Uncertainty of net present value calculations and the impact on applying integrated maintenance approaches to the UK rail industry

The Public performance indicator (PPI) is an important Key Performance Indicator for Network Rail and monitored carefully by the organisation and their external stakeholders. Condition monitoring is of increasing interest within network rail as a suitable method for increasing asset reliability and improving the PPI metric. As condition monitoring methods are identified each will need assessment to establish the cost and benefit. Benefit can be measured in cost savings as poor PPI performance results in fines. Within many industries Net Present Value (NPV) calculations are used to determine how quickly investments will break-even. Cost-risk is a term that is used to describe the financial impact of an unexpected event (a risk). This paper outlines a more detailed approach to calculating NPV which considers the cost-risk effect of changes of the denial of service charging rate. NPV prediction is of importance when assessing when to deploy different fault detection strategies to maintenance issues, and therefore the cost-risk of the NPV calculation should be used to support asset management decisions

Using experiments and expert judgment to model catchability of Pacific rockfishes in trawl surveys, with application to bocaccio (Sebastes paucispinis) off British Columbia

The time series of abundance indices for many groundfish populations, as determined from trawl surveys, are often imprecise and short, causing stock assessment estimates of abundance to be imprecise. To improve precision, prior probability distributions (priors) have been developed for parameters in stock assessment models by using meta-analysis, expert judgment on catchability, and empirically based modeling. This article presents a synthetic approach for formulating priors for rockfish trawl survey catchability (qgross). A multivariate prior for qgross for different surveys is formulated by using 1) a correction factor for bias in estimating fish density between trawlable and untrawlable areas, 2) expert judgment on trawl net catchability, 3) observations from trawl survey experiments, and 4) data on the fraction of population biomass in each of the areas surveyed. The method is illustrated by using bocaccio (Sebastes paucipinis) in British Columbia. Results indicate that expert judgment can be updated markedly by observing the catch-rate ratio from different trawl gears in the same areas. The marginal priors for qgross are consistent with empirical estimates obtained by fitting a stock assessment model to the survey data under a noninformative prior for qgross. Despite high prior uncertainty (prior coefficients of variation ≥0.8) and high prior correlation between qgross, the prior for qgross still enhances the precision of key stock assessment quantities

The Meaning of Privatization

Privatization is a fuzzy concept that evokes sharp political reactions. It covers a great range of ideas and policies, varying from the eminently reasonable to the wildly impractical. Yet however varied and at times unclear in its meaning, privatization has unambiguous political origins and objectives. It emerges from the countermovement against the growth of government in the West and represents the most serious conservative effort of our time to formulate a positive alternative. Privatization proposals do not aim merely to return services to their original location in the private sphere. Some proposals seek to create new kinds of market relations and promise results comparable or superior to conventional public programs. Hence it is a mistake to define and dismiss the movement as simply a replay of traditional opposition to state intervention and expenditure. The current wave of privatization initiatives opens a new chapter in the conflict over the public-private balance

Pain scales for assessing pain intensity in the elderly

This issue of eMedRef provides information to clinicians on using pain scales to assess pain in the elderly

Porphyria cutanea tarda

This issue of eMedRef provides information to clinicians on the pathophysiology, diagnosis, and therapeutics of porphyria cutanea tarda

Ares I-X Separation and Reentry Trajectory Analyses

The Ares I-X Flight Test Vehicle was launched on October 28, 2009 and was the first and only test flight of NASA s two-stage Ares I launch vehicle design. The launch was successful and the flight test met all of its primary and secondary objectives. This paper discusses the stage separation and reentry trajectory analysis that was performed in support of the Ares I-X test flight. Pre-flight analyses were conducted to assess the risk of stage recontact during separation, to evaluate the first stage flight dynamics during reentry, and to define the range safety impact ellipses of both stages. The results of these pre-flight analyses were compared with available flight data. On-board video taken during flight showed that the flight test vehicle successfully separated without any recontact. Reconstructed trajectory data also showed that first stage flight dynamics were well characterized by pre-flight Monte Carlo results. In addition, comparisons with flight data indicated that the complex interference aerodynamic models employed in the reentry simulation were effective in capturing the flight dynamics during separation. Finally, the splash-down locations of both stages were well within predicted impact ellipses

Dysmenorrhea: diagnostics

This issue of eMedRef provides information to clinicians on the pathophysiology, diagnosis, and therapeutics of dysmenorrhea

Reviews

Francis Botto, Dictionary of Multimedia and Internet Applications ‐ A Guide for Developers and Users, Chichester, UK: John Wiley & Sons, 1999. ISBN: 0–471–986240. Hardback, x+362 pages, £34.95