Showing papers by "William Whittaker published in 2015"

The impact of paying treatment providers for outcomes: difference-in-differences analysis of the ‘payment by results for drugs recovery’ pilot

Abstract: Aims: To estimate the effect on drug misuse treatment completion of a pilot scheme to pay service providers according to rates of recovery. Design: A controlled, quasi-experimental (difference-in-differences) observational study using multi-level random effects logistic regression. Setting: Drug misuse treatment providers in all 149 commissioning areas in England in the financial years 2011–12 and 2012–13. Participants: Service users treated in England in 2011–12 and 2012–13. Intervention and comparators: Linkage of provider payments to performance indicators in eight pilot commissioning areas in England compared with all 141 non-pilot commissioning areas in England. Measurements: Recovery was measured by successful completion of treatment (free from drugs of dependence) and engagement with services was measured by rates of declining to continue with treatment. Findings: Following the introduction of the pilot scheme, service users treated in pilot areas were 1.3 percentage points [odds ratio (OR) = 0.859; 95% confidence interval (CI) = 0.788, 0.937] less likely to complete treatment compared with those treated in comparison areas. Service users treated in pilot areas were 0.9 percentage points (OR = 2.934; 95% CI = 2.094, 4.113) more likely to decline to continue with treatment compared with those treated in comparison areas. Conclusions: In the first year of the pilot ‘Payment by Results for Drugs Recovery’ scheme in England, linking payments to outcomes reduced the probability of completing drug misuse treatment and increased the proportion service users declining to continue with treatment.

Terrain traversability prediction by imaging thermal transients

Abstract: The inability of current robotic perception techniques to adequately detect non-geometric terrain hazards is a primary cause of failure for robots operating in natural terrain on Mars, the Moon, and Earth. Classical approaches detect surface appearance but do not measure the underlying mechanical properties that determine wheel-terrain interaction. Diurnal temperature variations of a granular material, however, are strongly correlated with both its surface appearance and subsurface geophysical properties. This paper presents a technique for determining relative differences in looseness and traversability of granular terrain through analysis of thermal imagery. Terrain compaction and traversability are predicted by estimating a material's thermal inertia from observations of thermal transients. Results from a set of experiments in sandy terrain demonstrate the ability of this approach to differentiate between safe, compact and hazardous, loose terrain.

Predicting Terrain Traversability from Thermal Diffusivity

Abstract: This paper presents a method to predict soil traversability by estimating the thermal diffusivity of terrain using a moving, continuous-wave laser. This method differentiates between different densities of the samematerial, which visionbased methods alone cannot achieve. The bulk density of a granular material has a significant effect on both its mechanical behavior and its thermal properties. This approach fits the thermal response as effected by a laser to an analytical model that is dependent on thermal diffusivity. Experimental soil strength measurements validate that thermal diffusivity is a predictor of traversability for a given material.

Planning routes of continuous illumination and traversable slope using connected component analysis

Abstract: This paper presents a method that applies connected component analysis to plan routes that keep robots continuously illuminated and on traversable slopes while reaching one or more goal locations Such routes promise to extend the lifespan, range, and scientific return of solar-powered robots exploring environments with changing but predictable lighting conditions, particularly those of the Moon and Mercury Maps of lighting and ground slope that describe these constraints in position and time are computed, and all distinct interconnected regions that have both direct sunlight and safe slope are found using connected component analysis These three-dimensional connected components are pruned of roots that violate time constraints and branches that dead-end in discontinuous routes Each component is the basis for a graph that includes all feasible routes from the initial time to the final time of that component The shortest feasible route between a pair of start and goal positions within the same component is found using A* search and is characterized by its total length and average speed Malapert Peak and Shackleton Crater, both near the Moon's South Pole, serve as examples throughout this paper due to their highly-relevant, dynamic, and predictable lighting caused by the Moon's motion relative to the Sun

Measuring the Impacts of Health Conditions on Work Incapacity – Evidence from the British Household Panel Survey

Abstract: The UK has experienced substantial increases in both the number of claimants of work incapacity benefit and the proportion of claims for mental health reasons. However, identifying causality between experiencing mental health problems and claiming benefits is complex as claiming disability benefits may be the instigator or result of having a mental health problem. We use longitudinal data from the British Household Panel Survey (1991–2008) to disentangle the relationship between claiming benefits and mental health problems. We model the probability of claiming disability benefits using a dynamic random-effects probit model, which reduces the endogeneity bias in modelling the effects of health on claiming disability benefits. Mental health has the largest effect of all health conditions modelled on the probability of disability benefit claiming. We find that the causal effect of mental health on claiming disability benefits is substantially over-estimated by cross-sectional associations. The effect decreases in magnitude from 12.5 to 0.5 percentage points for males and 8 to 0.7 percentage points for females. Policymakers should pay attention to other important influences on claiming disability benefits as well as interventions to improve the health of the working-age population.

Planning views to model planetary pits under transient illumination

Abstract: This paper addresses the problem of planning views for modeling large, local, substantially 3D terrain features at long range from surface rovers. These include building-size and stadium size pits with vertical walls. Pits have been identified in recent high-resolution images of the Moon and Mars. Planetary pits are interesting scientific targets created by collapse, often exposing layers of bare rock in their walls, hinting at past volcanism and other subsurface processes with their morphology. Some offer glimpses into caves. This paper presents a pipeline for view trajectory planning that enables detailed modeling of planetary pits from surface rovers. Techniques for converting prior terrain knowledge into a planning problem are developed, methods for planning rover images are discussed, and a comparison of different image-based reconstruction methods for pit modeling is presented. Results from preliminary field experiments for the end-to-end view trajectory planning pipeline are presented.

Estimating the wider societal benefits of changes in health

Abstract: There is renewed interest in the wider societal benefits of health interventions. Estimation of these effects should relate to changes in health rather than cross-sectional differences. We consider the impact of health on net State contributions, which include contributions to tax revenues and receipt of benefits. We subject cross-sectional differences in net contributions across health states to a more rigorous longitudinal analysis using the 1991-2008 British Household Panel Survey. We estimate the effects of 12 self-reported health problems on tax contributions and benefits received, controlling for several confounding factors and individual heterogeneity. We find cross-sectional differences in tax contributions and benefit receipts are substantially larger than those associated with changes in health. Changes in depression have the largest impact on net contributions. Estimates of net resource contributions should be based on longitudinal analysis to avoid overstating the wider societal benefits of health interventions.

Flyover Modeling of Planetary Pits

Abstract: Introduction: On the surface of the moon and Mars there are hundreds of skylights, which are collapsed holes that are believed to lead to underground caves. This research uses Vision, Inertial, and LIDAR sensors to build a high resolution model of a skylight as a landing vehicle flies overhead. We design and fabricate a pit modeling instrument to accomplish this task, implement software, and demonstrate sensing and modeling capability on a suborbital reusable launch vehicle flying over a simulated pit. Future manned colonies on other planets and moons will start in caves for their protection from the harsh space environment, led by the technology developed by this research. While planetary caves have been hypothesized for decades, they have not been plausible exploration candidates due to lack of surface access, difficulty of operation, and obscurity from orbit. Newly discovered planetary pits might be key to accessing subsurface voids, caves, and lava tubes. While the existence of pits is now unambiguous, how to explore them and whether any lead to extended caves is unknown. Pits represent an unparalleled opportunity to access enigmatic subterranean spaces, but their complex geometry makes them impossible to fully observe from orbit. Future robotic exploration missions will target one of these pits[3]. As a spacecraft is about to land, it flies at an altitude under a few hundred meters, traveling at a speed under tens of meters per second. As it flies over a pit during this time, it can collect high quality visual, inertial, and LIDAR data at unprecedented viewing angles from which to model the pit. This same sensor suite is used for precision navigation and terrain hazard avoidance. Reconnaissance from flyover modeling will be used to inform approach and entry paths for rovers[4]. It will be used to characterize geology, select likely locations for inhabitation, and inform follow on exploration. Instrument Design: The pit modeling instrument design accounts for pit geometry, vehicle dynamics during scanning, and required data precision and resolution. The geometry of planetary skylights drives range and field of view of the sensors. Our work specifically studied lunar skylights, which are the best characterized and of high interest. Wagner and Robinson[5] used automated computer vision to detect 200 candidate skylights that are evenly distributed in both location and size. Based on these statistics, the sensor is designed to survey an area that is nominally 50m in radius and 50m in depth. This can model the majority of lunar pits. The dynamical parameters of the landing phase determine sensor range and rate requirements. One example with publicly available data is the NASA ALHAT free flight campaigns on the Morpheus vehicle, which commanded an apogee of 245 meters and a 30-degree glide slope at 12.5 meters per second[1]. This trajectory has been designed to simulate the final landing portion of a robotic lunar mission and can be used as the nominal profile for a skylight scanning mission. From this nominal trajectory, we defined the maximum sensing range to be 260m. This is corresponds to a 45 degree pointing angle above vertical at 180m altitude.