A holistic approach to railway infrastructure asset management

In the railway industry asset management decisions are focused on the maintenance, enhancement and renewal of assets in order to ensure a required level of dependability and improvement in services at the lowest whole life costs. To achieve these objectives system lifecycle models, rather than individual asset models,= offer a greater advantage. The paper presents a modelling approach developed for constructing multi asset system models to support well-informed railway infrastructure asset management decisions. The models are built using the Petri Net formalism and are analysed by a means of Monte Carlo simulations. A specific example of the railway superstructure model is presented. Its simulation results demonstrate the superiority of the system-wide model against individual asset models in terms of its accuracy in predicting the superstructure (system) performance and information available to support asset management decisions. Furthermore, by using the multi-asset system model interdependencies among maintenance regimes of different assets and different parts of the infrastructure can be modelled

System-wide assessment of intervention strategies for railway infrastructure

The existing railway infrastructure exhibits faster degradation rates and requires more maintenance effort as a result of increased utilisation. At the same time, due to increased numbers of freight and commuter trains obtaining access to the railway infrastructure to carry out maintenance and repairs, not to mention major enhancements, is becoming more problematic. Furthermore, safety measures put in place in the event of infrastructure faults or delayed completion of intervention activities will cause greater disruptions to train services in the parts of the network with intense train traffic. Taking a system wide view is, therefore, vital for developing efficient intervention strategies that could deliver the desired infrastructure outputs. In this paper we propose a modelling approach for simulation and analysis of railway track asset management strategies integrating different elements of the whole railway system. The approach uses a Petri net modelling technique to construct the railway system model. The model is built in a hierarchical, modular fashion, meaning that the system can be represented at any level of granularity and complexity, ranging from a single-asset system in a small segment of the network to a complex multi-asset system in a large geographical region. The impact of different asset management strategies on the infrastructure functionality and the operation of train services is assessed using the Monte Carlo simulation technique

Computation of oyster yields in Virginia

Also part of series: Special report from the Virginia Fisheries Laboratory ; no. 7

Status of MSX in Chesapeake Bay

Oystermen in lower Chesapeake Bay survived the ravages of Dermocystidium during some hot summers in the past decade only to be scourged by a new disease which appeared in 1969. We had learned to live with Dermocystidium by avoiding infected seed and limiting the number of hot summers oysters were held in infested areas. Now we have the more difficult problem of adjusting to MSX which is a devastating killer of oysters

Status of diseases of oysters in Chesapeake Bay

Oysters in lower Chesapeake Bay survived the ravages of Dermocystidium during some hot summers in the past decade only to be scourged by a new disease (MSX) which appeared in 1959. We had learned to live with Dermocystidium by avoiding infected seed and limiting the number of hot summers oysters were held in infested areas. Now we are faced with the more difficult problem of adjusting to MSX, which is a devastating killer of oysters. The beginning of a new season of planting seed is an appropriate time to review our knowledge of teh various diseases of oysters

The Dogrib Birchbark Canoe Project

The Dogrib are one of the Athapaskan, or Dene groups occupying the Mackenzie Valley area in the Northwest Territories (see map). Their hunting canoes, though engineered for traversing a rugged landscape, had elegant and flowing lines. ... Although there is a reasonably good collection of archival photographs of Dogrib canoes, mostly due to the efforts of the anthropologist J. Alden Mason ..., the historical record has preserved little knowledge pertinent to canoe construction and use, and only a small number of canoes have survived in museum collections. During our recent archaeological research on two important Dogrib canoe routes, however, we recorded the remains of nearly 30 hunting canoes .... Today, in the Dogrib communities of Snare Lake, Rae Lakes, Wha Ti and Rae-Edzo, the oral tradition is full of canoeing and canoe-related stories and remembrances, although very few surviving elders actually built one in their youth. This fact, and the large number of canoes recorded in our research, gave us a new appreciation of the importance and role they had played in travel, and led to an exciting cultural revival project: to build and document a Dogrib birchbark canoe. ... [This article briefly describes the canoe project, sharing some of what the elders taught us about Dogrib hunting canoes.

Occurrence of MSX in live oysters in Rappahannock River

Sampling data

University of Colorado: 1972 Field Season on East Baffin Island

SEA ICE. Studies of surface energy budgets on the fast ice at Broughton Island 67°35' N, 63°50' W) were undertaken from late May to August 1972. The program included micrometeorological measurements on the fast ice and ice thickness surveys. Climatological observations including radiation studies begun in June 1971 by The Institute of Arctic and Alpine Research at a site in Broughton village were continued. The summer of 1972 was one of unusually severe ice conditions for this section of Davis Strait, and the results of our winter 1971-72 and summer 1972 fieldwork are being examined together with synoptic data in an attempt to understand this situation. Meteorological satellite data are being analyzed to obtain regional extrapolations of synoptic surface energy budgets. BOAS GLACIER. The Boas Glacier was visited in early June, at which time snow pits and probing were used to estimate the winter balance. The mean snow depth based on 190 probes was 0.948 m with a standard error of ±0.06 m. Average snow density was 0.326 g/cm³ giving a specific winter balance of 0.31 m H2O. The glacier could not be visited in August due to extremely bad ice conditions, but on the basis of the weather in previous years we predict that the net specific balance will be positive and greater than 0.3 m H2O. The strain diamond was remeasured and analysis indicates that the principal strain axis is directed down-glacier and shows a compressive strain of 10**-6 yr (based on 2 years of measurements). Using the Boas Glacier mass balance data, a discriminant equation has been developed based on September to May accumulation at Broughton Island, and accumulated summer degree days (June, July, August). Investigations of other mass balance data suggest that the Broughton Island data constitute a sensitive predictor of mass balances as far north as Devon Island. This finding ... indicates a broad similarity of climatic events throughout major sections of the Arctic. QUATERNARY GEOLOGY. Investigations on Neoglacial, Wisconsin and pre-Wisconsin local ice advances were carried out in the area between Cape Dyer and Padloping Island. Echo soundings indicated the presence of glacio-marine deltas at depths of 30 m below sea level. Dr. G. Boulton, University of East Anglia, Norwich, visited the area and collected a peat monolith in front of the Maktak Glacier, and Dr. M. Church, University of British Columbia, carried out investigations on the Maktak sandur

Pavement maintenance scheduling using genetic algorithms

This paper presents a new pavement management system (PMS) to achieve the optimal pavement maintenance and rehabilitation (M&R) strategy for a highway network using genetic algorithms (GAs). Optimal M&R strategy is a set of pavement activities that both minimise the maintenance cost of a highway network and maximise the pavement condition of the road sections on the network during a certain planning period. NSGA-II, a multi-objective GA, is employed to perform pavement maintenance optimisation because of its robust search capabilities and constraint handling method that deal with the multi-objective and multi-constrained optimisation problems. In the proposed approach, both deterministic and probabilistic pavement age gain models are utilised for evaluating the evolution of pavement condition over time because of their simplicity of application. The proposed PMS is applied to a case study network that consists of different kinds of road sections. The results obtained indicate that the model is a valuable toolbox for pavement engineers