Kinetic study of olefin polymerization with a supported metallocene catalyst. II. Ethylene/1‐hexene copolymerization in gas phase

A kinetic study of ethylene/1‐hexene copolymerization is conducted with a supported metallocene catalyst in a gas‐phase reactor. The investigation into the kinetics of ethylene/1‐hexene copolymerization includes the effects of operational parameters such as the reaction temperature, pressure, and comonomer concentration. The large variations in gas‐phase composition using only an initial charge of 1‐hexene are illustrated by experiment. To remedy this, the ability to control the comonomer composition of 1‐hexene online for the entire duration of the reaction is demonstrated. Online perturbation techniques are implemented to determine key kinetic parameters such as the activation energies for propagation and catalyst deactivation. From pressure perturbation results, a reaction rate order close to 1 is obtained for ethylene in the presence of 1‐hexene. Finally, all the parameters obtained from the study are compared to those determined from ethylene–propylene (E–P) copolymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1096–1119, 2001     

Kinetic study of olefin polymerization with a supported metallocene catalyst. III. Ethylene homopolymerization in slurry

A kinetic study of ethylene homopolymerization is conducted with a supported unbridged metallocene catalyst in a slurry reactor. The effects of operational parameters such as the reaction temperature and pressure on kinetics are investigated. The kinetic parameters which have been determined for this particular catalyst from previous gas phase studies are used in a slurry reactor model to predict the polymerization behavior under various reaction conditions. The experimental data compare favorably with the predictions from this model. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2901–2917, 2001     

Removal of pentane and styrene mixtures from waste gases by a trickle‐bed air biofilter

The biofilter process is a relatively new technology that has been proven to be more cost‐effective than traditional technologies for treating many kinds of volatile organic compounds (VOCs) from waste gases. Pentane and styrene mixtures are commonly encountered in the manufacture of polymers such as polystyrene. This research attempts to employ a trickle‐bed air biofilter (TBAB) for treating such mixtures under different influent carbon loadings. In the pseudo‐steady‐state conditions, the elimination capacities of pentane and styrene increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of styrene were higher than those of pentane, indicating that styrene is a preferred substrate and the differences were enhanced at a high carbon loading. Removal efficiencies of more than 80% were achieved with influent carbon loadings of pentane and styrene below 25 and 68 gm^?3 h^?1, respectively. The TBAB appears to be efficient for controlling VOC emissions with low pentane and medium styrene loadings, and the effectiveness could be maintained over 140 days of laboratory operation. © 2001 Society of Chemical Industry     

Asymmetric twin-waveguide 1.55-μm wavelength laser with adistributed Bragg reflector

We demonstrate a single frequency, 1.55 μm wavelength laser based on an asymmetric twin-waveguide structure using a single growth step and a simple fabrication process. The external Bragg grating is formed on the passive ridge waveguide, optically coupled to the twin-guide gain section using a low loss, tapered mode transformer. The grating is produced by near-field holographic printing using a phase mask. Output powers >11 mW in a small-spot waveguide with a side-mode suppression ratio >40 dB and a slope efficiency of 0.11 W/A are obtained under pulsed operation. These performance characteristics are comparable to conventional, nonintegrated, conventional discrete DBR lasers, although the twin-waveguide design is compatible with photonic integrated circuits such as monolithic transmitters and WDM coherent receivers     

An inner product space on irreducible and synchronizable probabilistic finite state automata

Probabilistic finite state automata (PFSA) have found their applications in diverse systems. This paper presents the construction of an inner-product space structure on a class of PFSA over the real field via an algebraic approach. The vector space is constructed in a stationary setting, which eliminates the need for an initial state in the specification of PFSA. This algebraic model formulation avoids any reference to the related notion of probability measures induced by a PFSA. A formal language-theoretic and symbolic modeling approach is adopted. Specifically, semantic models are constructed in the symbolic domain in an algebraic setting. Applicability of the theoretical formulation has been demonstrated on experimental data for robot motion recognition in a laboratory environment.     

Determining Kinetic Parameters for Isothermal Crystallization of Glasses

Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. The techniques are experimentally simple and quick, compared with isothermal techniques. However, the analytical models used for non-isothermal data analysis, that were derived from models originally developed for describing isothermal transformation kinetics, are fundamentally flawed. The present paper describes a technique for determining the kinetic parameters for isothermal crystallization in glasses, which eliminates most of the common problems that generally make the study of isothermal crystallization laborious and time consuming. In this technique, the volume fraction of a glass that is crystallized as a function of time during an isothermal hold was determined in a separate experiment using differential thermal analysis. The activation energy (345±10 kJ/mole) and Avrami parameter (0.89±0.09) for crystallization of Li₂O·2SiO₂ glass determined by the present technique are consistent with the similar values reported in the literature.     

Increase in open circuit voltage by the incorporation of band gap engineered FeS2 nanoparticle within MEHPPV solar cell

In this study we have synthesized and characterized FeS₂ nanoparticles with larger optical band gap (3.19 eV) and high thermal stability by hydrothermal route with capping reagent PEG 400. This high quality FeS₂ nanoparticle with higher band gap energy was applied as semiconducting acceptor in MEHPPV:FeS₂ nanoparticle based hybrid solar cells to improve the open circuit voltage. Variations in the property of FeS₂ have been done and confirmed by XRD, FE-SEM, TEM, FTIR, TGA, UV–VIS spectroscopy and Raman study. Two types of solar cells have been fabricated with structures: ITO/PEDOT:PSS/MEHPPV/Al and ITO/PEDOT:PSS/MEHPPV:FeS₂/Al. The open circuit voltage has been increased from 0.64 to 0.72 V by compositing FeS₂ nanoparticle within MEHPPV matrix.     

Linearly polarized emission from PTCDI-C8 one-dimensional microstructures

Linearly polarized emission has been observed from a crystalline one-dimensional (1D) microstructure fabricated from N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈) molecules via solution phase self-assembly. Rotating microscopy imaging of a 1D microstructure under crossed polarization was performed for the investigation of polarized emission. The anisotropy birefringence was maximum only when the 1D microstructure was aligned 45° to the direction of the polarizer and it was minimum when aligned parallel to the polarizer implying that the transmission axis of the 1D microstructure is perpendicular to its π–π stacking direction. A model has been proposed to explain linearly polarized emission from the microstructure.