David Tate

When goods persist in the marketplace over time, price indices can be computed directly from observed prices. Hedonic models are used to estimate real price growth for goods that do not persist in the marketplace long enough to establish a price change history. Hedonic models attempt to explain as much price change as possible using observable quality features. We describe challenges in developing a hedonic price index for military vehicles, and propose an alternative pseudo-hedonic model based on hypothesized unobservable quality growth within in vehicle families.

This practical book describes the basic science, clinical presentation and management of the 67 common acute medical presentations stipulated in the Royal College of Physicians syllabus for Core Medical Training and Acute Core Common Stem. • Case scenarios are included for each presentation, and guidance about management is offered in the context of national guidelines and important studies • Experienced clinicians describe their approach to common difficult problems and explain the answers to questions often asked on the ward round by successive generations of trainees • Chapters highlight key decisions that need to be made early, common misunderstandings, and risks • Detailed discussion provides an understanding of the rationale, allowing the reader to apply their knowledge to other situations • Guidance is provided on urgency of referral, safe ambulatory management, and when to seek specialist help. This is an essential resource that provides readers with the knowledge base to practise as a confident medical registrar.

One of the assumptions behind tactical mobile ad hoc networks (MANETs) is that routes consisting of multiple hops will be available to connect those nodes that lack line-of sight connectivity. The practical utility of MANET depends on this assumption being true and, for a mobile network, remaining true during mobility. In previous work, we showed that average node-to-node direct connectivity and the rate at which direct links break over time while moving through a given terrain can be characterized approximately using average terrain measures that are location and distance insensitive. Here, we exploit that result and extend our previous work to characterize the rate at which line-of-sight links and end-to-end shortest paths appear and disappear for mobile networks of various sizes in various terrains.

Terrain affects connectivity in mobile ad hoc networks (MANET). Both average pair wise link closure and the rate at which the link-state changes when nodes move depend on the characteristics of the intervening terrain. Even though these key parameters depend only mildly on inter node distances in common real-world terrains, empirical analysis finds that the number of connected components in the network and the probability of being fully-connected are not well-predicted by the average link probability in some terrains. This finding has implications for the limits of ad hoc connectivity under unconstrained maneuver.

Since the 1980s, the US military has been seeking a way to improve the ease and flexibility of communications within and between the Services. Forces deployed at that time used dozens of different radios, most of which could only communicate with other radios of the same type. Software Defined Radio (SDR) offered the promise of not only interoperating with all existing radios, but also allowing those legacy radios to communicate with each other. Just as important, SDR would enable future communications systems to be implemented on already-deployed hardware. This vision of interoperability and forward compatibility has not been realized, despite billions of dollars of investment in the Joint Tactical Radio System (JTRS). The authors reviewed JTRS program archives and studied the hardware and software architectures to determine whether there are fundamental technical reasons behind this failure. Our findings, which invoke the familiar trade off between performance and power consumption, are summarized in this paper. We identify three different architectural approaches used by the JTRS community over the years, and discuss why none has been able to realize the program's goals.

Terrain affects connectivity in mobile ad hoc networks (MANET). Both average pairwise link closure and the rate at which the link-state changes when nodes move depend on the characteristics of the intervening terrain. However, these key parameters depend only mildly on internode distances in common real-world terrains, which suggests that network performance in real terrains can be usefully modeled using simple time- and location-invariant average link-state probability and rate of change. We use this fact to predict the number of disconnected subnets at a random instant in a given terrain, and we compare these predictions against Monte Carlo sampling of node positions.