Set-up games: a heuristic game-theoretic approach to set-up decisions for heterarchical manufacturing systems

Heterarchical control systems have emerged as promising alternatives to conventional centralized and hierarchical shop floor control systems. However, research to date has largely ignored long-term control issues such as the timing of resource reconfigurations, which are vital for the avoidance of myopic decision-making. As traditional analysis techniques implicitly assume centralized analysis and implementation of policies, they are not directly applicable to heterarchical environments. A non-cooperative game-theoretic planning technique for autonomous analyses of reconfiguration decisions by heterarchical machine controllers is described. Under the proposed system, a machine controller evaluates a set-up game to determine appropriate actions when faced with a sequence-independent reconfiguration decision. The prescribed action is defined by a pure or mixed-strategy equilibrium of the set-up game. By evaluating a game, the machine controller accounts for the potential actions and reactions of other machine controllers in the system. The approach allows the autonomous machine controller to make set-up decisions about future actions while preserving the independence characteristic of controllers in heterarchical environments.     

Singularities in cylindrical vector beams

Cylindrical vector beams with azimuthal and radial polarization distributions are studied for singularities. It is shown experimentally that these beams have screw dislocation as well as edge dislocation at the same time. The relation between phase and polarization of light beam is the key to understand this fact. We envisage that this has potential application in phase synthesis using polarization engineering. Further, the polarization singularities in these inhomogeneously polarized beams are examined by measuring Stokes parameters across the cross-section of these beams.     

Development and physico‐mechanical behavior of LDPE–sisal prepreg‐based composites

Low‐density polyethylene (LDPE)‐coated sisal fiber prepreg was prepared by using solution coating process. These coated fiber prepregs were consolidated to make composites having different weight fraction of sisal fibers in a hot compression‐molding machine. This experimental study reveals that higher loading of sisal fiber up to 57wt% in LDPE–sisal composites is possible by this technique. Mechanical and abrasive wear characteristics of these composites were determined. The tensile strength of composites increased with the increase in sisal fiber concentration. Coating thickness of LDPE was varied by changing the viscosity of LDPE–xylene solution that manifested to different weight fraction of fiber in sisal–LDPE composites. Mechanical, dynamic mechanical, and abrasive wear characteristics of these composites were determined. The tensile strength and modulus of sisal composites reached to 17.4 and 265 MPa, respectively, as compared to 7.1 and 33MPa of LDPE. Storage modulus of sisal composites LD57 reached to 2.7 × 10⁹ MPa at 40°C as compared to 8.1 × 10⁸ MPa of LDPE. Abrasive wear properties of LDPE and its composites were determined under multi‐pass mode; pure LDPE showed minimum specific wear rate. The specific wear rate of composites decreased with the sliding distance. Increase of coated sisal fiber content increased the specific wear rate at all the sliding distances, which has been explained on the basis of worn surface microstructures observed by using SEM. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

An impact of bias and structure dependent L_\mathrm{SD} variation on the performance of GaN HEMTs based biosensor

In this paper, we discussed the effect of different bias and structures in relation to S-D distance variation on the device electrical and expected biosensing performance. Devices with source to drain length ( \(L_{SD})\) variations from 3.5, 5.0, 8.0, 14.0, 26.0 to \(52~\upmu \) m were simulated at low and high bias voltages. Different structures having gate recess and finger variations were investigated for the complete range of \(L_{SD}\) variations. Small and very large \(L_{SD}\) variations in non-recessed structure showed good values of drain current \((I_{ds})\) and transconductances \((g_{m})\) at different low and high bias voltages respectively. Therefore expected response time and sensitivity could be improved by choosing a proper bias condition for different biosensing \(L_{SD}\) lengths. A gate recess structure showed better \(g_{m}\) values at low bias conditions for all \(L_{SD}\) lengths. However, \(I_{ds}\) degraded for these structures and hence the expected response time. The non-recessed structure variations in terms of number of fingers and gate width did not change the effective trends in \(L_{SD}\) variation.     

Mechanical and thermal properties of polypropylene nanocomposites using organically modified Indian bentonite

We report preparation and characterization of nanoclay from Indian bentonite and imported nanoclays, and their compounding with polypropylene (PP) and maleic anhydride‐grafted PP (MA‐g‐PP) in twin screw extruder. The compounded polymer/nanoclay nanocomposites (PNCs) are molded into a standard specimen for studying its tensile, flexural and impact strength. A wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM) study demonstrates intercalation of PP in nanoclays rather than exfoliation for both, indigenous and imported nanoclays. The tensile modulus increased by 41 and 39% for PNC1 (PNC with imported nanoclay) and PNC2 (PNC with indigenous nanoclay) with respect to PP. The flexural modulus for PNC1 and PNC2 also increases by 23 and 22% due to incorporation of 5% nanoclay in PP along with 5% MA‐g‐PP. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Direct Internal Reformation and Mass Transport in the Solid Oxide Fuel Cell Anode: A Pore‐scale Lattice Boltzmann Study with Detailed Reaction Kinetics

The solid oxide fuel cell (SOFC) allows the conversion of chemical energy that is stored in a given fuel, including light hydrocarbons, to electrical power. Hydrocarbon fuels, such as methane, are logistically favourable and provide high energy densities. However, the use of these fuels often results in a decreased efficiency and life. An improved understanding of the reactive flow in the SOFC anode can help address these issues. In this study, the transport and heterogeneous internal reformation of a methane based fuel is addressed. The effect of the SOFC anode's complex structure on transport and reactions is shown to exhibit a complicated interplay between the local molar concentrations and the anode structure. Strong coupling between the phenomenological microstructures and local reformation reaction rates are recognised in this study, suggesting the extension to actual microstructures may provide new insights into the reformation processes.     

Primary measurement of total ultrasonic power with improved accuracy in rf voltage measurement

Out of the various existing ultrasonic power measurement techniques, the radiation force balance method using microbalance is most widely used in low power (below 1 W) regime. The major source of uncertainty associated with this technique is the error in ac voltage measurement applied to the transducer for the generation of ultrasonic waves. The sources that deteriorate the ac voltage measurement accuracy include cable length and impedance mismatch. We introduce a new differential peak to peak measurement approach to reduce the ac voltage measurement error. The method holds the average peak amplitude of each polarity. Ultralow offset difference amplifier is used to measure peak to peak voltage. The method is insensitive to the variations in the dc offset of the source. The functionality of this method has been tested and compared with the conventional rf voltage measurement method. The output of this proposed technique is dc, which can be measured with an error of less than 0.1%.     

Effect of treatment of Bis(3‐triethoxysilyl propyl)tetrasulfane on physical property of in situ sodium activated and organomodified bentonite clay – SBR rubber nanocomposite

This study describes the effect of treatment of Bis(3‐triethoxysilyl propyl)tetrasulfane (silane coupling agent, Si69, TESPT) on in situ sodium activated, organo modified bentonite clay – styrene butadiene rubber (SBR) nanocomposite. transmission electron microscopy and Wide angle X‐ray diffraction indicated the intercalation as well as partial exfoliation in both the organoclay and silane treated organoclay compound. It was found that about 5% of silane with respect to clay was the optimum dose for the treatment. Around 15% improvement in tensile and tear strength was observed due to silane treatment. Silane treated organoclay exhibited substantial improvement of the fatigue life, compression set, and rebound property. A detailed study of physical property was carried out. A comparison with low and high structure carbon black filled compound was also carried out. It revealed that the silane treatment helped organoclay to achieve comparable property of the compound having equivalent carbon black loading. Probable mechanism of interaction of silane with clay has also been proposed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of highly filled wood flour–polyvinyl chloride composites: Dynamic mechanical and dielectric analysis

Viscoelastic and dielectric properties of composites with polyvinyl chloride as major matrix constituent, ethylene vinyl acetate (EVA) as polymeric plasticizer, and wood flour (WF) and fly ash (FA) as filler have been studied. The effect of variation of WF, FA, and EVA on storage modulus E′, loss modulus E″, and glass transition temperature, T_g has been evaluated using dynamic mechanical analysis (DMA). Effect on permittivity ε′ and conductivity is evaluated using dielectric analysis. The results show considerable influence of constituents of the composite on the properties evaluated. DMA shows that WF contributes to an increase in T_g, E′, and E″ and a decrease in loss tangent, tan δ. The FA content has insignificant effect on these properties. Increasing WF content increases ε′. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers