Heuristics for railway infrastructure saturation

AbstractThis research concerns the problem of the evaluation of the railway infrastructure capacity. It is an important question when railway authorities have to choose between different infrastructure investment projects. We developped independently two heuristic approaches to solve the infrastructure saturation problem. The first is based on a constraint programming model which is solved using a greedy heuristic. The second approach identifies the saturation problem as a unicost set packing problem and its resolution is ensured by an adaption of GRASP metaheuristic. Currently, both resolution techniques are not in competition. The goal is to grasp the resolution ability of the heuristics and to analyse the kind of solutions produced. The Pierrefitte-Gonesse junction has been used as experimental support. A software environment allows to simulate several timetables involving TGV, Inter City and Freight trains

CANU-ReID: A Conditional Adversarial Network for Unsupervised person Re-IDentification

Unsupervised person re-ID is the task of identifying people on a target data set for which the ID labels are unavailable during training. In this paper, we propose to unify two trends in unsupervised person re-ID: clustering & fine-tuning and adversarial learning. On one side, clustering groups training images into pseudo-ID labels, and uses them to fine-tune the feature extractor. On the other side, adversarial learning is used, inspired by domain adaptation, to match distributions from different domains. Since target data is distributed across different camera viewpoints, we propose to model each camera as an independent domain, and aim to learn domain-independent features. Straightforward adversarial learning yields negative transfer, we thus introduce a conditioning vector to mitigate this undesirable effect. In our framework, the centroid of the cluster to which the visual sample belongs is used as conditioning vector of our conditional adversarial network, where the vector is permutation invariant (clusters ordering does not matter) and its size is independent of the number of clusters. To our knowledge, we are the first to propose the use of conditional adversarial networks for unsupervised person re-ID. We evaluate the proposed architecture on top of two state-of-the-art clustering-based unsupervised person re-identification (re-ID) methods on four different experimental settings with three different data sets and set the new state-of-the-art performance on all four of them. Our code and model will be made publicly available at https://team.inria.fr/perception/canu-reid/

A Survey on Cost and Profit Oriented Assembly Line Balancing

http://www.nt.ntnu.no/users/skoge/prost/proceedings/ifac2014/media/files/0866.pdfInternational audienceProblems, approaches and analytical models on assembly line balancing that deal explicitly with cost and profit oriented objectives are analysed. This survey paper serves to identify and work on open problems that have wide practical applications. The conclusions derived might give insights in developing decision support systems (DSS) in planning profitable or cost efficient assembly lines

Minimizing setup cost for multipart production lines

http://www.usc.edu/dept/ise/caie/Checked%20Papers%20%5Bruhi%2012th%20sept%5D/word%20format%20papers/REGISTRATION%20PAID%20PAPERS%20FOR%20PROCEEDINGS/pdf/170%2014%20MINIMIZING%20SETUP%20COST%20FOR%20MULTI-PART%20PRODUCTION%20LINES.pdfInternational audienceAn industrial engineering problem is under study. It consists in optimal configuration of a multi-part production line. A line is a sequence of workstations, at which the manufacturing operations at each workstation are executed in parallel. Parallel execution of operations is inherent for multi-spindle heads in mechanical industry, for example. Each machine part of a specific type f requires a specific set of operations. Different sets can contain common operations. The total number of operations per workstation cannot exceed a given upper bound. Parts move along the stations in the same direction. If there is at least one operation attributed to the part type arriving at a station, this station is set up. Setup costs are part type dependent and they appear due to additional resources required for processing of a part at stations. There are two criteria: minimization of the number of stations, and minimization of the total setup cost. A solution of the problem implies the number of stations and the assignment of operations to these stations. Properties of an optimal solution were established. Basing on these properties, optimal algorithms were developed for the cases f = 2, f = 3, and an arbitrary f. The algorithms employ combinatorial optimization and linear algebra techniques. They run in a constant time if f is a constant

Minimisation du coût de setup pour des lignes d'usinage multi-produits

International audienceLe probl eme etudi e correspond a la con guration optimale d'une ligne d'usinage destin ee a la production de f types de pi eces usin ees. Il s'agit d'une s equence de stations, sur lesquelles les op erations d'usinage sont ex ecut ees en parall ele. Chaque pi ece a usiner requiert l'ex ecution un ensemble d'op erations sp eci ques d ependant de son type. Le nombre total d'op erations par station ne peut pas exc eder une borne sup erieure donn ee. Les pi eces sont transport ees le long des stations dans la m^eme direction l'une apr es l'autre. S'il y a au moins une op eration a ect ee a une station qui correspond au type de pi ece en production, alors cette station est mise en service. Les co^uts de pr eparation li es a ces mises en service d ependent du type de pi ece et ils apparaissent en raison de ressources suppl ementaires requises pour le traitement d'une pi ece sur des stations. Il y a deux crit eres : la minimisation du nombre de stations et la minimisation du co^ut total de mises en courses. Une solution du probl eme implique le nombre de stations et l'a ectation des op erations a ces stations. Les propri et es d'une solution optimale ont et e etablies. En s'appuyant sur ces propri et es, des algorithmes optimaux ont et e d evelopp es pour les cas f = 2, f = 3, et un f arbitraire

An ant colony optimization inspired algorithm for the set packing problem with application to railway infrastructure

http://www.emse.fr/~delorme/Papiers/MIC05/MIC05_resume.pdfInternational audienceThe paper concerns an Ant Colony Optimisation (ACO) procedure as approximation method for the railway infrastructure capacity (RIC) problem. Railway infrastructure managers now have to deal with operators' requests for increased capacity. Planning the construction or reconstruction of infrastructures must be done very carefully due to the huge required invest- ments and the long term implications. Usually, assessing the capacity of one component of a rail system is done by measuring the maximum number of trains that can be operated on this component within a certain time period. In our work, we deal with two real situations. The first is Pierrefitte-Gonnesse crossing point located at the north of Paris. The second is the Lille-Flandres station which is the largest station in North of France. Measuring the capacity of junctions is a matter of solving an optimisation problem called the saturation problem [1], and which can be formulated as a Set Packing Problem (SPP). Given a finite set I = {1, . . . , n} of items and {Tj}, j 2 J = {1, . . . ,m}, a collection of m subsets of I, a packing is a subset P I such that |Tj \ P| 1, 8j 2 J. The set J can be also seen as a set of exclusive con- straints between some items of I. Each item i 2 I has a positive weight denoted by ci and the aim of the SPP is to calculate the packing which maximises the total weight. This proble

L’impact du suicide sur l’aidant

Le suicide (« meurtre de soi-même ») pose à tous une question essentielle: qu'est-ce que l'expression manifeste du désir de mort mobilise en soi et chez les autres? Cette interrogation s'avère particulièrement difficile à soulever pour l'aidant ou le soignant confronté à la mort volontaire d'un client ou d'un patient. À travers l'histoire d'un suicide en institution, les auteurs évoquent la nature des mécanismes défensifs mis enjeu par l'équipe soignante. Sidération traumatique, dénégation, déni, culpabilité, mouvements dépressifs sont autant de réactions individuelles et collectives qui s'opposent au travail du deuil, et menacent la cohésion institutionnelle. Les membres de l'« institution en crise » ont à réguler leurs tensions, en évitant de répondre par le retrait, la banalisation, la hantise du suicide, ou l'instauration de pseudo-solutions « pragmatiques ». Il s'agit d'éviter en particulier l'annulation ou le déplacement d'une nécessaire reflexion de tous sur la genèse, les implications et les conséquences du suicide intra-institutionnel. Les auteurs rappellent les principaux fondements et les modalités d'une exploration en équipe de ces phénomènes qui - en l'absence de « travail de la crise » - risquent de situer l'institution dans l'impasse d'un questionnement consistant seulement à savoir à quel moment, faute de s'être retournée, elle se serait détournée de son patient en souffrance.Suicide ("the killing of one's self) raises one crucial question: what does the manifest desire of death bring out in oneself and in others? For those providing care and support who are confronted with the voluntary death of a client or patient, the question is particularly difficult to address. Using the story of a suicide in an institution, the authors reveal the nature of defense mechanisms at play within the group of caregivers. Whether it be a traumatic daze, denial, guilt or depression, these individual and collective reactions to the event hinder the mourning process and threaten cohesion within the institution. Members of an "institution in crisis" must try to relieve their tensions by refraining from withdrawal, banalities, being haunted by suicide and implementing pseudo-solutions. The purpose of such an exercise is especially to avoid the cancellation or displacement of necessary thougt process about the origins, implications and consequences of a suicide taking place within an institution. The authors discuss the founding principles and guidelines for group exploration of these phenomena. Without this coming-to-terms with the crisis, the authors point out that the institution could find itself in a rut where discussion focuses only on when and where things went wrong, and how it turned its back on a suffering patient

Workforce minimization for a mixed-model assembly line in the automotive industry

A paced assembly line consisting of several workstations is considered. This line is intended to assemble products of different types. The sequence of products is given. The sequence of technological tasks is common for all types of products. The assignment of tasks to the stations and task sequence on each station are known and cannot be modified, and they do not depend on the product type. Tasks assigned to the same station are performed sequentially. The processing time of a task depends on the number of workers performing this task. Workers are identical and versatile. If a worker is assigned to a task, he/she works on this task from its start till completion. Workers can switch between the stations at the end of each task and the time needed by any worker to move from one station to another one can be neglected. At the line design stage, it is necessary to know how many workers are necessary for the line. To know the response to this question we will consider each possible takt and assign workers to tasks so that the total number of workers is minimized, provided that a given takt time is satisfied. The maximum of minimal numbers of workers for all takts will be considered as the necessary number of workers for the line. Thus, the problem is to assign workers to tasks for a takt. We prove that this problem is NP-hard in the strong sense, we develop an integer linear programming formulation to solve it, and propose conventional and randomized heuristics

First results from the Canada-France High-z Quasar Survey: Constraints on the z=6 quasar luminosity function and the quasar contribution to reionization

We present preliminary results of a new quasar survey being undertaken with multi-colour optical imaging from the Canada-France-Hawaii Telescope. The current data consists of 3.83 sq. deg. of imaging in the i' and z' filters to a 10 sigma limit of z'<23.35. Near-infrared photometry of 24 candidate 5.7<z<6.4 quasars confirms them all to be low mass stars including two T dwarfs and four or five L dwarfs. Photometric estimates of the spectral type of the two T dwarfs are T3 and T6. We use the lack of high-redshift quasars in this survey volume to constrain the z=6 quasar luminosity function. For reasonable values of the break absolute magnitude M*_1450 and faint-end slope alpha, we determine that the bright-end slope beta>-3.2 at 95% confidence. We find that the comoving space-density of quasars brighter than M_1450=-23.5 declines by a factor >25 from z=2 to z=6, mirroring the decline observed for high-luminosity quasars. We consider the contribution of the quasar population to the ionizing photon density at z=6 and the implications for reionization. We show that the current constraints on the quasar population give an ionizing photon density <<30% that of the star-forming galaxy population. We conclude that active galactic nuclei make a negligible contribution to the reionization of hydrogen at z~6.Comment: 9 pages, 6 figures, ApJ, in pres

Optimizing Modular Machining Line Design Problem with Mixed Activation Mode of Machining Units

A modular transfer line designing problem is investigated. The problem is to find the best subset of modules (machining units) from a given set and to assign them to different stations so that technological constraints and cycle upper limit are respected and the line cost is minimal. The investigated lines have a mixed activation mode for the machining units of each station, i.e. the units of each station are arranged into a series of stages such that each stage is composed of several units activated in parallel. A mixed integer program approach is proposed to model and solve the corresponding design problem. Improvements are suggested in order to reduce the model size and speed up the computations