Discrete Time Sliding Mode Controller Using a Disturbance Compensator for Nonlinear Uncertain Systems

International Journal of Control, Automation and Systems - In this paper, we propose a new sliding mode control for discrete time nonlinear uncertain systems. The uncertainties include both...     

Numerical simulation of viscous fingering of shear‐thinning fluids

The viscous fingering instability of miscible shear‐thinning fluids has been examined using a pseudo‐spectral numerical technique based on the Hartley transform. The instability was studied for a flow in a rectilinear Hele‐Shaw cell, and the shear‐thinning character of the fluids has been modelied using the Carreau equation. New mechanisms of viscous fingering not previously observed in the case of similar Newtonian flow displacements have been identified. These mechanisms, which are reminiscent of the fractal patterns observed in experimental studies, were interpreted in terms of the velocity‐dependent mobility of the flow.     

Rheology of fiber filled polymer melts: Role of fiber‐fiber interactions and polymer‐fiber coupling

An experimental study and a numerical modeling analysis are carried out to examine the effects of fiber‐fiber interactions and coupling between fiber orientation and polymer chains conformation on the rheological properties of fiber suspensions. The experimental study allowed examination of large fiber volume fractions up to 35% over a range of shear rates that spans eight decades. This study confirmed already known results and led to new ones. In particular, a peak in the steady shear viscosity at the low shear rate region is observed at large volume fractions. Furthermore, new results regarding the applicability of the Cox‐Merz rule, the behavior of the damping factor, and the end pressure drops are reported, and physical interpretations are proposed. The results of the numerical modeling showed that it is necessary to account for the polymer‐fiber coupling factor to obtain a good fit between the model predictions and the experimental measurements. Comparisons between the model predictions and the experimental measurements allowed study of the variation of the parameters that govern the fiber‐fiber interactions and the polymer‐fiber coupling with the properties of the suspension and the flow. POLYM. ENG. SCI., 45:385–399, 2005. © 2005 Society of Plastics Engineers     

Coalitional game‐based behavior analysis for spectrum access in cognitive radios

The core of cognitive radio paradigm is to introduce cognitive devices able to opportunistically access the licensed radio bands. The coexistence of licensed and unlicensed users prescribes an effective spectrum hole‐detection and a non‐interfering sharing of those frequencies. Collaborative resource allocation and spectrum information exchange are required but often costly in terms of energy and delay. In this paper, each secondary user (SU) can achieve spectrum sensing and data transmission through a coalitional game‐based mechanism. SUs are called upon to report their sensing results to the elected coalition head, which properly decides on the channel state and the transmitter in each time slot according to a proposed algorithm. The goal of this paper is to provide a more holistic view on the spectrum and enhance the cognitive system performance through SUs behavior analysis. We formulate the problem as a coalitional game in partition form with non‐transferable utility, and we investigate on the impact of both coalition formation and the combining reports costs. We discuss the Nash Equilibrium solution for our coalitional game and propose a distributed strategic learning algorithm to illustrate a concrete case of coalition formation and the SUs competitive and cooperative behaviors inter‐coalitions and intra‐coalitions. We show through simulations that cognitive network performances, the energy consumption and transmission delay, improve evidently with the proposed scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

Two‐sided matching framework for optimal user association in 5G multi‐RAT UDNs

Recently, academic and industrial research communities are paying more explicit attention to the 5G multiple radio access technology ultra‐dense networks (5G multi‐RAT UDNs) for boosting network capacity, especially in UD urban zones. To this aim, in this paper, we intend to tackle the user association problem in 5G multi‐RAT UDNs. By considering the decoupled uplink/downlink access (DUDA), we divide our user association problem into two distinct subproblems representing, respectively, the uplink and the downlink channels. Next, we formulated each one as a nonlinear optimization problem with binary variables. Then, to solve them, we were restricted by the hard complexity, as well as the hard feasibility of centralized user association schemes. Thus, to resolve our user association problem in a reasonable time and distributed manner, we formulated each subproblem as a many‐to‐one matching game based on matching theory. Next, we provide two fully distributed association algorithms to compute the uplink and downlink stable matching among user equipments (UEs) and base stations (BSs). Simulation results corroborate our theoretical model and show the effectiveness and improvement of our achieved results in terms of the overall network performance, quality of service (QoS), and energy efficiency (EE) of UEs.     

The KNNs Safe Region Pruning Based Method: An Efficient Approach for Continuously Determining the k Nearest Ambulances in Emergency

Wireless Personal Communications - A lot of research has been done on the problem of finding the k nearest neighbor to a query point. Existing studies are usually intended to work on static data....     

Towards a classification of energy aware MAC protocols for wireless sensor networks

Power management is an important issue in wireless sensor networks (WSNs) because wireless sensor nodes are usually battery powered, and an efficient use of the available battery power becomes an important concern specially for those applications where the system is expected to operate for long durations. This necessity for energy efficient operation of a WSN has prompted the development of new protocols in all layers of the communication stack. Provided that, the radio transceiver is the most power consuming component of a typical sensor node, large gains can be achieved at the link layer where the medium access control (MAC) protocol controls the usage of the radio transceiver unit. MAC protocols for sensor networks differ greatly from typical wireless networks access protocols in many issues. MAC protocols for sensor networks must have built‐in power conservation, mobility management, and failure recovery strategies. Furthermore, sensor MAC protocols should make performance trade‐off between latency and throughput for a reduction in energy consumption to maximize the lifetime of the network. This is in general achieved through duty cycling the radio transceiver. Many MAC protocols with different objectives were proposed for wireless sensor networks in the literature. Most of these protocols take into account the energy efficiency as a main objective. There is much more innovative work should be done at the MAC layer to address the hard unsolved problems. In this paper, we first outline and discuss the specific requirements and design trade‐offs of a typical wireless sensor MAC protocol by describing the properties of WSN that affect the design of MAC layer protocols. Then, a typical collection of wireless sensor MAC protocols presented in the literature are surveyed, classified, and described emphasizing their advantages and disadvantages whenever possible. Finally, we present research directions and identify open issues for future medium access research. Copyright © 2009 John Wiley & Sons, Ltd.     

Lignin liquefaction under microwave heating

Organosolv lignin from olive tree pruning was subjected to liquefaction under microwave heating and modifying the experimental conditions (time, temperature, and concentration of catalyst) according to an experimental design. The organosolv lignin and obtained polyols were characterized using attenuated‐total reflection infrared spectroscopy (ATR‐IR), thermogravimetric analysis (TGA), gel permeation chromatography, and another parameter such as the hydroxyl number (I_OH). The ATR‐IR and the TGA results showed that the solvents (polyethylene glycol #400 and glycerol) reacted with the lignin being present in the final product. The optimal polyol showed a liquefaction yield of 99.07% that was obtained in 5 min of reaction at 155°C with 1% of sulphuric acid. The liquefaction product showed a hydroxyl number of 811.8 mg KOH/g, suitable to be used as a precursor in polyurethane foam synthesis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3292–3298, 2013     

Signaling game approach to improve the MAC protocol in the underwater wireless sensor networks

Underwater sensor networks (UWSNs) are instructed for critical applications like military surveillance and underwater oil spills that conducted in a very massive three‐dimensional (3‐D) space that needs many underwater nodes (UNs) to cover the target area. Those UNs are not easy to recharge and cannot exploit solar power. MAC protocols deployed for UWSN ought to consider the energy efficiency, so as, to extend the network lifetime with total connectivity and significant throughput. Terrestrial MAC protocols could not be used for UWSN due to long and unpredictable propagation delay. Consequently, the development of a new MAC protocol for the harsh environment as underwater is a challenging task. In this study, we focus on the deployment of TDMA in UWSN for this, two schemes entitled TDMA slot sharing (TSS) and free time slots reallocation (FTSR) are proposed. Received data stored in the buffer waiting for processing and forwarding might lead to an unlimited data transfer latency those results in the buffer overflow. Otherwise, free time slots appearing during the communication process resulting from dead nodes increase uselessly sleep time for the rest of the nodes. Both schemes based on signaling game are proposed to overcome those problems, TSS is used to enable the slot sharing between UNs during the communication process to reduce the buffer overflow. FTSR scheme aims to increase the throughput of UNs by allowing the reuse of free time slots. Numerical results conducted in this work show good improvement in the network performance concerning throughput.     

Optimization of hot-dip galvanizing process of reactive steels: Minimizing zinc consumption without alloy additions

One of the problems encountered when galvanizing reactive steel is the thickness of the zinc layer. The aim of this paper is to apply Doehlert design taking into account the effects of the bath temperature, the immersion time and the withdrawal speed in order to obtain a reduction of the zinc consumption. Our results showed that there is a serious opportunity to optimize the galvanizing process at a minimum thickness playing only on the physical parameters and without resorting to any addition.