Output regulation for non‐square linear multi‐rate systems

We address the problem of regulating a subset of outputs of a linear time‐invariant plant with multi‐rate measurements so as to achieve asymptotic tracking of an exogenous signal generated by the free motion of a linear time‐invariant system, denoted by exosystem. A solution to this problem is required to yield closed‐loop stability and should be such that output regulation is achieved even in the presence of small plant uncertainties and exogenous disturbances also generated by the exosystem. Contrarily to previous works, we propose a solution to the general case where the plant may have more measured outputs than inputs. We show that this solution allows us to solve simultaneous stabilization and output regulation problems that are not possible to solve through the previous works. Besides incorporating an internal model of the exosystem, the key feature of our proposed controller is that it includes a system that blocks signals generated by the exosystem arriving to the controller from the non‐regulated outputs. Copyright © 2012 John Wiley & Sons, Ltd.     

CPMD-mindful task assignment for NPS-F

The multiprocessor scheduling scheme NPS-F for sporadic tasks has a high utilisation bound and an overall number of preemptions bounded at design time. NPS-F binpacks tasks offline to as many servers as needed. At runtime, the scheduler ensures that each server is mapped to at most one of the m processors, at any instant. When scheduled, servers use EDF to select which of their tasks to run. Yet, unlike the overall number of preemptions, the migrations per se are not tightly bounded. Moreover, we cannot know a priori which task a server will be currently executing at the instant when it migrates. This uncertainty complicates the estimation of cache-related preemption and migration costs (CPMD), potentially resulting in their overestimation. Therefore, to simplify the CPMD estimation, we propose an amended bin-packing scheme for NPS-F allowing us (i) to identify at design time, which task migrates at which instant and (ii) bound a priori the number of migrating tasks, while preserving the utilisation bound of NPS-F.     

Effect of active site distribution on liquid-phase olefin hydrogenation over polymer-supported palladium complex

Chloromethylated polystyrene beads with different distributions have been prepared and phosphinated. PdCl₂ was supported on the phosphinated supports to give polymer-supported Pd complex catalysts with different active site distributions. The effect of active site distribution on catalytic activity was investigated in the hydrogenation of olefins.     

A TPD study of H2 ON Ru/SiO2 and Ru-Cu/SiO2

In H₂ TPD from Ru/SiO₂, two desorption peaks were observed. Both exchanged H for D in sequential dosing experiments. These hydrogen adsorption states were also found for Ru-Cu/SiO₂, along with another, higher temperature state at 400–500 K. This last state was neither exchangeable with nor replaceable by deuterium subsequently dosed at 150 K. The three chemisorption states are attributed to hydrogen held at the interface between Ru and SiO₂ (< 300 K), adsorbed on Ru particles (310–380 K), and held at the Ru-Cu interface (> 400 K).     

Constitutive modeling for intercalated PMMA/clay nanocomposite foams

A constitutive model for tensile behavior of PMMA/clay nanocomposite foams was developed in this study. The elastic modulus of the nanocomposites is affected by the form of clays embedded in the polymer matrix. The reinforcing effect by intercalation of the clays and the detrimental effect by clay agglomeration were considered for the determination of the elastic modulus of the nanocomposites. A viscoelastic model was adapted for the tensile behavior of the material. The developed constitutive equation is expressed in terms of clay morphology and material properties. The aspect ratio of clays and the expansion of clay layer spacing in the intercalated clay clusters were proved to play a vital role in the reinforcing mechanism. For the verification of the constitutive model, Poly(methyl‐methacrylate) (PMMA)/clay nanocomposite foams were manufactured by batch process method and their uniaxial tensile test results were compared with theoretical predictions. Compared with the experimental results, the proposed constitutive equation showed agreement with the experimental test results. POLYM. ENG. SCI. 46:1787–1796, 2006. © 2006 Society of Plastics Engineers.     

Effect of solvent or hydrophilic polymer on the hydration melting behavior of polyacrylonitrile

The effect of solvent, DMF, and hydrophilic polymer on the hydration melting behavior of Tae Kwang polyacrylonitrile-based copolymer (T-PAN) was investigated by DSC measurement. The melting temperature (T_m) of T-PAN was sharply lowered by incorporating water under autogenous pressure, but leveled off above a critical water content: 23 wt %. However, an additional incorporation of DMF into the hydrated T-PAN further lowered the T_m, even above the critical water content. On the other hand, addition of water-soluble poly(acrylic acid), poly(vinyl alcohol), and poly(ethylene glycol) or water-swellable starch to the hydrated PAN slightly raised the T_m. © 1994 John Wiley & Sons, Inc.     

Comparison of vertical and horizontal slot die coatings

Comparison of vertical and horizontal slot coatings was carried out experimentally using aqueous glycerin solutions with varying viscosity on a laboratory‐scale slot coater. The maximum coating speeds achieved in vertical slot coating were found to be higher than those of horizontal slot coating for low‐viscosity solutions. The coating defects observed below the minimum wet thickness changed from ribbing to air entrainment at a critical solution viscosity of around μ = 75 mPa s. Above this critical viscosity, a lower minimum wet thickness was obtained for the horizontal coating but not for vertical coating. The difference between vertical and horizontal coating was mainly the length of the coating bead. The dimensionless minimum wet thickness was correlated as a function of Reynolds number. There existed three regions of minimum wet thickness depending on Reynolds number. Initially, the dimensionless wet thickness increased in the low Reynolds number region (Region I), then reached a plateau in the intermediate Re region (Region II), finally dropped off sharply in the high Re region (Region III). The boundaries of these three regions were identified by two critical Reynolds numbers, i.e., Re = 1 and 20. Only Regions I and II of the wet thickness could be found for horizontal coating, while mainly Regions II and III were obtained for vertical coating, depending on the viscosity of the coating solution. POLYM. ENG. SCI., 47:1927–1936, 2007. © 2007 Society of Plastics Engineers     

Transesterifications in a polyblend of poly(butylene terephthalate) and a liquid crystalline polyester

Transesterfication between a liquid crystalline polyster and poly(butylene terephthalate) was followed quantitatively by analyzing ¹³C-NMR spectra of the 50:50 blend after heat treatmetn at 290°C for varying lengths of time. Differential scanning nalysis was employed to follow the interchange reactions. From analysis of triad sequences of the transesterified blends, it was clear that measurable exchange reactions occurred when the blend was kept at 290°C for 20 min. The distribution of sequences tends to approach that of a statistical binary copolymer as the heat treatment period is increased. The results ontained from this investigation show that polyblends between an LC polyesterand conventional polyesters must be handled carefully. Otherwise, ester interchange reactions are inevitable.     

Synthesis of organic–inorganic hybrid polymeric nanocomposites for the hard coat application

An organic–inorganic hybrid polymeric nanocomposite has been synthesized for making UV‐curable hard coats. This nanocomposite consists of nano‐sized colloidal silica functionalized with vinyltriethoxysilane (VTES) and dendritic acrylic oligomers (DAO) which have been formed earlier via a reaction of ethylenediamine (EDA) with trimethylopropane triacrylate (TMPTA). Applied as a hard coat on top of a polyethylene terephthalate (PET) film, this nanocomposite has a short UV‐cure time and the cured coat has an enhanced thermal decomposition temperature (T_d), 89–90% transparency, increased hardness up to 3H, better adhesion up to 4B, and a flat surface with a root mean square roughness of 2–4 nm. The preparation as well as the characterization of the constituting species and the final hybrid are described in detail. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3985–3993, 2007     

A Weighted Delaunay Triangulation Framework for Merging Triangulations in a Connectivity Oblivious Fashion

Simplicial meshes are useful as discrete approximations of continuous spaces in numerical simulations. In some applications, however, meshes need to be modified over time. Mesh update operations are often expensive and brittle, making the simulations unstable. In this paper we propose a framework for updating simplicial meshes that undergo geometric and topological changes. Instead of explicitly maintaining connectivity information, we keep a collection of weights associated with mesh vertices, using a Weighted Delaunay Triangulation (WDT). These weights implicitly define mesh connectivity and allow direct merging of triangulations. We propose two formulations for computing the weights, and two techniques for merging triangulations, and finally illustrate our results with examples in two and three dimensions.