we analyse how three different program synthesis techniques perform when used to automatically create heuristics for our problem domain. These are genetic programming, exhaustive enumeration and a new technique called local search program synthesis. We show how genetic programming can create effective heuristics for our domain. By generating millions of heuristics, we demonstrate how exhaustive enumeration can create small, easily understandable and effective heuristics. Through an analysis of the memoized results from the exhaustive enumeration experiments, we then describe local search program synthesis, a program synthesis technique based on the minimum tree edit distance metric. Using the memoized results, we simulate local search program synthesis on our domain, and present evidence that suggests it is a viable technique for automatically creating heuristics. We then define the necessary algorithms required to use local search program synthesis without any reliance on memoized data. Through experimentation, we show how local search program synthesis can be used to create effective heuristics for our domain. We then identify examples of heuristics created that are of higher quality than those produced from other program synthesis methods. At certain points in this thesis, we perform a more detailed analysis on some of the heuristics created. Through this analysis, we show that, on certain problem instances, several of the heuristics have better performance than some state-of-the-art, hand-crafted heuristics

The Progressive Development and Post-failure Behaviour of Deep-seated Landslide Complexes

The concept of progressive shear surface development remains to be fully understood. This study aims to investigate the mechanisms of progressive shear surface development to failure, and the subsequent post-failure behaviour, of deep-seated landslide complexes. Field samples, collected from the Ventnor deep-seated landslide complex, Isle of Wight have been tested in a series of bespoke triaxial and back pressured shear box tests, in which field failure conditions are simulated by elevating pore water pressures under a constant deviator stress. These laboratory simulations have been calibrated with a detailed analysis of ground movement, groundwater and antecedent rainfall relationships from real-time site monitoring records from the site. A model to explain the progressive failure of landslides in cohesive materials is proposed. The model demonstrates that pre-failure movement in landslides occurs during the progressive shear surface development through the development of micro-cracks within the slope. This process is active during periods when porewater pressures are sufficiently elevated in the slope. These micro-cracks eventually lengthen and coalesce as stresses concentrate at micro-crack tips, leading to the development of a singular shear surface which is observed as tertiary creep. The study confirms that the onset of ‘Saito linearity’ in 1/v – t space is associated with this tertiary creep phase. This mechanism can occur through time dependent creep at constant stresses from below the peak strength envelope. The results have been validated against real-world landslide monitoring data to provide a new understanding of the shear surface mechanisms operating within the Ventnor landslide. The results contribute new knowledge regarding the mechanisms of shear surface development and provide an improved understanding of these mechanisms by developing one of the first high quality data sets that combines laboratory and field data. Finally, the study provides a new method to inform future landslide behaviour predictions for deep-seated slope failures

Study and design of topologies and components for high power density DC-DC converters

Size reduction of low power electronic DC–DC converters is a topic of major interest for power electronics which requires the study and design of circuits and components working under redefined requirements. For this purpose, novel circuital topologies provide advantages in terms of power density increment, especially where a single chip design is feasible. These concepts have been applied to design and implement an integrated high step-down multiphase buck converter and to study the miniaturization of a stackable fiflyback architecture. Particular attention has been dedicated to power inductors, focusing on the modeling and measurement of magnetic materials’ hysteresis and core losses

The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96

The NASA Goddard Space Flight Center (GSFC), the National Imagery and Mapping Agency (NIMA), and The Ohio State University (OSU) have collaborated to develop an improved spherical harmonic model of the Earth's gravitational potential to degree 360. The new model, Earth Gravitational Model 1996 (EGM96), incorporates improved surface gravity data, altimeter-derived gravity anomalies from ERS-1 and from the GEOSAT Geodetic Mission (GM), extensive satellite tracking data-including new data from Satellite Laser Ranging (SLR), the Global Postioning System (GPS), NASA's Tracking and Data Relay Satellite System (TDRSS), the French DORIS system, and the US Navy TRANET Doppler tracking system-as well as direct altimeter ranges from TOPEX/POSEIDON (T/P), ERS-1, and GEOSAT. The final solution blends a low-degree combination model to degree 70, a block-diagonal solution from degree 71 to 359, and a quadrature solution at degree 360. The model was used to compute geoid undulations accurate to better than one meter (with the exception of areas void of dense and accurate surface gravity data) and realize WGS84 as a true three-dimensional reference system. Additional results from the EGM96 solution include models of the dynamic ocean topography to degree 20 from T/P and ERS-1 together, and GEOSAT separately, and improved orbit determination for Earth-orbiting satellites

Magnetic steering of the ion beam in the Helicon Double Layer Thruster

Experiments are performed in the CHI KUNG plasma reactor to study the effect of introducing transverse components (aligned along the x-axis) to the cylindrically symmetric magnetic field (aligned along the z-axis) to produce magnetic steering of the ion beam in the Helicon Double Layer Thruster (HDLT). CHI KUNG is a cylindrical helicon plasma reactor, on which the first HDLT prototype is based, consisting of a 15 cm diameter, 31 cm long Pyrex source tube attached contiguously to a 32 cm diameter, 30 cm long aluminium diffusion chamber. Coaxially surrounding the source tube is an 18 cm long double saddle antenna connected to an L-matching network/generator system, fed with 13.56 MHz of radio-frequency power. Enclosing the source tube and antenna are two coaxial solenoids, referred to as the source and exit solenoids, which generate a diverging magnetic field. The peak magnetic field magnitudes produced by the source and exit solenoids are 132 G and 118 G, respectively, when a current of 3 A is flowing through each solenoid, pointing north into the diffusion chamber. Argon gas is fed in through the diffusion chamber and pumped to an operational pressure of 0.3 mTorr by a turbomolecular/rotary pumping system. Under these conditions, a double layer is formed ~ 5 cm inside the exit of the source tube, which accelerates a population of ions to form an ion beam that can be detected in the diffusion chamber. In this thesis, spatial measurement techniques are developed to measure the properties of the ion beam in the diffusion chamber, downstream of the double layer. Of particular interest is the ion beam density, and an analysis is developed to determine this parameter from the spatial data. Because the ion beam in the diffusion chamber is surrounded by ambient plasma, a retarding field energy analyzer (RFEA) is used to measure the flux of ions as a function of their energy, to separate the fast moving beam from the population of thermal background ions. A spatial map of the ion beam density can be obtained by sweeping the RFEA across the exit of the source tube at a number of different z{u00AC}axial positions, downstream of the double layer. As the ion beam travels into the diffusion chamber, a 5.70 {u00B1}0.4{u00B0} angle is observedbetween the ion beam reactor and the z-axis. This asymmetry has not before been observed in the largely cylindrically symmetric CHI KUNG reactor and the possible causes for this asymmetry are discussed. By introducing either one or two transverse solenoids to the CHI KUNG source region, asymmetric components of the magnetic field may be introduced and the resulting effect on the ion beam vector is observed. Experiments are broken up into two categories, with the effect of a single transverse solenoid initially investigated to demonstrate the phenomenon of magnetic steering in the HDLT. Subsequent experiments explore the use of an additional second transverse solenoid to better understand the magnetic steering phenomenon. The effect of varying the magnitude and polarity of the single transverse magnetic field (changing the solenoidal current) is observed to cause the ion beam to deflect away from the main axis (the z-axis), with larger transverse solenoidal currents resulting in greater angles of deflection. The direction of ion beam deviation is determined by the polarity of the transverse solenoid, with the ion beam deflecting in the direction of the transverse solenoid polarity. Deflection of the ion beam is measured up to -26.1{u00B0} {u00B1} 0.8{u00B0} and 13.5{u00B0} {u00B1} 0.7{u00B0} for single transverse solenoidal currents of 4 A north-out and 3 A north{u00AC}in, where north-out and north-in indicate the polarity of the transverse solenoid pointing in-to or out-of the source tube. Adding a second transverse solenoid, and orienting the two coaxial transverse solenoids in the same direction (in the negative x-direction) results in deflections of the ion beam for lower solenoidal currents. A current of 1.25 A flowing through both the transverse solenoids is observed to produce deflection of the ion beam up to 18.0{u00B0} {u00B1} 0.5{u00B0}, with the direction of deflection parallel to the transverse solenoidal polarity. By obtaining, for the first time, a spatial map of the ion beam downstream of a double layer in CHI KUNG, other properties of the ion beam can be obtained. The divergence of the ion beam is considered for a number of different measurement geometries and analyses, and reveals divergences similar to the more widely developed gridded ion engines. The experimental investigation of magnetic steering in the HDLT is uncommon in most electric thrusters, and the magnetic steering capabilities demonstrated in this thesis represent a significant advantage for the Helicon Double Layer Thruster as an alternative for electric propulsion missions