MobileJMS: une solution globale d’adaptation des applications nomades

Middleware technologies have emerged as a key element of future mobile systems. In this paper, we argue that Message Oriented Middleware Systems (MOMS) provides a valuable solution to nomadic environment issues. They are characterized by a communication style allowing a strong decoupling between distributed entities. The first part describes MobileJMS, a mom system characterized by communication adaptability and context-awareness. Its communication module is based on components which can be plugged and configured dynamically to deal with various events such as bandwidth variation or frequent disconnections. The second part is related to an overall adaptation model that makes adaptation decisions by considering user preferences, application requirements and execution context state. The key function of the model is the selection of the most appropriate policy to the current context.     

Efficient Analysis of Vertical Projection Histogram to Segment Arabic Handwritten Characters

The paper discusses the segmentation of words into characters, which is an essential task in the development process of character recognition systems, as poorly segmented characters will automatically be unrecognized. The segmentation of offline handwritten Arabic text poses a greater challenge because of its cursive nature and different writing styles. In this article, we propose a new approach to segment handwritten Arabic characters using an efficient analysis of the vertical projection histogram. Our approach was tested using a set of handwritten Arabic words from the IFN/ENIT database, and promising results were obtained.     

Improved version of the McMurtry-Fu reinforcement learning scheme

An improved version of the reinforcement scheme originally developed by McMurtry and Fu is presented. A projection procedure as well as a regularizing parameter are introduced to ensure the probability measure and uniqueness of the solution. To prevent degenerate situations where the realization of the function to be optimized is equal to zero, an auxiliary strictly positive regularizing parameter is introduced. A vector representation and a convergence analysis of this multimodal one-dimensional search technique are derived on the basis of the traditional convergence results on Robbins-Monro type of stochastic algorithms. Global maximization and minimization problems are discussed. Finally, some simulation results illustrate the performance and the feasibility of this self-learning optimization algorithm.     

Tunable SIW bandpass filter-combined microstrip antenna based on liquid crystals

In this paper, the design and experimental characterization of a novel tunable Substrate Integrated Waveguide (SIW) filter and tunable microstrip patch antenna in multilayer technology based on liquid crystals (LCs) are presented. To realize the concept, the SIW filter and patch antenna are combined directly coupled by T-slot at the middle of the common ground plane. Due to their flexibility as a liquid dielectric and because of their anisotropic characteristics, they have been used widely in telecommunication devises, display technologies, and RF and microwave devices. The dielectric proprieties of LCs are controlled through the strength of the bias voltage of 15 V, a return loss (S₁₁) better than ?35 dB with a global bandwidth of around 425 MHz (18%) and a frequency agility of 13.75%, are demonstrated. A good agreement is noticed between the simulated and the measured data.     

Optimizing the throughput‐lifetime tradeoff in wireless sensor networks with link scheduling,rate adaptation,and power control

Throughput and lifetime are usually conflicting objectives in designing wireless sensor networks; hence, the right balance needs to be found. With this aim in view, we address in this paper the problem of minimizing the frame length defined within a time division multiple access scheme and the problem of maximizing network lifetime subject to a maximum frame length. The pursued solution in either case leverages a wide range of parameters related to coverage, routing, transmission power, and data rate. Furthermore, it is consistent with the physical interference model. To this end, we rely on column generation technique to derive near‐optimal solutions even when the integrality constraints on coverage and flow variables are enforced. Moreover, we propose a polynomial‐time heuristic algorithm to solve efficiently the underlying NP‐hard problem of concurrent link selection with discrete power control and rate adaptation. Simulation results show that our heuristic algorithm leads to solutions within 3% of optimality while saving around 99% of computation time. Besides, the results illustrate the significant impact of power control and rate adaptation on throughput and lifetime improvement. Interestingly, we found that network lifetime can be significantly prolonged when traffic demands are sufficiently low at the affordable cost of small decrease in throughput. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous determination of in-plane shear and transverse moduli of unidirectional composite laminae at different strain rates and temperatures

A semi-empirical method is proposed for the extraction, simultaneously, of the transverse tensile and in-plane shear moduli of unidirectional laminae, at various strain rates and temperatures, from tests on symmetric and balanced ±65 ° angle-ply composite laminates. The extraction method is applied to data obtained from tests on Kevlar-49/epoxy and carbon/ epoxy filament-wound tubes which were subjected to internal pressure loading at three key temperatures of −45, 20 and 70 °C at different strain rates of up to 80/s. The combined effect of strain rate and temperature on these extracted properties is studied by applying strain rate temperature equivalence principles. It is found that the variation of the mechanical properties of the two materials with strain rate and temperature can be adequately described by semi-empirical equations similar to the Arrhenius and Williams-Landel-Ferry relationships, usually used for homogeneous solids.     

CAD-based cost calculation of mould cavities

This article introduces a method for generating and analyzing CAD models of mould cavities to compute the tool accessibility. Using information about the surface curvature, a determination of working areas for different milling head geometries becomes possible. Relating groups of surfaces with milling heads and specific cutting data allows calculating the manufacturing time of roughing and finishing operations, including the tool change time. Determining the working areas, inaccessible for milling heads, enables to estimate the volume of material that needs to be eroded. A CAD-based application of the calculation tool `Visual Form Calculator’ (VFC), developed at IFW, is presented. Using the VFC, companies of the tool and form making industry are able to generate a virtual model of the contour element in order to analyze the accessibility of the working areas of the cavity and calculate manufacturing costs.     

Neuro-fuzzy modelling of power plant flue-gas emissions

This paper concerns process modelling using fuzzy neural networks. In distributed logic processors (DLP) the rule base is parameterised. The DLP derivatives required by gradient-based training methods are given, and the recursive prediction error method is used to adjust the model parameters. The power of the approach is illustrated with a modelling example where NO_x-emission data from a full-scale fluidised-bed combustion district heating plant are used. The method presented in this paper is general, and can be applied to other complex processes as well.     

Assessing mould costs analysing manufacturing processes of cavities

Pressure die casting mould manufacturing companies have difficulties assessing manufacturing costs for bid generation. In particular, manufacturing effort of mould cavities could hardly be predicted accurately. Due to varying complexity of casting part geometry, processing time of manufacturing cavities appears to be a rather unpredictable factor influencing costs calculation of moulds. This article introduces a novel method for generating and analysing computer-aided design (CAD) models of mould cavities to compute the tool accessibility. Using geometrical information of cavities, working areas for different milling head geometries are determined, and processing times are calculated. Thereupon, a three-step accessibility analysis (AA) has been conducted. Beside the AA method, a CAD-based application of the calculation tool ??visual form calculator?? (VFC), developed at IFW, is presented. Using the VFC, companies are now able to generate a virtual model of the contour element in order to assess mould costs accurately when analysing manufacturing processes of cavities.     

Residual Stress Assessment in Thin Angle Ply Tubes

This preliminary study aims to investigate the residual stresses developed in hot cured thin-walled angle-ply filament wound tubes made of E-glass/epoxy, Kevlar/epoxy and carbon/epoxy materials. The residual stresses were estimated from change in geometry of these tubes when axially slitted at ambient temperature. Three basic deformation modes; namely opening up, closing-in and twisting, were observed and these depended on the winding angle, material and wall thickness. The residual stresses were also determined from hoop and axial strain gauges mounted on both the inner and outer surfaces at various locations around the tube. The stresses were compared with theoretical prediction based upon a linear thermo-elastic analysis. Both the predicted and measured values were found to increase with increasing hoop stiffness but there was a large discrepancy between the predicted and measured data, reaching a factor of 5 for the thinnest case. When compared with predicted failure stresses, the experimentally determined stresses were some 15% of the computed compressive strength.