Doctor of Philosophy

dissertationThe study of the rheological properties and deposition potential of organic mixtures such as petroleum are explored below the initial wax appearance temperature using a recycled flow loop, an active slurry-making device called the Scraped Exchanger, and a model oil made with mineral oil, paraffin wax, and LVGO wax. Sub-WAT (heterogeneous) oils, when flowed under isothermal (ambient and oil temperatures are the same) and non-isothermal conditions exhibit no deposition and greatly reduced deposition when compared to similar thermal gradients in above-WAT (homogeneous) oils, respectively. Heterogeneous oils form gels during shutdown just as with homogeneous oils, but the gel strength is greatly reduced (>50%) even with very little precipitated material (oil temperature at shutdown just below WAT). Solids content at shutdown appears to show little effect on subsequent gel strength. Particle size distributions measured using CantyVision equipment at shutdown also show little to no effect on subsequent gel strength, suggesting a balance between particle size and particle count, as well as a fundamental difference in gel matrix structure compared to homogeneous gels. In the ranges tested, all heterogeneous gels exhibited cohesive ("center-core") failure manifested as breakage occurring first within the gel instead of at the walls. Breakage patterns explored using laser particle imaging velocimetry

Studies in Heterocyclic Chemistry and the Synthesis of 3-Methoxyflouranthene

Abstract Not Provided

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

The formation of cold air pools in valleys under stable conditions represents an important challenge for numerical weather prediction (NWP). The challenge is increased when the valleys that dominate cold pool formation are on scales unresolved by NWP models, which can lead to substantial local errors in temperature forecasts. In this study a 2-month simulation is presented using a nested model con- figuration with a finest horizontal grid spacing of 100 m. The simulation is compared with observations from the recent COLd air Pooling Experiment (COLPEX) project and the model’s ability to represent cold pool formation, and the surface energy balance is assessed. The results reveal a bias in the model long-wave radiation that results from the assumptions made about the sub-grid variability in humidity in the cloud parametrization scheme. The cloud scheme assumes relative humidity thresholds below 100 % to diagnose partial cloudiness, an approach common to schemes used in many other models. The biases in radiation, and resulting biases in screen temperature and cold pool properties are shown to be sensitive to the choice of critical relative humidity, suggesting that this is a key area that should be improved for very high-resolution modeling

A case‐study of cold‐air pool evolution in hilly terrain using field measurements from COLPEX

A case‐study investigation of cold‐air pool (CAP) evolution in hilly terrain is conducted using field measurements made during IOP 16 of the COLd‐air Pool EXperiment (COLPEX). COLPEX was designed to study cold‐air pooling in small‐scale valleys typical of the UK (∼100–200 m deep, ∼1 km wide). The synoptic conditions during IOP 16 are typical of those required for CAPs to form during the night, with high pressure, clear skies and low ambient winds. Initially a CAP forms around sunset and grows uninterrupted for several hours. However, starting 4 hr after sunset, a number of interruptions to this steady cooling rate occur. Three episodes are highlighted from the observations and the cause of disruption attributed to (a) wave activity, in the form of gravity waves and/or Kelvin–Helmholtz (KH) instability, (b) increases in the above‐valley winds resulting from the development of a nocturnal low‐level jet (NLLJ), (c) shear‐induced mixing resulting from instability of the NLLJ. A weakly stable residual layer provides the conditions for wave activity during Episode 1. This residual layer is eroded by a developing NLLJ from the top down during Episode 2. The sustained increase in winds at hill‐top levels – attributed to the NLLJ – continue to disrupt the CAP through Episode 3. Although cooling is interrupted, the CAP is never completely eroded during the night. Complete CAP break‐up occurs some 3.5 hr after local sunrise. This case‐study highlights a number of meteorological phenomena that can disrupt CAP evolution even in ideal CAP conditions. These processes are unlikely to be sufficiently represented by current operational weather forecast models and can be challenging even for high‐resolution research models

Evaluation of animal control measures on pet demographics in Santa Clara County, California, 1993–2006

The measurable benefits of animal control programs are unknown and the aim of this study was to determine the impact of these programs on pet population changes. A prospective cross-sectional study of 1000 households was implemented in 2005 to evaluate characteristics of the owned and unowned population of dogs and cats in Santa Clara County, California. The same population was previously studied 12 years earlier. During this time period, the county instituted in 1994 and then subsequently disestablished a municipal spay/neuter voucher program for cats. Dog intakes declined from 1992–2005, as they similarly did for an adjacent county (San Mateo). However, cat intakes declined significantly more in Santa Clara County than San Mateo, with an average annual decline of approximately 700 cats for the 12 year period. Time series analysis showed a greater than expected decline in the number of cats surrendered to shelters in Santa Clara County during the years the voucher program was in effect (1994–2005). The net savings to the county by reducing the number of cat shelter intakes was estimated at approximately $1.5 million. The measurable benefits of animal control programs are unknown and the aim of this study was to determine the impact of these programs on pet population changes

A short climatological study of cold air pools and drainage flows in small valleys

This paper uses detailed observations from the COLd air Pooling EXperiment (COLPEX) to study the frequency and characteristics of cold air pooling in a small-scale valley typical of much of the southern UK and other lowland regions of the world. The field experiment took place in and around the Clun Valley, Shropshire, England during July 2009-April 2010, which was a particularly cold winter with a record low in the NAO index. Cold pools, defined here as where the minimum valley temperature overnight is at least 1°C colder than the surrounding hill tops, occur on 45% of nights over the observational period, with strong cold pools (>4°C temperature difference) occurring on 12% of nights. As might be expected, cold pool formation is closely linked to conditions with clear skies and light winds, often associated with high pressure situations. Cold pools are also closely linked with weak down valley drainage flows. This contrasts with non-cold pool nights or daytime conditions where several other mechanisms also contribute to the observed winds in the valley. The data set highlights the importance of cold air pools and drainage flows, even in quite moderate terrain, and the impact this can have on local microclimates

Nyx-Net: Network Fuzzing with Incremental Snapshots

Coverage-guided fuzz testing (“fuzzing”) has become main- stream and we have observed lots of progress in this research area recently. However, it is still challenging to efficiently test network services with existing coverage-guided fuzzing methods. In this paper, we introduce the design and implementation of Nyx-Net, a novel snapshot-based fuzzing approach that can successfully fuzz a wide range of targets spanning servers, clients, games, and even Firefox’s Inter- Process Communication (IPC) interface. Compared to state- of-the-art methods, Nyx-Net improves test throughput by up to 300x and coverage found by up to 70%. Additionally, Nyx-Net is able to find crashes in two of ProFuzzBench’s targets that no other fuzzer found previously. When using Nyx-Net to play the game Super Mario, Nyx-Net shows speedups of 10-30x compared to existing work. Moreover, Nyx-Net is able to find previously unknown bugs in servers such as Lighttpd, clients such as MySQL client, and even Firefox’s IPC mechanism—demonstrating the strength and versatility of the proposed approach. Lastly, our prototype implementation was awarded a $20.000 bug bounty for enabling fuzzing on previously unfuzzable code in Firefox and solving a long-standing problem at Mozilla