Using learned action models in execution monitoring

Planners reason with abstracted models of the behaviours they use to construct plans. When plans are turned into the instructions that drive an executive, the real behaviours interacting with the unpredictable uncertainties of the environment can lead to failure. One of the challenges for intelligent autonomy is to recognise when the actual execution of a behaviour has diverged so far from the expected behaviour that it can be considered to be a failure. In this paper we present further developments of the work described in (Fox et al. 2006), where models of behaviours were learned as Hidden Markov Models. Execution of behaviours is monitored by tracking the most likely trajectory through such a learned model, while possible failures in execution are identified as deviations from common patterns of trajectories within the learned models. We present results for our experiments with a model learned for a robot behaviour

The identification and exploitation of almost symmetry in planning problems

Previous work in symmetry detection for planning has identified symmetries between domain objects and shown how the exploitation of this information can help reduce search at plan time. However these methods are unable to detect symmetries between objects that are almost symmetrical: where the objects must start (or end) in slightly different configurations but for much of the plan their behaviour is equivalent. In the paper we outline a method for identifying such symmetries and discuss how this symmetry information can be positively exploited to help direct search during planning we have implemented this method and integrated it with the FF-v2.3 planner and in the paper we present results of experiments with this approach that demonstrate its potential

Abstraction-based action ordering in planning

Many planning problems contain collections of symmetric objects, actions and structures which render them difficult to solve efficiently. It has been shown that the detection and exploitation of symmetric structure in planning problems can dramatically reduce the size of the search space and the time taken to find a solution. We present the idea of using an abstraction of the problem domain to reveal symmetric structure and guide the navigation of the search space. We show that this is effective even in domains in which there is little accessible symmetric structure available for pruning. Proactive exploitation represents a flexible and powerfulalternative to the symmetry-breaking strategies exploited in earlier work in planning and CSPs. The notion of almost symmetry is defined and results are presented showing that proactive exploitation of almost symmetry can improve the performance of a heuristic forward search planner

Single and Many Particle Correlation Functions and Uniform Phase Bases for Strongly Correlated Systems

The need for suitable many or infinite fermion correlation functions to describe some low dimensional strongly correlated systems is discussed. This is linked to the need for a correlated basis, in which the ground state may be postive definite, and in which single particle correlations may suffice. A particular trial basis is proposed, and applied to a certain quasi-1D model. The model is a strip of the 2D square lattice wrapped around a cylinder, and is related to the ladder geometries, but with periodic instead of open boundary conditions along the edges. Analysis involves a novel mean-field approach and exact diagonalisation. The model has a paramagnetic region and a Nagaoka ferromagnetic region. The proposed basis is well suited to the model, and single particle correlations in it have power law decay for the paramagnet, where the charge motion is qualitatively hard core bosonic. The mean field also leads to a BCS-type model with single particle long range order.Comment: 23 pages, in plain tex, 12 Postscript figures included. Accepted for publication in J.Physics : Condensed Matte

Quality of Life Following Massive Weight Loss and Body Contouring Surgery: an Exploratory Study.

Reconstructive surgery is a major growth intervention for body improvement, enhancing appearance and psychological well-being following massive weight loss. The psychosocial benefits include greater capacity for social networking, lower scores of body uneasiness, body image satisfaction, improved mental well-being and physical function. However little collective evidence exists regarding the impact of body contouring on patients Quality of Life (QoL) and there is a lack of systematic review and randomised controlled trials (RCTs) with a scarcity of high level evidence. The purpose of this exploratory study was to explore the QoL perceptions, experiences and outcomes of patients who have undergone body contouring following significant weight loss and to explore the relevance and potential utility of the Obesity Psychosocial State Questionnaire (OPSQ) as a valuable QoL outcomes measuring tool for use in clinical research. Data were collected in a community setting in the south of England via digitally recorded semi-structured interviews with twenty participants (18 women and 2 men), who also self-completed the Obesity Psychosocial State Questionnaire (OBSQ). Medical notes were reviewed retrospectively to gather data about body mass index (BMI), co-morbidities, eating profiles/lifestyle, uptake of bariatric surgery and type/number of body contouring procedures undergone. A thematic approach was adopted to analyse the interviews and medical record data, supported by Nvivo7 qualitative software, and a statistical approach to analyse the questionnaire data, supported by Statistical Analysis Software. The results provide unique glimpses of the body contouring interventions for empowering and facilitating a ‘transformation’, a ‘new identity’, a ‘new start’ in life, improved physical function, greater body image satisfaction, a stronger sense of well-being and an improved quality of life. A few of the participants who reported that their weight gain was powered by childhood traumas (abuse, neglect, abandonment) continued to struggle for ‘normality’, with fragile eating control and addictive traits. Eating disordered trauma survivors mentioned post traumatic flashbacks and underlying conflicts that triggered powerlessness and emotional eating. The emotional flooding with psychological and body related memories did not appear to be fully processed or released, despite counselling and binge eating programmes. The participants also confirmed the value of the OBSQ, whilst highlighting its limited set of three questions on feelings of self-efficacy towards eating habits. The study findings show that body contouring optimises quality of life with significant improvement in physical function, body image, mental health and psychosocial function. Further research is warranted to extent the scope of the findings within a sample drawn from multiple treatment centres. This would valuably: • Explore gender, ethnic and cultural variables, important to optimising quality of life. • Clarify distinguishing features between short and long-term QoL outcomes. • Lead to the development of national policy and guidelines on reconstructive ‘body contouring’ surgery following massive weight loss, in line with the call from the British Association for Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) A future multi-centre collaborative study could employ the OBSQ, supplemented by an additional tool to explore factors that influence eating habits such as the three factor eating questionnaire (such as the TFEQ-R1 21 Scale). Such research could enhance understanding of quality of life and long-term weight management

Killing Spinors for the Bosonic String

We obtain the effective action for the bosonic string with arbitrary Yang-Mills fields, up to the \alpha' order, in general dimensions. The form of the action is determined by the requirement that the action admit well-defined Killing spinor equations, whose projected integrability conditions give rise to the full set of equations of motion. The success of the construction suggests that the hidden "pseudo-supersymmetry" associated with the Killing spinor equations may be a property of the bosonic string itself.Comment: 9 page