Preparation and properties of (BATB–ODPA) polyimide–clay nanocomposite materials

A series of polymer–clay nanocomposite (PCN) materials consisting of 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene–4,4′‐oxydiphthalic anhydride (BATB–ODPA) polyimide (PI) and layered montmorillonite (MMT) clay were successfully prepared by an in situ polymerization reaction through thermal imidization up to 300°C. The synthesized PCN materials were subsequently characterized by Fourier‐Transform infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of material composition on thermal stability, mechanical strength, molecular permeability and optical clarity of bulk PI and PCN materials in the form of membranes were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), molecular permeability analysis (GPA) and ultraviolet‐visible (UV/VIS) transmission spectra, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1072–1079, 2004     

A group decision classifier with particle swarm optimization and decision tree for analyzing achievements in mathematics and science

Group decision making is a multi-criteria decision-making method applied in many fields. However, the use of group decision-making techniques in multi-class classification problems and rule generation is not explored widely. This investigation developed a group decision classifier with particle swarm optimization (PSO) and decision tree (GDCPSODT) for analyzing students’ mathematic and scientific achievements, which is a multi-class classification problem involving rule generation. The PSO technique is employed to determine weights of condition attributes; the decision tree is used to generate rules. To demonstrate the performance of the developed GDCPSODT model, other classifiers such as the Bayesian classifier, the k-nearest neighbor (KNN) classifier, the back propagation neural networks classifier with particle swarm optimization (BPNNPSO) and the radial basis function neural networks classifier with PSO (RBFNNPSO) are used to cope with the same data. Experimental results indicated the testing accuracy of GDCPSODT is higher than the other four classifiers. Furthermore, rules and some improvement directions of academic achievements are provided by the GDCPSODT model. Therefore, the GDCPSODT model is a feasible and promising alternative for analyzing student-related mathematic and scientific achievement data.     

Solar Photocatalytic Degradation of Textile Dyes in TiO2 Suspended Solutions

The degradation and decolourization of direct dye (Everdirect supra turguoise blue, FBL), acidic dye (Isolan orange S-RL) and vat dye (Indanthren red FBB) have been investigated by solar/TiO2 process. The effects of solution pH, dye concentration, dosage of TiO2 and nano-size of TiO2 have been studied. The increase in initial pH (3, 5 and 11) and dye concentration decrease the removal rate. The treatment for FBB and FBL dye solutions is more efficient than that of S-RL.Under optimum conditions, the color removal is found to be almost complete for FBB and FBL while that of S-RL also reaches 95%. Langmuir adsorption isotherm and modified Langmuir-Hinshelwood kinetic model (L-H model) have been fitted to the experimental data and found to correlate the adsorption patterns as well as the kinetics of the dyes studied.     

Determination of the elastic component for polymeric melt under steady shear flow

Steady state shear flow in rectilinear coordinates can be generated by a direct shear rheometer. The rheological behavior of polymeric melts under shear flow can be characterized by the inception of steady shear flow and stress relaxation after cessation of steady shear flow. Experiments were performed for bisphenol A polycarbonate with various mol wts. The elastic components, such as the primary normal stress differences and the elastic recoverable shear strain of the polymeric melts, can be determined from the shear moduli. © 1993 John Wiley & Sons, Inc.     

ADHESION OF ELASTOMERS: DWELL TIME EFFECTS

The strength of adhesion of elastomers to rigid substrates generally increases with time of contact. This effect has been studied for samples of butyl and chlorobutyl rubber adhering to some rigid substrates. The peel strength increased continuously over long periods of contact until in some cases failure became cohesive within the elastomer layer. At higher temperatures the strength increased more rapidly, consistent with the WLF relation governing molecular motions. It is postulated that slow molecular rearrangements occur at the interface and increase the bond strength. A criterion for the observed transition from interfacial to cohesive failure is suggested.     

Manufacturing and foaming of high melt viscosity of polypropylene by using electron beam radiation technology

The high melt viscosity of polypropylene was studied by grafting bifunctional monomers, 1,6‐hexanediol diacrylate (HDDA) and tripropylene glycol diacrylate (TPGDA), onto homopolypropylene (HPP) and random ter‐polypropylene (RTPP) under electron‐beam irradiation. Creation of the high‐melt‐viscosity polypropylene was possible at low radiation dosage and low monomer content, under a prohibition of both radiation degradation and homopolymerization. TPGDA monomer was more effective in increasing the melt viscosity of HPP compared with RTPP, whereas HDDA monomer was more effective for enhancing the melt viscosity of RTPP. Such different effects of monomers on melt viscosity may arise from different monomer structures, namely, TPGDA has additional three methyl groups, but HDDA has no methyl groups. Electron‐beam radiation technology, on an increase of the melt viscosity, was much more effective in HPP than RTPP, when compared with virgin polymers. Modified RTPP and HPP with high melt viscosity were capable of foaming with numerous fine cells, of which the modified HPP with 1.5 mmol TPGDA and 0.5 kGy could create more spherical foam cells and its bending strength was 1.5 times more than that of the foamed RTPP. POLYM. ENG. SCI., 46:431–437, 2006. © 2006 Society of Plastics Engineers.     

Design and control of reactive distillation for ethyl and isopropyl acetates production with azeotropic feeds

Reactive distillations for the production of ethyl acetate (EtAc) and isopropyl acetate (IPAc) are classified as the type-II process where the first column consists of a reactive zone and a rectifying section followed by a stripper [Tang et al., 2005. Design of reactive distillations for acetic acid esterification with different alcohols. A.I.Ch.E. Journal 51, 1683-1699]. Instead of using pure alcohols and acetic acid as reactants, this paper studies the effects of reactant purity on the design and control of reactive distillation. This offers significant economical incentives (by reducing raw materials costs), because ethanol forms an azeotrope with water at 90 mol% and isopropanol/water has an azeotrope at 68%. The purities of the acid is set to 95% for acetic acid (industrial grade), 87% for ethanol, and 65% for isopropanol. The results show that the total annual costs (TAC) increase by a factor of 5% for EtAc and 8% for IPAc production using reactive distillation. Next, the operability of the reactive distillations with azeotrope feeds is explored. Three disturbances, feed flow, acid feed purity, and alcohol feed composition, are introduced to assess control performance using dual-temperature control and one-temperature-one-composition control. Simulation results indicate good control performance can be achieved for reactive distillation with azeotropic feeds.     

Synthesis and characterization of novel copolymers with acid‐labile ketal moieties derived from camphor

Novel diastereomeric acrylic ketal monomers derived from (+)‐camphor and (±)‐camphor were synthesized. To investigate the applications of the camphor derivatives on positive‐tone photoresists, the acrylic ketal monomers were copolymerized with methyl methacrylate, methacrylic acid, and n‐butyl methacrylate. The optical activities of the chiral monomers and polymers were all evaluated. After UV irradiation and postexposure baking, the optical activity of the polymers decreased because of the decomposition of the acid‐labile pendant chiral groups. The existence of alicyclic camphyl groups increased the etching resistance of the photoresists. The thermogravimetric properties of the copolymers, the exposure curves, the lithographic evaluation of the positive‐tone photoresists, and the effects of alicyclic groups on the plasma etching resistance of the copolymers were all investigated. A resolution of a line‐and‐space pattern of 0.3 μm was achieved. Acid‐catalyzed dehydration crosslinking was also found in this system. Sufficient UV irradiation and heat treatment could cause the acid‐catalyzed dehydration crosslinking of pendant carboxyl groups and thereby increase the efficiency of the thermal resistance of the polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2969–2978, 2003     

Sliding-mode and proportional-derivative-type motion control with radial basis function neural network based estimators for wheeled vehicles

An obstacle avoidance problem of rear-steered wheeled vehicles in consideration of the presence of uncertainties is addressed. Modelling errors and additional uncertainties are taken into consideration. Controller designs for driving and steering motors are designed. A proportional-derivative-type driving motor controller and a sliding-mode steering controller combined with radial basis function neural network (RBFNN) based estimators are proposed. The convergence properties of the RBFNN-based estimators are proven by the Stone–Weierstrass theorem. The stability of the proposed control law is proven using Lyapunov stability analysis. The obstacle avoidance strategy utilising the sliding surface adjustment to an existing navigation method is presented. It is concluded that the driving velocity and steering-angle performances of the proposed control system are satisfactory.     

Analysis of cell aggregation in the culturing of cerebellar granule neurons

We have proposed previously that an increased concentration of growth factor secreted by neurons themselves has a direct effect on survival of the neurons, and thereby cell density serves as a regulator of survival of neurons. In this study, the same idea was used to analyze the aggregation of cerebellar granule neurons in culture experimentally and theoretically. Assuming the transport of growth factor and substrate within an aggregate is by molecular diffusion, the metabolic efficiency of neurons, on the basis of an autocatalytic phenomenon, was increased within an aggregate compared to an identical quantity of dispersed cells. A good agreement in the size of neuronal aggregate between the theoretical prediction and the experimental result was found. This illustrates that growth factors produced by neurons acting in either an autocrine or paracrine manner play an important role during the development of cultured neurons.