An overview of link-level measurement techniques for wide-area wireless networks

By building wireless link-level measurement tools we hope to improvement the design, deployment and management of wide-area wireless community networks. This paper identifies existing link-level measurement techniques and discusses the advantages and disadvantages of each in the context of measuring and monitoring such networks. Finally, we make a case for the need for more sophisticated techniques and tools which will assist both day-to-day network operations as well as wireless network research

Rail Track Maintenance Planning: An Assessment Model

In Australia, railway track maintenance costs comprise between 25-35 percent of total freight train operating costs. Track maintenance planning models have been shown to reduce maintenance costs by 5 to 10 percent though improved planning. This paper describes a model which has been developed to deal with the track maintenance planning function at the medium to long-term levels. This model simulates the impacts of degrading railway track conditions and related maintenance work, in contrast to tradition models that mainly use expert systems. The model simulates the degrading track condition using an existing track degradation model. Track condition data from that model is used to determine if safety related speed restrictions are needed and what immediate maintenance work may be required for safe train operations. The model outputs the net present value of the benefits of undertaking a given maintenance strategy, when compared with a base-case scenario. The model approach has advantages over current models in investigating what if scenarios. The track engineer can assess the possible benefits in reduced operating costs from upgrading track infrastructure or from the use of improved maintenance equipment. After describing the model inputs and the assumptions used, the paper deals with the simulation of track maintenance and of train operating costs over time. The results of applying the model to a test track section using a number of different maintenance strategies are also given

The Evolution of E-Inclusion: Technology in Education for the Vision-Impaired

The 1970s and 1980s saw a rapid take-up in the use of personal computers. During the same time period, society began to move towards providing equity for people with disabilities. As legislators around the world created new disability and Information Technology policies, more people with disabilities were given access to education and the evolving computing tools provided unprecedented educational opportunities. These opportunities were due to the use of new technologies such as outputting of electronic text to voice synthesizers. The provision of assistive technology was not only helpful; it also provided education through a medium that was previously unavailable, particular to the blind and vision impaired. For much of the 1980s the development of text-processing sensory technologies, connected to personal computers, led to a closer equality between the educational services of the able-bodied and people with disabilities. Unfortunately this evolution as not without notable difficulties: issues surrounding the cost of products, the lack of support from large corporations and choice of platform resulted in substantial difficulties for educators in the assessment of appropriate technology. In addition, many of these products became largely redundant in the late-1980s as corporations began to place more emphasis on the Graphical User Interface (GUI). Although the GUI was remarkably successful in allowing the general public to gain better access to personal computing, it’s non-text nature once again caused a digital divide for people with disabilities. Although it is clear that the evolution of the personal computer has had a significant impact on the provision of education for people with disabilities, this paper highlights the historical repetition where innovation is prioritized above e-inclusion

More effective social services

In June 2014, the Productivity Commission was asked to look at ways to improve how government agencies commission and purchase social services. The final report was released in mid-September 2015. It makes several recommendations about how to make social services more responsive, client-focused, accountable and innovative. The final inquiry report has two key messages. First, system-wide improvement can be achieved and should be pursued. Second, New Zealand needs better ways to join up services for those with multiple, complex needs. Capable clients should be empowered with more control over the services they receive. Those less capable need close support and a response tailored to their needs, without arbitrary distinctions between services and funds divided into “health”, “education”, etc. These are significant, but extremely worthwhile, changes for New Zealand

Migrating Planets

A planet orbiting in a disk of planetesimals can experience an instability in which it migrates to smaller orbital radii. Resonant interactions between the planet and planetesimals remove angular momentum from the planetesimals, increasing their eccentricities. Subsequently, the planetesimals either collide with or are ejected by the planet, reducing the semimajor axis of the planet. If the surface density of planetesimals exceeds a critical value, corresponding to 0.03 solar masses of gas inside the orbit of Jupiter, the planet will migrate inward a large distance. This instability may explain the presence of Jupiter-mass objects in small orbits around nearby stars.Comment: Latex, 14 pages, and 2 postscript figures. Appeared in Science, 2 January; Table 1 originally omitte

BIOFUELS, CLIMATE POLICY, AND WATER MANAGEMENT: ASSESSING POLICY-INDUCED SHIFTS ON AGRICULTURE’S EXTENSIVE AND INTENSIVE MARGINS

Biofuel expansion efforts and climate mitigation policy could fundamentally alter land management trends in U.S. agriculture and forestry (AF) by mandating biofuel feedstock production and providing incentives for greenhouse gas (GHG) emissions reduction and carbon sequestration from terrestrial sources. Research has shown that biofuel expansion can alter commodity markets, induce agricultural land expansion, and intensify production. Meanwhile, GHG mitigation efforts could limit agricultural expansion, reduce current cultivation, and lower management intensity by incentivizing GHG emissions reduction and carbon sequestration within AF. To date, little work has attempted to quantify biofuel and climate policy-induced shifts together along the extensive and intensive agricultural production margins within a systems-based framework, though such shifts could have resounding implications on agricultural water consumption and quality. This study uses a comprehensive and detailed economic model of the U.S. AF sectors to simulate land management responses to biofuel expansion and GHG policies. While bioenergy production and altered AF management practices are found to significantly reduce GHG emissions, additional water consumption and nutrient use are possible policy outcomes. Specifically, we find that policies that influence shifts to the extensive margin will increase aggregate water use and nutrient application, but lead to lower intensity per-unit area. Conversely, when combined with biofuel mandates climate mitigation incentives lower agricultural land expansion, but lead to higher levels of management intensity. Somewhat contrary to expectations, GHG mitigation incentives cause water and nutrient use intensity to grow at an increasing rate due to the greater level of land use competition. Additionally, important regional trends emerge, as water use and quality concerns grow with the CO2 price in areas with limited GHG mitigation possibilities. This suggests that “water leakage” is possible whereby emissions reduction activities decrease output in one region and stimulate management intensity elsewhere. The potential indirect consequences of combined biofuel and climate mitigation incentives on water resource systems warrant further attention in policy design and future research.Greenhouse gas mitigation, biofuels, water resource management, Environmental Economics and Policy, Production Economics, Resource /Energy Economics and Policy,

Patching task-level robot controllers based on a local µ-calculus formula

We present a method for mending strategies for GR(1) specifications. Given the addition or removal of edges from the game graph describing a problem (essentially transition rules in a GR(1) specification), we apply a µ-calculus formula to a neighborhood of states to obtain a “local strategy” that navigates around the invalidated parts of an original synthesized strategy. Our method may thus avoid global resynthesis while recovering correctness with respect to the new specification. We illustrate the results both in simulation and on physical hardware for a planar robot surveillance task

Computing in unipotent and reductive algebraic groups

The unipotent groups are an important class of algebraic groups. We show that techniques used to compute with finitely generated nilpotent groups carry over to unipotent groups. We concentrate particularly on the maximal unipotent subgroup of a split reductive group and show how this improves computation in the reductive group itself.Comment: 22 page