Specially orthotropic panel flutter control using PID controller

Controlling the flutter speed of a specially orthotropic plate of rectangular cross-section through which an inviscid compressible fluid flows is considered. A state-space model of the coupled aeroelastic system helps us to determine flutter boundaries and provides a method for applying modern control theory to the problem. So in the present study, flow is modelled by piston theory and the coupled state-space model of panel motion and flow is solved. After that, the coupled system is controlled with Proportional-Integral-Derivative controller. This makes it possible to compute the flutter dynamic pressure and so the flutter velocity at which unstable plate oscillations occur as a function of the gain coefficient. It is found that by changing the gain coefficient the flutter of the plate can indeed be pushed to higher velocities.     

Physicochemical Characterization of Whole Egg Powder Microencapsulated by Spray Drying

Physical characterization and oxidative stability of egg powder microencapsulated by spray drying were studied in this work. The wall material (gelatin, lactose, pullulan, and their mixtures) and liquid egg mixtures were prepared by homogenization at 22,000 rpm for 60 s. The spray drying was carried out at pilot-scale spray dryer (Niro Mobile Minor, Søborg, Denmark). The spray-dried egg powders were analyzed for moisture content, water activity, peroxide value, total cholesterol oxidation products (TCOPs), particle properties, and bulk properties. Using gelatin as wall material resulted in a significant increase in the moisture content and water activity of egg powder during storage and it improved flowability. Egg powders containing pullulan as wall material showed a fibrous structure and had the lowest bulk density. Adding lactose as wall material increased the oxidative stability, which was indicated with lowest peroxide value and TCOPs level of egg powder.     

A novel benzoxazine monomer with methacrylate functionality and its thermally curable (co)polymers

Benzoxazine monomer with methacrylate functionality, namely 2-(2-(2H-benzo[e][1,3]oxazin-3(4H)-yl)ethoxy) ethyl methacrylate (BEM) was synthesized by simple esterification reaction of hydroxyl containing benzoxazine (B–OH) with methacryloyl chloride, and characterized. BEM was then copolymerized with styrene in 1:4 mol ratio by free radical polymerization using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. The structure, chemical composition, and molecular weight characteristics of the resulting copolymer were confirmed by FT-IR, ¹H-NMR spectroscopy, and GPC, respectively. The curing behavior and thermal properties of both monomer and copolymer were also studied by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).     

Acrylic terpolymer modified by blending with polyorganosiloxane polymer or reinforcing

Blending of acrylic terpolymer (AT) and polyorganosiloxane (PSP) resulted in homogeneous blends with improved mechanical properties and better outdoor weathering resistance. Similarly, incorporation of glass fibres in concentrations of 1–3% produced substantially better mechanical properties and enhanced outdoor durability in the resulting blends.     

Removal of 17beta-estradiol (E2) and its chlorination by-products from water and wastewater using non-imprinted polymer (NIP) particles

Endocrine disrupting compounds and their chlorination by-products are two classes of emerging contaminants. Surface water and wastewater treatment technologies have limitations in removing these contaminants. This study evaluated the ability of non-imprinted polymer particles (NIP) to remove the endocrine disruptor 17beta-estradiol (E2) and its chlorination by-products from water and wastewater. NIP effectively removed 98% of 10 mg/L E2 from wastewater. NIP were also effective in removing chlorination by-products of E2 by 84.9% after 10 mg/L E2 in water was chlorinated at 5 mg/L. In the presence of 5 mg/L humic acid, NIP were able to achieve removal of 10 mg/L E2 by greater than 99.9%. Furthermore, after chlorination of 10 mg/L E2 and 5 mg/L humic acid at 10 mg/L chlorine, NIP were also able to remove the chlorination by-products formed as well as the remaining E2 by greater than 99.9%. The presence of 5 mg/L humic acid did not adversely affect the adsorption efficiency. The results of this research indicate that NIPs have good potential as a final treatment step for surface water and wastewater treatment.     

Robust flow control in data‐communication networks with multiple time‐delays

Robust controller design for a flow control problem where uncertain multiple time‐varying time‐delays exist is considered. Although primarily data‐communication networks are considered, the presented approach can also be applied to other flow control problems and can even be extended to other control problems where uncertain multiple time‐varying time‐delays exist. Besides robustness, tracking and fairness requirements are also considered. To solve this problem, an ??^∞ optimization problem is set up and solved. Unlike previous approaches, where only a suboptimal solution could be found, the present approach allows to design an optimal controller. Simulation studies are carried out in order to illustrate the time‐domain performance of the designed controllers. The obtained results are also compared to the results of a suboptimal controller obtained by an earlier approach. Copyright © 2009 John Wiley & Sons, Ltd.     

Unfolding events of Chymotrypsin Inhibitor 2 (CI2) revealed by Monte Carlo (MC) simulations and their consistency from structure-based analysis of conformations

We investigated the behavior of the conformations of Chymotrypsin Inhibitor (CI2) from the native to the denatured states, obtained in Monte Carlo (MC)/Metropolis simulations, where a low-resolution model is used together with knowledge-based potentials. New conformations starting from the X-ray native structure are generated by random perturbations along with a constraint to increase the radius of gyration. Unfolding is also simulated by unrestrained simulations at a higher temperature. All simulations yield a similar sequence of unfolding events. The preferred pathway starts with loss of native contacts between (N-terminal)-β₃ and continues with β₂-β₃. The persistence of the contacts between β₁ and β₂ at intermediate values of the fraction of native contacts (Q); whereas, highly unfolded conformations with only some helical contacts persisting at low values of Q, are observed. Structure-based analysis of the fluctuations of the unfolded conformations by Gaussian Network Model (GNM) reveals that the termini of the chain—C terminus being more mobile—depict relatively higher flexibility with a native-like hinge near β₂ that divides the structure into two domains. The fluctuations of the two domains are negatively correlated, with partly folded α-helix and a small hydrophobic cluster in the middle of the chain displaying positively correlated fluctuations. The most persistent short-range rotational bond correlations are observed between the residues of α-helix, C terminus of the β₁-part of the reactive site loop, and around the C terminus of the β₂. The latter regions also appear as hot spots; i.e. high frequency fluctuating regions, of the structure surviving in unfolded conformations. The results imply that the unfolded CI2 has an intrinsic ability to undergo correlated fluctuations along with some residual native structure specifically induced by its sequence, consisting at the lowest level of a single hinge.     

Determining the dependence of colour values on yarn structure

The colour values of knitted cotton fabrics made from single and plied ring and compact yarns were investigated before and after dyeing. The fabric samples were knitted under the same constructional properties and then dyed with direct and reactive dyes. It was found that fabrics with ring yarns had high lightness and low chroma and colour strength values compared with fabrics with compact yarns. Also colour strength and colour difference values of dyed fabrics were assessed after increasing abrasion cycles (2500, 5000, 7500 and 10 000). The main changes in colour strength values were observed at 2500 abrasion cycles. The effect of abrasion on colour difference values of fabrics having ring yarns was more obvious than fabrics having compact yarns.     

Epoxy–lignin polyblends: Correlation between polymer interaction and curing temperature

A bisphenol A–polyamine hardener based epoxy adhesive (EP) was modified by polyblending with Kraft lignin (L). EP–L polyblends with an L content up to 40% by weight were cured at room temperature or above their glass transition temperature (T_g). Previous data have shown that the thermal and viscoelastic properties, as well as adhesive performance of the EP–L polyblends, are influenced by the curing temperature and by the L content in thermally cured polyblends. A reasonable explanation for the different behavior of EP–L polyblends as function of the curing temperature and their L content could be the enhanced degree of bonding between L and the EP network taking place at elevated temperature. This bonding was specifically considered to take place between L and possible unreacted amine groups of the hardener. Characterization of the EP–L polyblends was performed to search for evidence of irreversible chemical bonding between L and the EP network in thermally cured EP–L polyblends. FTIR studies, L extractibility from the crosslinked, polyblends, and quantitative data concerning the reactivity of L toward the polyamine hardener are discussed.