MocNet Simulation Specification

This document outlines the simulation to be developed in the MocNet project. It will be a discrete event simulation using next-event incrementing to advance time. As we're interested in cell-level data, we will simulate the movement between cells according to a probabilistic random walk. Despite this coarse discretisation of space, some underlying geographical features will be captured by the probability matrices. We note that even simulations that capture the geography more precisely will merge into our simulation when only returning cell-level data. The MocNet Simulation will also include some temporal dependencies caused by e.g. commuting. The simulation consists of two different parts: the mobility simulation and a call arrival simulation. Each part will be presented below. Also, two different geographical environments and three anomaly situations will be simulated: a road with an accident and a town centre with a flash mob and a flee situation

Evaluation of planning policies for marshalling track allocation using simulation

Planning the operational procedures in a railway marshalling yard is a complex problem. When a train arrives at a marshalling yard, it is uncoupled on an arrival yard and then its cars are rolled to a classification yard. All cars should eventually be rolled to the classification track that has been assigned to the train they’re supposed to depart with. However, there is normally not enough capacity to compound all trains at once. In Sweden, cars arriving before a track has been assigned to their train can be stored on separate tracks called mixing tracks. All cars on mixing tracks will be pulled back to the arrival yard, and then rolled to the classification yard again to allow for reclassification. Today all procedures are planned by experienced dispatchers, but there are no documented strategies or guidelines for efficient manual planning. The aim of this paper is to examine operational planning strategies that could help dispatchers find a feasible marshalling schedule that minimizes unnecessary mixing. In order to achieve this goal, two different online planning strategies have been tested using deterministic and stochastic simulation. The Hallsberg marshalling yard was used as a case study, and was simulated for the time period between December 2010 and May 2011. The first tested strategy simply assigns tracks to trains on a first come-first served basis, while the second strategy uses time limits to determine when tracks should be assigned to departing trains. The online planning algorithms have been compared with an offline optimized track allocation. The results from both the deterministic and the stochastic simulation show that the optimized allocation is better than all online strategies and that the second strategy with a time limit of 32 hours is the best online method

On the delivery robustness of train timetables with respect to production replanning possibilities

Measuring timetable robustness is a complex task. Previous efforts have mainly been focused on simulation studies or measurements of time supplements. However, these measurements don't capture the production flexibility of a timetable, which is essential for measuring the robustness with regard to the trains' commercial activity commitments, and also for merging the goals of robustness and efficiency. In this article we differentiate between production timetables and delivery timetables. A production timetable contains all stops, meetings and switch crossings, while a delivery timetable only contains stops for commercial activities. If a production timetable is constructed such that it can easily be replanned to cope with delays without breaking any commercial activity commitments it provides delivery robustness without compromising travel efficiency. Changing meeting locations is one of the replanning tools available during operation, and this paper presents a new framework for heuristically optimising a given production timetable with regard to the number of alternative meeting locations. Mixed integer programming is used to find two delivery feasible production solutions, one early and one late. The area between the two solutions represents alternative meeting locations and therefore also the replanning enabled robustness. A case study from Sweden demonstrates how the method can be used to develop better production timetables

Opportunities and challenges with new railway planning approach in Sweden

Long lead times in railway planning can give rise to a significant discrepancy between the original plan and the traffic eventually operated, resulting in inefficient utilization of capacity. Research shows that the railway sector in Sweden would benefit from a different planning approach in which capacity consuming decisions are pushed forward in time whenever possible. This approach is currently being implemented at Trafikverket, the Swedish Transport Administration. With it follows a number of mathematical opportunities and challenges, some of which will be presented in this paper

Optimisation of simultaneous train formation and car sorting at marshalling yards

Efficient and correct freight train marshalling is vital for high quality carload freight transportations. During marshalling, it is desirable that cars are sorted according to their individual drop-off locations in the outbound freight trains. Furthermore, practical limitations such as non-uniform and limited track lengths and the arrival and departure times of trains need to be considered. This paper presents a novel optimisation method for freight marshalling scheduling under these circumstances. The method is based on an integer programming formulation that is solved using column generation and branch and price. The approach minimises the number of extra shunting operations that have to be performed, and is evaluated on real-world data from the Hallsberg marshalling yard in Sweden

Optimerad rangering: slutsatser och resultat från projektet RANPLAN

Sammanfattning Rapporten innehåller kortfattade slutsatser och resultat från en studie genomförd i projektet RANPLAN, som har utförts av SICS Swedish ICT AB på uppdrag av Trafikverket under åren 2010-2013. Fokus är på Hallsbergs rangerbangård, men resultaten är tillämpbara även på andra rangerbangårdar med vall. Datorkörningar visar att blanddragen kan öka kapaciteten på rangerbangårdar väsentligt, mätt i antalet samtidiga tåg som kan hanteras, till en kostnad av en ökad mängd vagnsrörelser. I en jämförande datorstudie av simulering och optimering framgick också att de optimala planerna var betydligt effektivare, mätt i antalet vagnsrörelser, än de simulerade planerna. Resultaten pekar tydligt på att datorstödd optimering av planeringsprocessen för rangerbangårdar både är praktiskt möjligt och kan ge stora effektivitetsvinster

Optimized shunting with mixed-usage tracks

We consider the planning of railway freight classification at hump yards, where the problem involves the formation of departing freight train blocks from arriving trains subject to scheduling and capacity constraints. The hump yard layout considered consists of arrival tracks of sufficient length at an arrival yard, a hump, classification tracks of non-uniform and possibly non-sufficient length at a classification yard, and departure tracks of sufficient length. To increase yard capacity, freight cars arriving early can be stored temporarily on specific mixed-usage tracks. The entire hump yard planning process is covered in this paper, and heuristics for arrival and departure track assignment, as well as hump scheduling, have been included to provide the neccessary input data. However, the central problem considered is the classification track allocation problem. This problem has previously been modeled using direct mixed integer programming models, but this approach did not yield lower bounds of sufficient quality to prove optimality. Later attempts focused on a column generation approach based on branch-and-price that could solve problem instances of industrial size. Building upon the column generation approach we introduce a direct arc-based integer programming model, where the arcs are precedence relations between blocks on the same classification track. Further, the most promising models are adapted for rolling-horizon planning. We evaluate the methods on historical data from the Hallsberg shunting yard in Sweden. The results show that the new arc-based model performs as well as the column generation approach. It returns an optimal schedule within the execution time limit for all instances but from one, and executes as fast as the column generation approach. Further, the short execution times of the column generation approach and the arc-indexed model make them suitable for rolling-horizon planning, while the direct mixed integer program proved to be too slow for this. Extended analysis of the results shows that mixing was only required if the maximum number of concurrent trains on the classification yard exceeds 29 (there are 32 available tracks), and that after this point the number of extra car roll-ins increases heavily

Teknisk slutrapport för RANPLAN - Beräkningstöd för planering och resursallokering på rangerbangården

I denna rapport presenteras de modeller och resultat som projektet/RANPLAN-beräkningsstöd för planering och resursallokering/ producerat. RANPLAN finansierades av Trafikverkets FUD-program (F 09-11546/AL50) och pågick från januari 2010 till december 2011. Under projektets gång har ett flertal heuristiska algoritmer och optimeringmodeller tagits fram som skulle kunna förbättra och förenkla planeringen vid rangerbangårdar. En demonstrator baserad på historiska data visar att metoderna är så pass skalbara och effektiva att de är attraktiva för kommersiell implementering. Vidare presenteras förslag på lämpliga effektivitets- och kvalitetsmått för rangering

Varför försvann neandertalmänniskorna? Moderna teorier, tester och tolkningar.

Since the type fossil was found, 153 years ago, the Neanderthal man has fascinated researchers and laymen alike. The Neanderthals lived in Eurasia for maybe 200,000 years but disappeared around the time when modern humans moved into Europe around 35,000 BP. New studes of bones and artifacts, and intriguing results of new DNA-technology, indicate that Homo neanderthalensis was a separate species- but probably the closes relative we will ever be able to know in detail- with a useful language, efficient lithic culture and various types of cognitive behaviours such as the use of pigments, funerals and complex technology. So why did they become extinct? The answer is multifactorial, and may include very rapid ("whiplash") climate deteriorations, followed by isolation of small groups of people in regions with a milder climate, e.g. on the Iberian peninsula, possibly resulting in inbreeding problems, which made them die out - unless they were exterminated by the modern invaders- before 25,000 BP

Interaction of enamel matrix proteins with human periodontal ligament cells

Dorothy Hodgkin Postgraduate Award for research studies (jointly funded by the Engineering and Physical Sciences Research Council, UK, and by Institut Straumann) and the Research Discretionary Funds of the Periodontology Unit, UCL Eastman Dental Institute. Financial support was also provided by the NIHR Comprehensive Biomedical Research Centre and by the WCU Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. R31-10069)