A CP framework for testing CP

The success of several constraint-based modeling languages such as OPL, ZINC or COMET, appeals for better software engineering practices, particularly in the testing phase. This paper introduces a testing framework enabling automated test case generation for constraint programming. We propose a general framework of constraint program development which supposes that a first declarative and simple constraint model is available from the problem specifications analysis. Then, this model is refined using classical techniques such as constraint reformulation, surrogate, redundant, implied, global constraint and symmetry-breaking to form an improved constraint model that must be thoroughly tested before being used to address real-sized problems. We think that most of the faults are introduced in this refinement step and propose a process which takes the first declarative model as an oracle for detecting non-conformities and derive practical test purposes from this process. We implemented this approach in a new tool called CPTEST that was used to automatically detect non-conformities on classical benchmark programs, such as the Golomb rulers, n-queens, social golfer and the car-sequencing problems.     

Self-stabilizing algorithm for high service availability in spite of concurrent topology changes in ad hoc mobile networks

Mobile nodes in ad hoc networks move freely and run out of battery power so quickly, which leads to frequent network partitioning. Network partitioning considerably reduces service availability when the server node is not in the same partition as the client nodes. In order to provide a continuous service availability for all mobile nodes, we propose a self-stabilizing algorithm that can tolerate multiple concurrent topological changes and can incur a cost of one server per long-lived connected component. By using (1) the time interval-based computations concept that distinguishes between disjoint and concurrent computations, and (2) Markov chain model, the proposed algorithm can within a finite time converge to a legitimate state even if topological changes occur during the convergence time. Our simulation results show that the algorithm can ensure very high service availability, and each node has a strong path to the server of its network component over 98% of the time.     

Efficient data aggregation with in-network integrity control for WSN

Energy is a scarce resource in Wireless Sensor Networks (WSN). Some studies show that more than 70% of energy is consumed in data transmission in WSN. Since most of the time, the sensed information is redundant due to geographically collocated sensors, most of this energy can be saved through data aggregation. Furthermore, data aggregation improves bandwidth usage and reduces collisions due to interference. Unfortunately, while aggregation eliminates redundancy, it makes data integrity verification more complicated since the received data is unique.     

Modeling and solving a one-supplier multi-vehicle production-inventory-distribution problem with clustered retailers

This paper considers a supply chain management problem which integrates production, inventory, and distribution decisions. The supply chain is composed of one supplier production facility and several retailers located in a given geographic region. The supplier is responsible for the production and the replenishment of the inventory of retailers, in a vendor managed inventory (VMI) context. The distance between retailers is negligible compared to the distance between the supplier and the retailers’ region. Thus, for each vehicle, there is a major fixed cost for traveling to the cluster of retailers and a minor fixed cost for visiting each individual retailer. The problem consists of determining quantities to be produced, quantities to be delivered to retailers, vehicles to be used, and retailers to be serviced by each vehicle. This problem is an extension of the one warehouse multi-retailer problem with the consideration of production planning and storage and vehicle capacity limitations in addition to fixed vehicle utilization costs and retailer servicing costs. The objective is to minimize a total cost composed of production, transportation, and inventory holding costs at the supplier and at the retailers. Two mixed integer linear programming formulations are proposed and six families of valid inequalities are added to strengthen these formulations. Two of these families are new and the others are adapted from the literature. The numerical results show that the valid inequalities considerably improve the quality of the formulations. Moreover, the parameters that influence the most computational times are analyzed.     

On eliminating packet droppers in MANET: A modular solution

In this paper we deal with misbehaving nodes in mobile ad hoc networks (MANETs) that drop packets supposed to be relayed, whose purpose may be either saving their resources or launching a DoS attack. We propose a new solution to monitor, detect, and safely isolate such misbehaving nodes, structured around five modules: (i) The monitor, responsible for controlling the forwarding of packets, (ii) the detector, which is in charge of detecting the misbehaving of monitored nodes, (iii) the isolator, basically responsible for isolating misbehaving nodes detected by the detector, (iv) the investigator, which investigates accusations before testifying when the node has not enough experience with the accused, and (v) finally the witness module that responds to witness requests of the isolator. These modules are based on new approaches, aiming at improving the efficiency in detecting and isolating misbehaving nodes with a minimum overhead. We describe these modules in details, and their interactions as well. We also mathematically analyze our solution and assess its performance by simulation, and compare it with the watchdog, which is a monitoring technique employed by almost all the current solutions.     

Influence des fumées de silice sur l’évolution de l’hydratation des pâtes de chaux ou de Ciment Portland

The silica fume (SF) is used in civil engineering, in particular for the manufacture of high performance concrete.In order to better understand the gain in strength of the concretes containing SF, the microstructural aspect has been examined.Mixtures of SF–Lime pastes present a hydraulic setting which is due to the formation of a C–S–H phase (calcium silicate hydrate). The latter is semi-crystallized. It is characterized by the lines of X-ray diffraction, hk0 such as: 3,06 Å (220), 2,80 Å (400) and 1,83 Å (040).The mix design SF–Lime paste is thus a simplified approach of that of the mixtures SF–OPC in which the main reaction is the fixation, by the SF, of lime coming from the hydration of C₃S in the form of C–S–H.Tests have been carried out on two varieties of SF resulting from the same furnace with the presence of lime or Portland cement. The results show that the presence of certain impurities, by their actions on the solubility of silica plays a significant role on the evolution of the hydration of the principal components of Portland cements and the kinetics of lime fixation by the SF.Among the impurities contained in the SF, carbon delays considerably the hydration of the principal components of Portland cement (C₃S and C₃A) as well as the pozzolanic reactivity of the silica fume without removing it.     

A nonconforming finite element method¶with anisotropic mesh grading¶for the incompressible Navier–Stokes equations¶in domains with edges

Any solution of the incompressible Navier–Stokes equations in three-dimensional domains with edges has anisotropic singular behaviour which is treated numerically by using anisotropic finite element meshes. The velocity is approximated by Crouzeix–Raviart (nonconforming 𝒫₁) elements and the pressure by piecewise constants. This method is stable for general meshes since the inf-sup condition is satisfied without minimal or maximal angle condition. The existence of solutions to the discrete problems follows. Consistency error estimates for the divergence equation are obtained for anisotropic tensor product meshes. As applications, the consistency error estimate for the Navier–Stokes solution and some discrete Sobolev inequalities are derived on such meshes. These last results provide optimal error estimates in the uniqueness case by the use of appropriately refined anisotropic tensor product meshes, namely, if N _e is the number of elements of the mesh, we prove that the optimal order of convergence h∼ N _e ^{− 1/3}. Received:July 2001 / Accepted: July 2002     

Une nouvelle architecture de gestion de réseaux DiffServ basée sur la technologie de réseau actif et la gestion à base de règles

The objective of this work is to propose an architectural solution to the very complex problem of DiffServ network management and control. Despite the fact that DiffServ offers a scalable QoS provisioning solution, it introduces a high complexity in term of its deployment due to the number of complex configurations to perform in the highly distributed and heterogeneous network environment. The proposed solution aims to take benefit from the scalability and flexibility properties of Active Network technology for distributing the control in large scale as well as the autonomic property of Policy Based Management to automate the distribution of these tasks in the operator network. This solution constitutes an alternative to the client/server approach generally used.     

Balancing the tradeoffs between scalability and availability in mobile ad hoc networks with a flat hashing-based location service

In this paper, we propose FSLS (Flat-based Some-for-some Location Service), a new location service for ad hoc mobile networks. The location service is based on the hash-based sets system that can offer a high location information availability. The network area is divided into non-overlapping zones. A node identifier is mapped to a set of home zones, each of which contains a unique location server, which makes FSLS works as a some-for-some approach. Using cross-layer design, the service can tolerate server mobility and server failures, and last for a long time period. We analyze FSLS and six other existing location services. The theoretical analysis as well as simulation results show that FSLS offers a good trade-off between location availability and scalability. It comes second after a quorum-based location service in terms of location availability and it is the closest competitor to a hierarchical location service in terms of scalability.