Local open‐ and closed‐loop manipulation of multiagent networks

The manipulation of networked cyberphysical devices via local external actuation or feedback control is explored, in the context of a canonical multiagent dynamical system that is engaged in a consensus or synchronization task. One main focus is to understand whether or not, and how easily, a stakeholder can manipulate the full network's dynamics by hijacking only one agent's actuation signal. Explicit spectral characterizations are given of the energy (effort) required to manipulate the dynamics. These characterizations are used to (1) gain structural insights into ease of manipulation, (2) show that manipulation along the consensus manifold is easy, and (3) address network design to enable or prevent manipulation. Additionally, it is shown that the multiagent system can be manipulated effectively along the consensus manifold using local feedback controls, which do not require model knowledge or wide‐area measurements.     

Influence of combined electromagnetohydrodynamics on microchannel flow with electrokinetic effect and interfacial slip

We investigate analytically the combined consequences of electromagnetohydrodynamic forces and interfacial slip on streaming potential mediated pressure-driven flow in a microchannel. Going beyond traditional Debye–Hückel limit, we first derive a closed-form analytical solution for velocity field by considering nonlinear electrical potential distribution, wall slip effects, externally imposed transverse magnetic field, and laterally applied electric field in the plane of flow. The effects of electrical double-layer (EDL) formation and the consequent interfacial phenomena are critically examined under such situations. An expression for induced streaming potential in the microchannel is deduced considering EDL formation and the consequences of finite conductance of the immobilized Stern layer. This simplified analytical expression is later on critically assessed against three-dimensional simulation paradigm of streaming potential mediated flows, which is a first effort of this kind. We demonstrate that flow rate increases progressively with increasing surface potential and eventually approaches to a limiting value. Combination of electromagnetohydrodynamic effect with liquid slip is shown to amplify the flow rate, even at lower values of surface potential. Our study brings out the possibility of achieving an optimum flow rate by judicious application of combined electromagnetohydrodynamics. The present analysis has significant consequence in the design of advanced microfluidic devices with improved efficiency and functionality.     

Robust RBF neural network–based backstepping controller for implantable cardiac pacemakers

Implantable cardiac pacemaker is a standard medical device to treat heart rhythm disorders. In this paper, a new adaptive backstepping controller is developed to enhance the performance of dual‐sensor pacemakers for regulating the heart rate based on radial basis function neural networks. The robust design of adaptive backstepping controller using Lyapunov functions allows to guarantee the stability and performance of the rate‐adaptive pacing system for accurately accomplishing the heart rate regulation at different preset or desired values. The developed control system has been successfully validated using 12 cases of the preset heart rates for 4 patients during 3 body activities, namely, at rest, walking, and jogging. The resulting root mean square error and maximum error are less than 0.9 and 1.7%, respectively. Moreover, the comparative results of this study showed that the performance of developed backstepping controller is superior to other pacemaker controllers in the previous studies. Therefore, it is potentially valid to be applied in dual‐sensor cardiac pacemakers for the clinical use.     

Biomaterial Based Polyurethane Adhesive for Bonding Rubber and Wood Joints

An intermediate compound for synthesizing polyester polyol was prepared from glycosylation of potato starch by reacting it with ethylene glycol in presence of sulphuric acid. Glycol glycoside thus prepared was characterized by HPLC and FTIR. This polyhydroxy compound was replaced in varying amounts with trimethylolpropane for polyester polyol synthesis. Sebacic acid was used as dicarboxylic acid along with castor oil for polyester polyol formulation. Polyols were reacted with toluene 2,4-diisocyanate adduct for polyurethane formation. Polyester polyol and polyurethane were characterized by FTIR. Polyurethane was utilized for bonding wood as well as rubber joints. Bond strength was measured by means of lap shear strength and peel strength for wood and rubber joints, respectively. Chemical resistance of polyurethane adhesive was also evaluated. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the Relation of Microstructure and Texture Evolution in an Austenitic Fe-28Mn-0.28C TWIP Steel During Cold Rolling

In the present study, microstructure and texture evolution in an austenitic Fe-28 wt pct Mn-0.28 wt pct C TWIP steel in the range between 10 and 80 pct reduction by cold rolling were systematically analyzed. The formation of the observed microstructural features occurred in three different stages: I (10 to 20 pct)—mainly slip lines, grain elongation, and formation of few twin-matrix lamellae; II (30 to 50 pct)—severe increase of the volume fraction of twins, alignment of twins with the rolling plane, and formation of microshear bands; and III (60 to 80 pct)—further alignment of twins, evolution of a herring bone structure, and macroshear bands. In contrast to most f.c.c. metals, the transition from Copper- to Brass-type texture occurred at low strain levels (30 pct). This behavior is attributed to the early formation of deformation twins in the material and can be related to the SFE of this high manganese steel. At higher reduction levels, microscopic (≥40 pct) and macroscopic shear band formation (≥60 pct) contributed to the increase of randomly oriented grains, mainly at the expense of the Brass component. Furthermore, the formation of the Goss component and of the 〈111〉//ND fiber (γ) is attributed to severe twin formation.     

Investigation on arc sound and metal transfer modes for on-line monitoring in pulsed gas metal arc welding

The arc sound was found to be strongly related to both process parameters and weld quality, like voltage and current signals, in gas metal arc welding. In this investigation, the acquired welding arc sound signal along with current and voltage signals were analyzed in time domain as well as frequency domain to correlate them with the various process parameters and metal transfer modes. The arc sound of continuous as well as pulsed gas metal arc welding at various process parameters was also compared. A major variation of auxiliary arc sound frequency peaks was observed due to change of pulse shape as evidenced by frequency domain analysis. The arc sound was also used to detect welding defects.     

A facile route to develop electrical conductivity with minimum possible multi‐wall carbon nanotube (MWCNT) loading in poly(methyl methacrylate)/MWCNT nanocomposites

Today, we stand at the threshold of exploring carbon nanotube (CNT) based conducting polymer nanocomposites as a new paradigm for the next generation multifunctional materials. However, irrespective of the reported methods of composite preparation, the use of CNTs in most polymer matrices to date has been limited by challenges in processing and insufficient dispersability of CNTs without chemical functionalization. Thus, development of an industrially feasible process for preparation of polymer/CNT conducting nanocomposites at very low CNT loading is essential prior to the commercialization of polymer/CNT nanocomposites. Here, we demonstrate a process technology that involves in situ bulk polymerization of methyl methacrylate monomer in the presence of multi‐wall carbon nanotubes (MWCNTs) and commercial poly(methyl methacrylate) (PMMA) beads, for the preparation of PMMA/MWCNT conducting nanocomposites with significantly lower (0.12 wt% MWCNT) percolation threshold than ever reported with unmodified commercial CNTs of similar qualities. Thus, a conductivity of 4.71 × 10^?5 and 2.04 × 10^?3 S cm^?1 was achieved in the PMMA/MWCNT nanocomposites through a homogeneous dispersion of 0.2 and 0.4 wt% CNT, respectively, selectively in the in situ polymerized PMMA region by using 70 wt% PMMA beads during the polymerization. At a constant CNT loading, the conductivity of the composites was increased with increasing weight percentage of PMMA beads, indicating the formation of a more continuous network structure of the CNTs in the PMMA matrix. Scanning and transmission electron microscopy studies revealed the dispersion of MWCNTs selectively in the in situ polymerized PMMA phase of the nanocomposites. Copyright © 2012 Society of Chemical Industry     

Numerical investigation of wall heat conduction effects on catalytic combustion in split and continuous monolith tubes

The optimum length of a monolith tube is one for which near-hundred percent conversion is attained, and at the same time, the catalyst over the entire length of the tube is utilized. In practice, the length is adjusted by stacking monolith plugs end-to-end. In this study, the repercussions of such a practice are investigated numerically with the goal to determine if a tube of length 2L demonstrates the same behavior as two tubes of length L each, stacked end-to-end. Catalytic combustion of methane–air mixture on a platinum catalyst is considered. The studies are conducted using a multi-step reaction mechanism involving 24 surface reactions between 19 species. Two different materials are considered for the walls of the monolith tube, namely silicon carbide and cordierite. Both steady state and transient simulations are performed. Results indicate that the ignition and blowout limits can be significantly different between split and continuous tubes when the wall is made up of a high thermal conductivity material, such as silicon carbide. For steady state combustion, for both wall materials, the point of attachment of the flame to the wall is altered by splitting the tube—the effect being more pronounced for silicon carbide and at relatively high Reynolds numbers. These results imply that axial heat conduction, or lack thereof due to thermal contact resistance, through the walls of the monolith results in thermal non-equilibrium between the solid and fluid phase, and subsequently affects ignition and flame stability in catalytic combustion.