Cost-Based Filtering Techniques for Stochastic Inventory Control Under Service Level Constraints

This paper¹ considers a single product and a single stocking location production/inventory control problem given a non-stationary stochastic demand. Under a widely-used control policy for this type of inventory system, the objective is to find the optimal number of replenishments, their timings and their respective order-up-to-levels that meet customer demands to a required service level. We extend a known CP approach for this problem using three cost-based filtering methods. Our approach can solve to optimality instances of realistic size much more efficiently than previous approaches, often with no search effort at all. This work was supported by Science Foundation Ireland under Grant No. 03/CE3/I405 as part of the Centre for Telecommunications Value-Chain-Driven Research (CTVR) and Grant No. 00/PI.1/C075. ¹This paper is an extended version of [19].     

A C5 parallel robot identification and control

The paper proposes a controller scheme based on a priori identification for a C5 parallel robot. First we realize the identification of dynamic parameters of the robot using the Least Squares technique. Different data are used for this step of identification. The cross validation permitted to select and confirm the identified parameters. After, a control scheme (computed torque) is applied to control the C5 parallel robot. The functions of this control scheme are based on precedent identified parameters. In order to reduce the effect of the identification error, we have added a robustness term based on sliding mode technique. The stability of the system in closed loop is presented using the Lyapunov principle. Experimental results of identification and control are presented and show the effectiveness of our methodology.     

Throughput analysis and bandwidth allocation for IEEE 802.11 WLAN with hidden terminals

Motivated by observations from real world wireless local area network (WLAN) deployments, we develop in this paper a novel analytical model to characterize the saturation throughput of an IEEE 802.11-based access point (AP) and stations under the influence of hidden terminals. Unlike existing models, our model can accommodate different numbers of hidden nodes without increasing the model complexity. Given any number of hidden nodes, only four constraints are needed to describe the interaction between stations and the AP with the consideration of both uplink and downlink traffic. Simulation evaluation shows that our model predicts network performance accurately over a wide range of network sizes and indicates the existence of a throughput starvation problem. To address this problem, based on our model, we formulate a bandwidth allocation problem to optimize the network throughput and fairness under some predefined requirements by systematically tuning the AP and stations contention windows. Simulation results show that the starvation problem is resolved with our approach, and the target throughput is met.     

A two-phase framework for quality-aware Web service selection

Service-oriented computing is gaining momentum as the next technological tool to leverage the huge investments in Web application development. The expected large number of Web services poses a set of new challenges for efficiently accessing these services. We propose an integrated service query framework that facilitates users in accessing their desired services. The framework incorporates a service query model and a two-phase optimization strategy. The query model defines service communities that are used to organize the large and heterogeneous service space. The service communities allow users to use declarative queries to retrieve their desired services without worrying about the underlying technical details. The two-phase optimization strategy automatically generates feasible service execution plans and selects the plan with the best user-desired quality. In particular, we present an evolutionary algorithm that is able to “co-evolve” multiple feasible execution plans simultaneously and allows them to compete with each other to generate the best plan. We conduct a set of experiments to assess the performance of the proposed algorithms.     

Existence of optimal controls for systems driven by FBSDEs

We prove the existence of optimal relaxed controls as well as strict optimal controls for systems governed by non linear forward-backward stochastic differential equations (FBSDEs). Our approach is based on weak convergence techniques for the associated FBSDEs in the Jakubowski S-topology and a suitable Skorokhod representation theorem.     

The pleural thickening approximation from thoracic CT scans

Multimedia Tools and Applications - The involvement of medical imaging in medical procedures plays an important role in the diagnosis and planning of a therapeutic treatment. Computerized...