Toward enhanced wireless coexistence in ISM band via temporal characterization and modelling of 802.11b/g/n networks

This paper presents extensive experimental characterization and empirical modelling of 802.11 temporal behavior. A detailed characterization of 802.11b/g/n homogeneous and heterogeneous network traffic patterns is featured, including idle time distribution and channel utilization. A complete modelling of 802.11 networks in the 2.4 GHz Industrial, Scientific, and Medical band is also presented. Such information can assist the development of other wireless technologies aiming to utilize the crowded Industrial, Scientific, and Medical band more efficiently and to achieve enhanced wireless coexistence. In this work, models are derived for both homogeneous and heterogeneous 802.11 network idle time distributions. Also presented is a case study utilizing 802.15.4 ZigBee transmitter packet size that was adaptively modified based on channel idle time distribution. Results demonstrate superior ZigBee performance and significant enhancement in throughput. Copyright © 2016 John Wiley & Sons, Ltd.     

Agent-Based Simulation and Microstructure Modeling of Immature Stock Markets

This work presents an artificial order-driven market able to reproduce mature and immature stock markets properties in the case of a single traded asset. This agent-based artificial market is designed to simulate characteristics of immature stock markets (high risk and low efficiency) by reproducing their stylized facts related mainly to information asymmetry and herd behavior. These two properties are modeled by combining social network and multi-agent simulations. The constructed scale-free social network, linking the modeled investors, gives rise to both informed and uninformed agents communities. Different assortative topologies are proposed and linked to different degrees of information asymmetry and market maturities. Several simulation experiments show that the modeled information asymmetry and herd behavior succeed in reproducing artificially some important stylized facts characterizing differences between immature and mature stock markets.     

Watermark location via back-lighting and recto removal

We consider the problem of locating a watermark in pages of archaic documents that have been both scanned and back-lit: the problem is of interest to codicologists in identifying and tracking paper materials. Commonly, documents of interest are worn or damaged, and all information is victim to very unfavourable signal-to-noise ratios—this is especially true of ‘hidden’ data such as watermarks and chain lines. We present an approach to recto removal, followed by highlighting of such ‘hidden’ data. The result is still of very low signal quality, and we also present a statistical approach to locate watermarks from a known lexicon of fragments. Results are presented from a comprehensively scanned nineteenth century copy of the Qur’ān. The approach has lent itself to immediate exploitation in improving known watermarks, and distinguishing between twin copies. Mr Hiary was supported by the University of Jordan in pursuing this work.     

Properties and microstructural aspects of TiO2‐doped sintered Alumina‐Zirconia composite ceramics

The effect of titania content on the densification, the phase transformation, the microstructures, and mechanical properties of 50 wt% Al₂O₃‐50 wt% ZrO₂ (12 mol% CeO₂) was evaluated. Ceramic composites with different TiO₂ content (0.27, 5, 10 wt%) were prepared by pressureless sintering at low temperature (1400°C) for 2 hours in air. Dense ceramic was obtained by adding 5 wt% of TiO₂ loading to improved mechanical properties. The microstructure analysis provided lots of information about solid‐state reactivity in alumina‐zirconia‐titania ternary system. The content of TiO₂ strongly affected the phases evolution and the grain growth during sintering. Furthermore, a significant effect on mechanical properties and fracture behavior was also observed.     

The effect of ion slip on the flow of Reiner-Rivlin fluid due a rotating disk with heat transfer

The magnetohydrodynamic rotating disk flow and heat transfer of a non-Newtonian Reiner-Rivlin conducting fluid is studied considering the ion slip. The governing nonlinear equations are solved numerically using finite differences. The results show that the inclusion of the ion slip and the non-Newtonian fluid characteristics have interesting effects on the velocity and temperature distributions.     

The effect of suction and injection on unsteady flow of a dusty conducting fluid in rectangular channel

In the present study, the unsteady Hartmann flow of a dusty viscous incompressible electrically conducting fluid under the influence of an exponentially decreasing pressure gradient is studied without neglecting the ion slip. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below. The fluid is acted upon by an external uniform magnetic field which is applied perpendicular to the plates. An analytical solution for the governing equations of motion is obtained to yield the velocity distributions for both the fluid and dust particles.     

Dynamics of the macpherson strut motor-vehicle suspension system in point and joint coordinates

In this paper the dynamic analysis of the Macpherson strut motor-vehicle suspension system is presented. The equations of motion are formulated using a two-step transformation. Initially, the equations of motion are derived for a dynamically equivalent constrained system of particles that replaces the rigid bodies by applying Newton’s second law. The equations of motion are then transformed to a reduced set in terms of the relative joint variables. Use of both Cartesian and joint variables produces an efficient set of equations without loss of generality. For open chains, this process automatically eliminates all of the non-working constraint forces and leads to an efficient solution and integration of the equations of motion. For closed loops, suitable joints should be cut and few cut-joints constraint equations should be included for each closed chain. The chosen suspension includes open and closed loops with quarter-car model. The results of the simulation indicate the simplicity and generality of the dynamic formulation.     

Hydromagnetic flow and heat transfer above a rotating disk with suction or injection considering hall effect

The steady hydromagnetic flow of a conducting fluid above a rotating disk is studied with heat transfer in the presence of uniform suction or injection without neglecting the Hall effect. The governing momentum and energy equations are solved numerically using finite differences. The results show that the inclusion of the Hall current together with the suction or injection velocity has important effects on the velocity and temperature fields.     

Numerical kinematic analysis of the standard macpherson motor-vehicle suspension system

In this paper, an efficient numerical algorithm for the kinematic analysis of the standard MacPherson suspension system is presented. The kinematic analysis of the suspension mechanism is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and at the kinematic joints. Geometric constraints that fix the distances between the points belonging to the same rigid link are introduced. The nonlinear constraint equations are solved by iterative numerical methods. The corresponding linear equations of the velocity and acceleration are solved to yield the velocities and accelerations of the unknown points. The velocities and accelerations of other points of interest as well as the angular velocity and acceleration of any link in the mechanism can be calculated.     

Performance of a backpropagation trained feedforward network on an MIMD architecture

Training of feedforward networks on sequential machines is a computationally expensive process. This has motivated the implementation of parallel versions of the backpropagation training algorithm on different parallel platforms in order to decrease the processing time required for training. In this paper, we are investigating the implementation of backpropagation on the Alex AVX-2 coarse-grained MIMD machine. A master–slave parallel implementation is carried out for the encoder–decoder benchmark problem. A communication model for the broadcasting/gathering is used to study the effect of using different topologies. Then the performance of the backpropagation algorithms is analyzed for different network sizes and numbers of processors when the nodes are arranged as a pipeline array and in a mesh topology. © 1998 John Wiley & Sons, Ltd.