scholarly journals A New Approach to Shortest Route Finding in a Railway Network with Two Track Gauges and Gauge Changeovers

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Alberto Almech ◽  
Eugenio Roanes-Lozano ◽  
Carmen Solano-Macías ◽  
Antonio Hernando
Keyword(s):  
Computer Algebra ◽  
Computer Algebra System ◽  
Ad Hoc ◽  
Research Projects ◽  
Railway Network ◽  
New Approach ◽  
Shortest Route ◽  
Route Finding ◽  
Route Algorithm

The Spanish railway network is a complex one, due to the existence of standard gauge (1,435 mm), Iberian gauge (1,668 mm), and dual gauge (with three rails) subnetworks, as well as connections between the two first subnetworks (at the so-called gauge changeovers), usable by dual gauge trains. Two of the authors developed a package for shortest route finding, and consumes, costs, and emissions calculations in the Spanish railway network (within the frame of two research projects funded by the Fundación de los Ferrocarriles Españoles–Spanish Railways Foundation). Nevertheless, the approach required from a curious specific algorithm to be developed ad hoc. In this paper, a much simpler approach to shortest route finding in such a network, which merges the three subnetworks into two and considers the gauge changeovers as connections between the two new subnetworks, is detailed. This approach allows to use any standard shortest route algorithm. It has been implemented in the computer algebra system Maple and is applied in this paper both to small specific cases and to the whole Spanish railway network.

Generation of Correlated Logistic-Normal Random Variates for Medical Decision Trees

1998 ◽  
Vol 37 (03) ◽  
pp. 235-238 ◽  
Author(s):  
M. El-Taha ◽  
D. E. Clark
Keyword(s):  
Monte Carlo ◽  
Decision Trees ◽  
Computer Algebra ◽  
Taylor Series ◽  
Computer Algebra System ◽  
Random Variable ◽  
Monte Carlo Analysis ◽  
Normal Random Variable ◽  
Medical Decision ◽  
Theoretical Results

AbstractA Logistic-Normal random variable (Y) is obtained from a Normal random variable (X) by the relation Y = (ex)/(1 + ex). In Monte-Carlo analysis of decision trees, Logistic-Normal random variates may be used to model the branching probabilities. In some cases, the probabilities to be modeled may not be independent, and a method for generating correlated Logistic-Normal random variates would be useful. A technique for generating correlated Normal random variates has been previously described. Using Taylor Series approximations and the algebraic definitions of variance and covariance, we describe methods for estimating the means, variances, and covariances of Normal random variates which, after translation using the above formula, will result in Logistic-Normal random variates having approximately the desired means, variances, and covariances. Multiple simulations of the method using the Mathematica computer algebra system show satisfactory agreement with the theoretical results.

A New Approach for the Reliability of Vehicular Ad hoc Networks

2018 ◽  
Author(s):  
Abdallah Dabboussi ◽  
Jaafar Gaber ◽  
Maxime Wack ◽  
Raed Kouta ◽  
Bachar EL Hassan ◽  
...  
Keyword(s):  
Ad Hoc Networks ◽  
Vehicular Ad Hoc Networks ◽  
Ad Hoc ◽  
New Approach ◽  
Hoc Networks

scholarly journals SAT modulo discrete event simulation applied to railway design capacity analysis

2021 ◽  
Author(s):  
Bjørnar Luteberget ◽  
Koen Claessen ◽  
Christian Johansen ◽  
Martin Steffen
Keyword(s):  
Discrete Event Simulation ◽  
Construction Projects ◽  
Software Verification ◽  
Ad Hoc ◽  
Discrete Event ◽  
Capacity Analysis ◽  
Railway Network ◽  
Event Simulation ◽  
Design Engineers ◽  
Railway Capacity

AbstractThis paper proposes a new method of combining SAT with discrete event simulation. This new integration proved useful for designing a solver for capacity analysis in early phase railway construction design. Railway capacity is complex to define and analyze, and existing tools and methods used in practice require comprehensive models of the railway network and its timetables. Design engineers working within the limited scope of construction projects report that only ad-hoc, experience-based methods of capacity analysis are available to them. Designs often have subtle capacity pitfalls which are discovered too late, only when network-wide timetables are made—there is a mismatch between the scope of construction projects and the scope of capacity analysis, as currently practiced. We suggest a language for capacity specifications suited for construction projects, expressing properties such as running time, train frequency, overtaking and crossing. Such specifications can be used as contracts in the interface between construction projects and network-wide capacity analysis. We show how these properties can be verified fully automatically by building a special-purpose solver which splits the problem into two: an abstracted SAT-based dispatch planning, and a continuous-domain dynamics with timing constraints evaluated using discrete event simulation. The two components communicate in a CEGAR loop (counterexample-guided abstraction refinement). This architecture is beneficial because it clearly distinguishes the combinatorial choices on the one hand from continuous calculations on the other, so that the simulation can be extended by relevant details as needed. We describe how loops in the infrastructure can be handled to eliminate repeating dispatch plans, and use case studies based on data from existing infrastructure and ongoing construction projects to show that our method is fast enough at relevant scales to provide agile verification in a design setting. Similar SAT modulo discrete event simulation combinations could also be useful elsewhere where one or both of these methods are already applicable such as in bioinformatics or hardware/software verification.

scholarly journals Continuous Automotive Software Updates through Container Image Layers

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 739
Author(s):  
Nicholas Ayres ◽  
Lipika Deka ◽  
Daniel Paluszczyszyn
Keyword(s):  
Embedded System ◽  
Ad Hoc ◽  
New Technologies ◽  
Electronic Control Unit ◽  
Control Unit ◽  
New Approach ◽  
Automotive Software ◽  
Software Updating ◽  
Software Updates ◽  
Functional Software

The vehicle-embedded system also known as the electronic control unit (ECU) has transformed the humble motorcar, making it more efficient, environmentally friendly, and safer, but has led to a system which is highly dependent on software. As new technologies and features are included with each new vehicle model, the increased reliance on software will no doubt continue. It is an undeniable fact that all software contains bugs, errors, and potential vulnerabilities, which when discovered must be addressed in a timely manner, primarily through patching and updates, to preserve vehicle and occupant safety and integrity. However, current automotive software updating practices are ad hoc at best and often follow the same inefficient fix mechanisms associated with a physical component failure of return or recall. Increasing vehicle connectivity heralds the potential for over the air (OtA) software updates, but rigid ECU hardware design does not often facilitate or enable OtA updating. To address the associated issues regarding automotive ECU-based software updates, a new approach in how automotive software is deployed to the ECU is required. This paper presents how lightweight virtualisation technologies known as containers can promote efficient automotive ECU software updates. ECU functional software can be deployed to a container built from an associated image. Container images promote efficiency in download size and times through layer sharing, similar to ECU difference or delta flashing. Through containers, connectivity and OtA future software updates can be completed without inconveniences to the consumer or incurring expense to the manufacturer.

The Maple computer algebra system: A review

1995 ◽  
Vol 10 (3) ◽  
pp. 329-337 ◽  
Author(s):  
John Hutton ◽  
James Hutton
Keyword(s):  
Computer Algebra ◽  
Computer Algebra System ◽  
System A
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