Approximate Models and Robust Decisions

Decisions based partly or solely on predictions from probabilistic models may be sensitive to model misspecification. Statisticians are taught from an early stage that "all models are wrong", but little formal guidance exists on how to assess the impact of model approximation on decision making, or how to proceed when optimal actions appear sensitive to model fidelity. This article presents an overview of recent developments across different disciplines to address this. We review diagnostic techniques, including graphical approaches and summary statistics, to help highlight decisions made through minimised expected loss that are sensitive to model misspecification. We then consider formal methods for decision making under model misspecification by quantifying stability of optimal actions to perturbations to the model within a neighbourhood of model space. This neighbourhood is defined in either one of two ways. Firstly, in a strong sense via an information (Kullback-Leibler) divergence around the approximating model. Or using a nonparametric model extension, again centred at the approximating model, in order to `average out' over possible misspecifications. This is presented in the context of recent work in the robust control, macroeconomics and financial mathematics literature. We adopt a Bayesian approach throughout although the methods are agnostic to this position

Factors Affecting Year 12 Retention Across Australian States and Territories in the 1990's

This paper contains a comparison of high school completion rates across Australian States and Territories from 1989 to 2002. These completion rates, known as 'retention rates', have a number of well-known deficiencies. When we adjust 'official' 2002 retention rates to take account of these measurement problems, the pattern of 'performance' across jurisdictions changes substantially. Moreover, the adjustments allow identification of the pattern of mismeasurement of national retention over the 1990s arising from the deficiencies of the retention rate calculation. We estimate that the retention rate was an especially poor measure of national school completion in the early 1990s, when it peaked. The peak in our adjusted retention measure during the early 1990s was less pronounced and the subsequent decline smaller than in the 'official' figures. Unlike those 'official' estimates, the adjusted measure of Year 12 retention was no lower in the late 1990s than it had been in the early 1990s.

A framework for assessing crop production from rotations

This report was presented at the UK Organic Research 2002 Conference of the Colloquium of Organic Researchers (COR). Organic farming systems rely on the management of biological cycles for the provision of nutrients, which are crucial to maximising the production from the system. Rotations based on the use of grass-legume leys are central to the concept of organic farming systems, because they have the potential to support both animal production, and a subsequent, exploitative, arable cropping phase. A major challenge in organic farming is managing the supply of nitrogen, since it has a key role in governing both productivity and environmental impact. Hence, within a rotational system, there is a need to understand the complex interactions that are occurring between crop species and management, livestock production system and the impact of soil and climate on these processes. To understand these interactions, a framework is being developed for rotational farming systems that describes the soil nitrogen, crop growth and livestock production. The framework must address questions that are relevant to researchers and extensions workers. Typical questions relate to the management of nutrients in the short and long-term. Additionally, there are concerns over the impact of weeds, pests and diseases on productivity, as well as the impact of adopting new strategies or crops on the farming system

Dynamic Real-time Verification of Program Call Flows

This disclosure describes a dynamic overlay that delineates control flows of an application to identify unexpected code execution pathways that may be indicative of a security breach. Identifying such unexpected (or unauthorized) execution pathways can enable their prevention. The overlay is generated by observing the control flow through the application to produce a histogram of probabilities from a first function call to subsequent function calls. Using the overlay enables the detection of attacks with higher fidelity and at a lower cost than existing approaches

Mechanism for Balancing of GPU Usage Between AI Queue Depth and Graphical Fidelity

Concurrent application demands that exceed available GPU resources can degrade performance and worsen the user experience. However, there are no easy mechanisms for lay users to tailor application performance and control GPU resource allocation. This disclosure describes techniques that enable users to specify preferences for prioritizing computational tasks performed via a GPU via conventional user interface mechanisms. Scheduling and switching workloads and batches of the requested computations on the GPU is performed according to user-specified preferences. Users can leverage the preference settings for managing performance tradeoffs between application functionality, balancing resource allocation when multitasking, troubleshooting potential GPU-related problems, etc. The techniques can enable users to save time and effort in troubleshooting GPU-related problems and can save manufacturers the cost of handling return and replacement of defective hardware

Authenticated Attribution of Media Content Bound to Devices

This disclosure describes techniques to authenticate that a media content item such as a photograph, a video, etc. is attributed to and originated by a particular user, based on the device on which the content was created. The content item is created on a device and associated with a digital signature using an attestation mechanism of the device such as trusted hardware or a sensor pattern that is unique to the device. The digital signature and content item are provided to a register or service for access by other users. When an accessing user views the content item, the content item is verified, via the digital signature, as having originated from the originating user’s device. The accessing user’s device displays the status of user attribution of the content item, indicating that the content item originates from a legitimate user and has not been forged, modified, or stolen. Described techniques are privacy-preserving and do not disclose the identity of the originating user

Renewable Student Projects: A Learning Strategy

Renewable course projects (i.e. projects whose lives extend beyond the end of an academic semester) provide an effective alternative to class assignments that require repetition of artificial tasks typical in many information systems and technology-related courses. Though these throwaway projects are certainly meritorious, renewable projects enable students to engage in real-world development paradigms, such as modularization and life cycles, to develop lasting systems that solve relevant problems. By embracing the full project life cycle, modularization of work, and open source software renewable projects expose students to traditional aspects of classroom development and also to the more real world features of the project cycle. Two case studies provide experiential evidence of the success of renewable projects

Climate Change in the Piscataqua/Great Bay Region: Past, Present, and Future

Earth ’s climate changes. It always has and always will. However, an extensive body of scientific evidence indicates that human activities are now a significant force driving change in the Earth’s climate system. This report describes how the climate of the Piscataqua/Great Bay region of coastal New Hampshire in the United States has changed over the past century and how the future climate of the region will be affected by human activities that are warming the planet. Overall, the region has been getting warmer and wetter over the last century, and the rate of change has increased over the last four decades. To generate future climate projections for the region, simulated temperature and precipitation from four general circulation models were fitted to local, long-term weather observations. Unknowns regarding future fossil fuel consumption were accounted for by using two future emissions scenarios. As greenhouse gases continue to accumulate in the atmosphere, temperatures will rise, extreme heat days are projected to occur more often and will be hotter, extreme cold temperatures are projected to occur less often, and cold days will be warmer.. Annual average precipitation is projected to increase 12 to 17% by end-of-century and the region can expect to see more extreme precipitation events in the future. Tidal gauge data indicates relative sea level at Portsmouth has risen 0.7 inches per decade over the past eight decades. Projected sea level rise of 1.7 to 6.3 feet will result in higher storm surges and more frequent flooding in coastal New Hampshire

Search for water in a super-Earth atmosphere: High-resolution optical spectroscopy of 55 Cancri e

We present the analysis of high-resolution optical spectra of four transits of 55Cnc e, a low-density, super-Earth that orbits a nearby Sun-like star in under 18 hours. The inferred bulk density of the planet implies a substantial envelope, which, according to mass-radius relationships, could be either a low-mass extended or a high-mass compact atmosphere. Our observations investigate the latter scenario, with water as the dominant species. We take advantage of the Doppler cross-correlation technique, high-spectral resolution and the large wavelength coverage of our observations to search for the signature of thousands of optical water absorption lines. Using our observations with HDS on the Subaru telescope and ESPaDOnS on the Canada-France-Hawaii Telescope, we are able to place a 3-sigma lower limit of 10 g/mol on the mean-molecular weight of 55Cnc e's water-rich (volume mixing ratio >10%), optically-thin atmosphere, which corresponds to an atmospheric scale-height of ~80 km. Our study marks the first high-spectral resolution search for water in a super-Earth atmosphere and demonstrates that it is possible to recover known water-vapour absorption signals, in a nearby super-Earth atmosphere, using high-resolution transit spectroscopy with current ground-based instruments.Comment: Accepted for publication in ApJ 12 pages, 9 figures. Email: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]