A nonlinear filtering approach to changepoint detection problems:direct and differentialg-geometric methods

A benchmark change detection problem is considered which involves the detection of a change of unknown size at an unknown time. Both unknown quantities are modelled by stochastic variables, which allows the problem to be formulated within a Bayesian framework. It turns out that the resulting nonlinear filtering problem is much harder than the well-known detection problem for known sizes of the change, and in particular that it can no longer be solved in a recursive manner. An approximating recursive filter is therefore proposed, which is designed using differential-geometric methods in a suitably chosen space of unnormalized probability densities. The new nonlinear filter can be interpreted as an adaptive version of the celebrated Shiryayev-Wonham equation for the detection of a priori known changes, combined with a modified Kalman filter structure to generate estimates of the unknown size of the change. This intuitively appealing interpretation of the nonlinear filter and its excellent performance in simulation studies indicate that it may be of practical use in realistic change detection problems

Exploring vague language use and voice variation in human-agent interaction

This thesis addresses the linguistic phenomenon of vague language (VL) and its effect on the creation of identity in the emerging and developing field of human-agent interaction (HAI). Current research on VL has focused on human interaction, while similar existing literature on language in HAI has focused on politeness theory and facework. This thesis brings the two research fields together and uses them as a focusing lens to investigate the issue of identity in agents – software with varying degrees of autonomy and intelligence. Agents are increasingly common in our everyday lives, particularly in the role of an instructor. Intelligent personal assistants are a frequent feature on smartphones, automated checkout systems pervade supermarkets both large and small, and satellite navigation systems have been a mainstay for over a decade now. Despite their frequency, there is relatively little research into the communication challenges surrounding HAI. Much like other people, the language and voice of agents have the ability to affect our perceptions and of them, and shape the way in which we create their identities. Instruction giving, amongst other facets of talk, in human communication can be mitigated through the use of VL. This can reduce the imposition we have on interaction partners, pay respect to a listener’s face, and establish and maintain a positive rapport with our interlocutors. This can have a profound effect on the desire to interact with someone again. Furthermore, agents that use speech to communicate are assigned one of two varieties of voice – synthesised or pre-recorded human speech, both of which have documented benefits and drawbacks. Given the rise of agents in the modern world, it is in the best interest of all parties to understand the salient variables that affect our perceptions of agents, and what effect VL and other variables such as voice in language and voice may have in our interactions with them. This thesis provides a novel approach to investigating both VL and voice in HAI. A general framework is presented with the use of a specific VL model to apply in the interactions, which is designed around verbal agents giving people instructions on how to construct Lego models. The first study compares the effects of a vague and non-vague verbal agent in this context, while the second study focuses on the comparative use of synthesised text-to-speech voices and professional human recordings in the same context. The results from the investigation reveal key findings regarding the use of VL in a verbal agent instructive context. The first study indicated that a synthesised agent voice is better suited to using non-vague instructions, while the second study revealed that a professional voice actor is a preferable candidate for using VL in comparison to two different synthesised voices. These findings discuss the issue of identities in HAI. They reveal that, when an agent instructor is perceived to have a voice that is non-human and machinelike, it is more likely that its use of VL will be received less positively. This is often because the combination of voice and language do not mix, but is also a result of a clash of perceived group identities between agent and human speech. As agents are typically direct, the use of “humanlike” VL can create a large disparity between a person’s expectations of agent speech and the reality of the interaction. Similarly, if an agent’s voice has more of a humanlike feel to it, then its use of VL will create less disparity and has the potential to bridge the gap between these two group identities. This poses discussions on the nature of agent identity and how it compares to those in humans. The thesis concludes with reflection on the findings in light of existing linguistic theories, and how further research into this field may assist agent designers, researchers, and agent users alike. A suggestion of employing a corpus linguistics approach to HAI is proposed, which may pave the way for future success in this area

Sulfur Mineralogy at the Mars Phoenix Landing Site

The Mars Phoenix Scout mission landed at the northernmost location (approx.68deg N) of any lander or rover on the martian surface. This paper compares the S mineralogy at the Phoenix landing site with S mineralogy of soils studied by previous Mars landers. S-bearing phases were not directly detected by the payload onboard the Phoenix spacecraft. Our objective is to derive the possible mineralogy of S-bearing phases at the Phoenix landing site based upon Phoenix measurements in combination with orbital measurements, terrestrial analog and Martian meteorite studies, and telescopic observations

Marine reserve effects on fishery profit

Some studies suggest that fishery yields can be higher with reserves than under conventional management. However, the economic performance of fisheries depends on economic profit, not fish yield. The predictions of higher yields with reserves rely on intensive fishing pressures between reserves; the exorbitant costs of harvesting low-density populations erode profits. We incorporated this effect into a bioeconomic model to evaluate the economic performance of reserve-based management. Our results indicate that reserves can still benefit fisheries, even those targeting species that are expensive to harvest. However, in contrast to studies focused on yield, only a moderate proportion of the coast in reserves (with moderate harvest pressures outside reserves) is required to maximize profit. Furthermore, reserve area and harvest intensity can be traded off with little impact on profits, allowing for management flexibility while still providing higher profit than attainable under conventional management

Recent advance in high manufacturing readiness level and high temperature CMOS mixed-signal integrated circuits on silicon carbide

A high manufacturing readiness level silicon carbide (SiC) CMOS technology is presented. The unique process flow enables the monolithic integration of pMOS and nMOS transistors with passive circuit elements capable of operation at temperatures of 300 °C and beyond. Critical to this functionality is the behaviour of the gate dielectric and data for high temperature capacitance–voltage measurements are reported for SiO2/4H-SiC (n and p type) MOS structures. In addition, a summary of the long term reliability for a range of structures including contact chains to both n-type and p-type SiC, as well as simple logic circuits is presented, showing function after 2000 h at 300 °C. Circuit data is also presented for the performance of digital logic devices, a 4 to 1 analogue multiplexer and a configurable timer operating over a wide temperature range. A high temperature micro-oven system has been utilised to enable the high temperature testing and stressing of units assembled in ceramic dual in line packages, including a high temperature small form-factor SiC based bridge leg power module prototype, operated for over 1000 h at 300 °C. The data presented show that SiC CMOS is a key enabling technology in high temperature integrated circuit design. In particular it provides the ability to realise sensor interface circuits capable of operating above 300 °C, accommodate shifts in key parameters enabling deployment in applications including automotive, aerospace and deep well drilling

Game Theoretical Interactions of Moving Agents

Game theory has been one of the most successful quantitative concepts to describe social interactions, their strategical aspects, and outcomes. Among the payoff matrix quantifying the result of a social interaction, the interaction conditions have been varied, such as the number of repeated interactions, the number of interaction partners, the possibility to punish defective behavior etc. While an extension to spatial interactions has been considered early on such as in the "game of life", recent studies have focussed on effects of the structure of social interaction networks. However, the possibility of individuals to move and, thereby, evade areas with a high level of defection, and to seek areas with a high level of cooperation, has not been fully explored so far. This contribution presents a model combining game theoretical interactions with success-driven motion in space, and studies the consequences that this may have for the degree of cooperation and the spatio-temporal dynamics in the population. It is demonstrated that the combination of game theoretical interactions with motion gives rise to many self-organized behavioral patterns on an aggregate level, which can explain a variety of empirically observed social behaviors

Extent and retreat history of the Barra Fan Ice Stream offshore western Scotland and northern Ireland during the last glaciation

During the Last Glacial Maximum (LGM) the marine-terminating Barra Fan Ice Stream (BFIS), a major conduit of the British Irish Ice Sheet (BIIS), drained much of western Scotland and northwest Ireland with ice streaming onto the continental shelf of the Malin Sea. The extent and retreat history of this ice stream across the shelf, until now, is not well known. In particular, geochronological constraints on the history of this ice stream have thus far been restricted to deep-sea cores or terrestrial cosmogenic nuclide dating onshore, with ages across the shelf absent. To understand the possible external forcing factors acting on this marine terminating ice stream during retreat, improved geochronological constraint on its deglaciation is necessary. Here, we present new geophysical data, marine sediment cores and over forty radiocarbon dates to provide important constraints on maximum extent of the BFIS, as well as the timing and pattern of retreat back across the Malin Shelf. Dated moraines and grounding-zone wedges (GZW) seen in seafloor sub-bottom profiles provide evidence that the BFIS reached the Malin Shelf edge during the LGM and was at its maximum extent around 26.7 ka BP. The presence of two sets of GZWs suggests that the style of retreat was episodic. The new radiocarbon chronology shows that retreat from the shelf edge was underway by 25.9 ka BP, with the majority of the continental shelf ice free by 23.2 ka BP, and that glacimarine conditions were present in the Sea of Hebrides by 20.2 ka BP at the latest. Collectively, these results indicate that the majority of the Malin Shelf was free of grounded ice by ∼21.5–20 ka BP, which is up to 4000 years earlier than previously reconstructed. We attribute this early deglaciation to high relative sea level caused by glacial isostatic depression when the BIIS reached its maximum extent promoting ice shelf and grounding line instability. Two deep troughs, forming reverse bed slopes, aided the continued retreat of the BFIS. This suggests that local ice loading and bed morphology can be significant controls on the destabilisation of a marine-terminating ice stream and can override the influence of ocean and atmospheric temperatures

Pion-Muon Asymmetry Revisited

Long ago an unexpected and unexplainable phenomena was observed. The distribution of muons from positive pion decay at rest was anisotropic with an excess in the backward direction relative to the direction of the proton beam from which the pions were created. Although this effect was observed by several different groups with pions produced by different means, the result was not accepted by the physics community, because it is in direct conflict with a large set of other experiments indicating that the pion is a pseudoscalar particle. It is possible to satisfy both sets of experiments if helicity-zero vector particles exist and the pion is such a particle. Helicity-zero vector particles have direction but no net spin. For the neutral pion to be a vector particle requires an additional modification to conventional theory as discussed herein. An experiment is proposed which can prove that the asymmetry in the distribution of muons from pion decay is a genuine physical effect because the asymmetry can be modified in a controllable manner. A positive result will also prove that the pion is NOT a pseudoscalar particle.Comment: 9 pages, 3 figure

Probing Heavy Higgs Boson Models with a TeV Linear Collider

The last years have seen a great development in our understanding of particle physics at the weak scale. Precision electroweak observables have played a key role in this process and their values are consistent, within the Standard Model interpretation, with a light Higgs boson with mass lower than about 200 GeV. If new physics were responsible for the mechanism of electroweak symmetry breaking, there would, quite generally, be modifications to this prediction induced by the non-standard contributions to the precision electroweak observables. In this article, we analyze the experimental signatures of a heavy Higgs boson at linear colliders. We show that a linear collider, with center of mass energy \sqrt{s} <= 1 TeV, would be very useful to probe the basic ingredients of well motivated heavy Higgs boson models: a relatively heavy SM-like Higgs, together with either extra scalar or fermionic degrees of freedom, or with the mixing of the third generation quarks with non-standard heavy quark modes.Comment: 21 page