Automobile ride quality experiments correlated to iso-weighted criteria

As part of an overall study to evaluate the usefulness of ride quality criteria for the design of improved ground transportation systems an experiment was conducted involving subjective and objective measurement of ride vibrations found in an automobile riding over roadways of various roughness. Correlation of the results led to some very significant relationships between passenger rating and ride accelerations. The latter were collapsed using a frequency-weighted root mean square measure of the random vibration. The results suggest the form of a design criterion giving the relationship between ride vibration and acceptable automobile ride quality. Further the ride criterion is expressed in terms that relate to rides with which most people are familiar. The design of the experiment, the ride vibration data acquisition, the concept of frequency weighting and the correlations found between subjective and objective measurements are presented

Linking teaching and research in disciplines and departments

This paper supports the effective links between teaching and discipline-based research in disciplinary communities and in academic departments. It is authored by Alan Jenkins, Mick Healey and Roger Zetter

Roadless space and logging in intact forest landscapes of the Congo Basin

Background: Forest degradation in tropical regions is often associated with roads built for selective logging. Forest areas that are not accessible by roads are considered valuable because they provide habitat that is not immediately impacted by major human activities. The protection of such Intact Forest Landscapes (IFL) is high on the biodiversity conservation agenda, leading to a motion of the Forest Stewardship Council (FSC) to better protect IFL in certified forest concessions. However, in many parts of Central Africa logging takes place at very low intensities and most roads are abandoned after few years of timber harvesting. Taking limited road persistence into account we asked: How did road networks in FSC certified concessions affect IFL? Methods: Intact forest landscapes can be conserved by retention of “roadless space”, a concept based on distance to the nearest road from any point. We used the Empty-Space Function, a general statistical tool from stochastic geometry, to calculate roadless space based on time series of LANDSAT images. We followed the spatial and temporal dynamics of logging roads in a part of the Congo Basin that has recently seen rapid expansion of road networks for selective logging. We compared the development of roadless space in certified and non-certified logging concessions inside and outside areas declared as being IFL in the year 2000. Results: The persistence of logging roads was limited over time, with only 12% of the overall network being permanently open. However, also taking only actively used roads into account, roadless space inside IFL has decreased rapidly due to expansion of logging into previously unlogged areas. Concessions that are now certified by FSC showed a slower rate of decrease before certification but after that their roadless space decreased to a level comparable to non-FSC concessions. The established concessions outside IFL showed a slight increase in roadless space due to forest recovery on abandoned roads. Conclusions: We recommend that forest management should make the preservation of large connected forest areas a top priority by effectively monitoring - and limiting – the occupation of space by roads that are accessible at the same time. Given the strong dynamics in road detectability, we challenge the static definition of intact forest landscapes based on a buffer around any road ever detected. Instead we suggest the empty space function as a viable alternative to calculate roadless space. (Texte intégral

The development of a measure of social care outcome for older people. Funded/commissioned by: Department of Health

An essential element of identifying Best Value and monitoring cost-effective care is to be able to identify the outcomes of care. In the field of health services, use of utility-based health related quality of life measures has become widespread, indeed even required. If, in the new era of partnerships, social care outcomes are to be valued and included we need to develop measures that reflect utility or welfare gain from social care interventions. This paper reports on a study, commissioned as part of the Department of Health’s Outcomes of Social Care for Adults Initiative, that developed an instrument and associated utility indexes that provide a tool for evaluating social care interventions in both a research and service setting. Discrete choice conjoint analysis used to derive utility weights provided us with new insights into the relative importance of the core domains of social care to older people. Whilst discrete choice conjoint analysis is being increasingly used in health economics, this is the first study that has attempted to use it to derive a measure of outcome

A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)

A detailed analysis of the evolution of the properties of core-jet systems within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a power-law relationship between jet intensity and width that suggests for the typical jet, little if any energy is lost as it moves away from its core. Using VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be aligned with the the direction of emission on kiloparsec scales. We also found that this alignment improves as the jets move farther from their cores on projected scales as small as ~50-100 pc. This suggests that realignment of jets on these projected scales is relatively common. We typically find a modest amount of bending (a change in jet position angle of ~5 deg.) on these scales, suggesting that this realignment may typically occur relatively gradually.Comment: Accepted to ApJ, 20 pages, 8 figure

A Categorical Equivalence between Generalized Holonomy Maps on a Connected Manifold and Principal Connections on Bundles over that Manifold

A classic result in the foundations of Yang-Mills theory, due to J. W. Barrett ["Holonomy and Path Structures in General Relativity and Yang-Mills Theory." Int. J. Th. Phys. 30(9), (1991)], establishes that given a "generalized" holonomy map from the space of piece-wise smooth, closed curves based at some point of a manifold to a Lie group, there exists a principal bundle with that group as structure group and a principal connection on that bundle such that the holonomy map corresponds to the holonomies of that connection. Barrett also provided one sense in which this "recovery theorem" yields a unique bundle, up to isomorphism. Here we show that something stronger is true: with an appropriate definition of isomorphism between generalized holonomy maps, there is an equivalence of categories between the category whose objects are generalized holonomy maps on a smooth, connected manifold and whose arrows are holonomy isomorphisms, and the category whose objects are principal connections on principal bundles over a smooth, connected manifold. This result clarifies, and somewhat improves upon, the sense of "unique recovery" in Barrett's theorems; it also makes precise a sense in which there is no loss of structure involved in moving from a principal bundle formulation of Yang-Mills theory to a holonomy, or "loop", formulation.Comment: 20 page

A new tool to calculate roadless space in forest landscapes, applied in the Congo basin

New global strategies for road building require innovative tools to analyze linear patterns and their spatial distribution and to evaluate their environmental impacts. Roads not only present physical barriers to wildlife but also provide access for human and biological invasions. In tropical regions especially, forest degradation has been associated with roads built for selective logging into formerly intact forest landscapes. To quantify to what extent ecosystems are influenced by roads, it is important not only to know road length density but also their location in a landscape unit. The concept of roadless space is based on distance to the nearest road from any point. We present the computation of this distribution using the Empty-Space-Function, a general statistical mathematical tool based on stochastic geometry and random sets theory. We demonstrate the applicability of this well-defined probability function to calculate roadless space based on vector road data. In a Congo Basin case study we compared the temporal development of road networks inside different logging concessions over time. We hypothesized that roadless space decreases, even when the rate of wood volume harvest remains constant. Based on LANDSAT time series covering the last 29 years, we assessed accessible roads in relation with the river network and calculated the roadless space at different points in time. As expected, roadless space decreased continuously throughout most concessions, despite a drop in total annual harvest volume after 2008 and independent of forest certification schemes. We recommend that measures to reduce impacts of selective logging should not only be based on the extraction of timber, but should also include the total area impacted by roads. The Empty-Space-Function provides a rigorous mathematical description and a straightforward way to assess intact forest landscapes and is therefore highly applicable to road impact evaluation in conservation science

Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey (VIPS). This large, flux-limited sample of active galactic nuclei (AGN) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lacs tend to be similar to the non-LAT BL Lacs, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQs can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lacs. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGN.Comment: 32 pages, 9 figures, accepted by Ap