CNRS System Conception, Modelisation, and Optimsation Laboratory

Nancy, France

CNRS System Conception, Modelisation, and Optimsation Laboratory

Nancy, France
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Kacem I.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Rapine C.,University of Lorraine
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

In this paper we consider the open shop scheduling problem where the jobs have delivery times. The minimization criterion is the maximum lateness of the jobs. This problem is knwon to be NP-hard, even restricted to only 2 machines. We establish that any list scheduling algorithm has a performance ratio of 2. For a fixed number of machines, we design a polynomial time approximation scheme (PTAS) which represents the best possible result due to the strong NP-hardness of the problem.


Kacem I.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Kadri A.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Laroche P.,CNRS System Conception, Modelisation, and Optimsation Laboratory
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

This study addresses a 2-steps procedure applied to the inventory regulation problem in bicycle sharing-systems. The objective is to balance a network consisting of set of stations by using a single vehicle, with the aim of minimizing the waiting times during which the stations remain imbalanced. The balancing operations can be complex, especially when the network size is large. To solve the problem, we propose an approach based on different steps. First, the network is split into multiple zones according to fixed heights and widths. Secondly, the balancing problem is solved for each zone. Finally, the order in which the zones must be visited is defined. To solve these problems, we propose two heuristic algorithms based on the genetic algorithm and the nearest neighbour search method. The proposed procedure is simple and efficient, and presents some advantages with respect to the balancing considering a single area, in particular for large networks. Indeed, the numerical results show that the proposed regulation methodology has a lower computational cost and provides improved results compared to those when balancing a single area.


Habert O.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Gam M.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Kacem I.,CNRS System Conception, Modelisation, and Optimsation Laboratory
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

In this paper, we propose a solution to rank some chosen communication and information assistive technologies by using the well-known Multiple Criteria Decision-Making tool: fuzzy TOPSIS. There are many ways to restore or to assist disabled people in their daily communication and quest of information. Thanks to New Information and Communication Technologies (NICTs), communication assistive technology has started the path of a deep evolution. Indeed, numerous assistive devices using web technology and connected objects can be found. The main goal of this work is to propose assistive technology designer a tool to make prospective studies to guide them in their strategy and choice of new products' development. One of the advantages of MCDM method is to process with data coming from the disabled users, healthcare and social staff, researchers...


Monfort V.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Pfeuty M.,University of Bordeaux 1 | Klein M.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Colle S.,CNRS System Conception, Modelisation, and Optimsation Laboratory | And 4 more authors.
Neuropsychologia | Year: 2014

This case report on an epileptic patient suffering from a focal lesion at the junction of the right anterior insular cortex (AIC) and the adjacent inferior frontal cortex (IFC) provides the first evidence that damage to this brain region impairs temporal performance in a visual time reproduction task in which participants had to reproduce the presentation duration (3, 5 and 7. s) of emotionally-neutral and -negative pictures. Strikingly, as compared to a group of healthy subjects, the AIC/IFC case considerably overestimated reproduction times despite normal variability. The effect was obtained in all duration and emotion conditions. Such a distortion in time reproduction was not observed in four other epileptic patients without insular or inferior frontal damage. Importantly, the absolute extent of temporal over-reproduction increased in proportion to the magnitude of the target durations, which concurs with the scalar property of interval timing, and points to an impairment of time-specific rather than of non temporal (such as motor) mechanisms. Our data suggest that the disability in temporal reproduction of the AIC/IFC case would result from a distorted memory representation of the encoded duration, occurring during the process of storage and/or of recovery from memory and leading to a deviation of the temporal judgment during the reproduction task. These findings support the recent proposal that the anterior insular/inferior frontal cortices would be involved in time interval representation. © 2014 Elsevier Ltd.


Bousefsaf F.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Maaoui C.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Pruski A.,CNRS System Conception, Modelisation, and Optimsation Laboratory
Journal of Medical and Biological Engineering | Year: 2017

We propose, in this study, an original method that was developed to remotely measure the instantaneous pulse rate using photoplethysmographic signals that were recorded from a low-cost webcam. The method is based on a prior selection of pixels of interest using a custom segmentation that used the face lightness distribution to define different sub-regions. The most relevant sub-regions are automatically selected and combined by evaluating their respective signal to noise ratio. Performances of the proposed technique were evaluated using an approved contact sensor on a set of seven healthy subjects. Different experiments while reading, with motion or while performing common tasks on a computer were conducted in the laboratory. The proposed segmentation technique was compared with other benchmark methods that were already introduced in the scientific literature. The results exhibit high degrees of correlation and low pulse rate absolute errors, demonstrating that the segmentation we propose in this study outperform available region-of-interest selection methods. © 2017, Taiwanese Society of Biomedical Engineering.


Bousefsaf F.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Maaoui C.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Pruski A.,CNRS System Conception, Modelisation, and Optimsation Laboratory
Biomedical Signal Processing and Control | Year: 2013

Photoplethysmographic signals obtained from a webcam are analyzed through a continuous wavelet transform to assess the instantaneous heart rate. The measurements are performed on human faces. Robust image and signal processing are introduced to overcome drawbacks induced by light and motion artifacts. In addition, the respiration signal is recovered using the heart rate series by respiratory sinus arrhythmia, the natural variation in heart rate driven by the respiration. The presented algorithms are implemented on a mid-range computer and the overall method works in real-time. The performance of the proposed heart and breathing rates assessment method was evaluated using approved contact probes on a set of 12 healthy subjects. Results show high degrees of correlation between physiological measurements even in the presence of motion. This paper provides a motion-tolerant method that remotely measures the instantaneous heart and breathing rates. These parameters are particularly used in telemedicine and affective computing, where the heart rate variability analysis can provide an index of the autonomic nervous system. © 2013 Elsevier Ltd. All rights reserved.


Kadri A.A.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Kacem I.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Labadi K.,CNRS System Conception, Modelisation, and Optimsation Laboratory
Computers and Industrial Engineering | Year: 2016

Bicycle sharing systems are transportation systems that allow the users to rent a bicycle at one of many automatic rental stations scattered around the city, use them for a short travel and return them at any station. A crucial factor for the success of such a system is its ability to ensure a good quality of service to users. It means the availability of bicycles for pick-up and free places to return them. This is performed by means of a rebalancing operation, which consists in removing bicycles from some stations and transferring them to other stations, using dedicated vehicles. In this paper, we study the rebalancing vehicles routing problem by considering the static case. Vehicles conduct tours between stations to return them to their desired levels, which are known in advance, and each station must be visited exactly once and only once by a vehicle. This problem is similar to the traveling salesman problem with additional constraints. The aim is to find an optimal scheduling of the vehicle that minimizes the total waiting time of the stations in disequilibrium states. We propose several lower and upper bounds. These bounding procedures are used in a branch-and-bound algorithm. Computational experiments are carried out on a large set of instances and the obtained results show the effectiveness of our method. © 2016 Elsevier Ltd.


Kacem I.,CNRS System Conception, Modelisation, and Optimsation Laboratory
2013 2nd International Conference on Systems and Computer Science, ICSCS 2013 | Year: 2013

In this paper, we consider some practical scheduling problems under unavailability constraints (break-down periods, maintenance durations and/or setup times). Such problems can be met in different industrial environments and be associated to numerous real-life applications. The studied criteria are related to the maximum lateness minimization. The paper is organized in two main parts. The first part focuses on some special cases (makespan minimization when tails are equal and maximum lateness minimization when release dates are equal (see Section 2). The second part is devoted to the maximum lateness minimization (see Section 3). In each part, we present the main contributions and explain their principles (complexity results, heuristic algorithms and their worst-case performance, existing approximation schemes, exact methods, dynamic programming,...), Finally, Section 4 concludes the paper. © 2013 IEEE.


Habbas Z.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Amroun K.,University of Abderrahmane Mira de Béjaïa | Singer D.,CNRS System Conception, Modelisation, and Optimsation Laboratory
RAIRO - Operations Research | Year: 2016

Many real-world problems can be modelled as Constraint Satisfaction Problems (CSPs). Although CSP is NP-complete, it has been proved that non binary CSP instances may be efficiently solved if they are representable as Generalized Hypertree Decomposition (GHD) with small width. Algorithms for solving CSPs based on a GHD consider an extensional representation of constraints together with join and semi-join operations giving rise to new large constraint tables (or relations) needed to be temporarily saved. Extensional representation of constraints is quite natural and adapted to the specification of real problems but unfortunately limits significantly the practical performance of these algorithms. The present work tackles this problem using a compact representation of constraint tables. Consequently, to make algorithms compatible with this compact representation, new "compressed join" and "compressed semi-join" operations have to be defined. This last step constitutes our main contribution which, as far as we know, has never been presented. The correctness of this approach is proved and validated on multiple benchmarks. Experimental results show that using compressed relations and compressed operations improves significantly the practical performance of the basic algorithm proposed by Gottlob et al. for solving non binary CSPs with a Generalized Hypertree Decomposition. © 2016 EDP Sciences, ROADEF, SMAI.


Bousefsaf F.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Maaoui C.,CNRS System Conception, Modelisation, and Optimsation Laboratory | Pruski A.,CNRS System Conception, Modelisation, and Optimsation Laboratory
Proceedings of the 2013 7th International Conference on Pervasive Computing Technologies for Healthcare and Workshops, PervasiveHealth 2013 | Year: 2013

In the present paper, we introduce a new framework for detecting workload changes using video frames obtained from a low-cost webcam. The measurements are performed on human faces and the proposed algorithms were developed to be motion-tolerant. An interactive Stroop color word test is employed to induce stress on a set of twelve participants. We record the skin conductance and compare these responses to the stress curve assessed by a webcam-derived heart rate variability analysis. The results offer further support for the applicability of stress detection by remote and low-cost means, providing an alternative to conventional contact techniques. © 2013 ICST.

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