Solid-state polymerization vis-à-vis fiber formation of step-growth polymers. I. Results from a study of nylon 66

This study is directed toward synergistic integration of processing of nylon 66 fibers with solid-state polymerization. The following two goals are sought through the incorporation of solid-state polymerization after the initial shaping operation: eliminating some of the processing problems in the production of high molecular weight, high performance industrial fibers and attainment of improved mechanical properties via high molecular weight. Successful solid-state polymerization has been achieved with as-spun fibers of nylon 66 and molecular weights up to 280,000 g/mol have been obtained from a starting molecular weight of 40,000 g/mol. It is shown that much of the ductility of the starting fiber can be retained, or even enhanced, with solid-state polymerization. Simulated drawing experiments using a thermal deformation analysis technique show an increase in the drawing potential of the solid-state polymerized fiber as compared to the starting material. This has important implications regarding the ultimate properties that can be achieved in fibers of condensation polymers. © 1994 John Wiley & Sons, Inc.     

MULTIPLE REGRESSION AND COMMITTEE NEURAL NETWORK FORCE PREDICTION MODELS IN MILLING FRP

This work utilizes the mechanistic modeling approach for predicting cutting forces and simulating the milling process of fiber-reinforced polymers (FRP) with a straight cutting edge. Specific energy functions were developed by multiple regression analysis (MR) and committee neural network approximation (CN) of milling force data and a cutting model was developed based on these energies and the cutting geometry. It is shown that both MR and CN models are capable of predicting the cutting forces in milling of unidirectional and multidirectional composites. Model predictions were compared with experimental data and were found to be in good agreement over the entire range of fiber orientations from 0 to 180°. Furthermore, CN model predictions were found to greatly outperform MR model predictions.     

A framework for rapid computational prototyping of manufacturing entities

A framework for enhancement of conceptual tools for rapid computational prototyping of manufacturing entities is presented. A typical manufacturing entity (i.e. manufacturing system and/or individual part) is hierarchically represented in a computer and coupled with applications by dividing its information content into three computational elements: data, drawing and user interface. The information content is divided in this way because each of the above elements has a sufficiently distinct requirement for an efficient computer implementation. Although independent advances have taken place in computer data representation by highly efficient and focused data structures, in drawing representation by sophisticated computer graphics, as well as in user interface by a variety of interface media, these advances cannot be directly utilized in the design of a manufacturing entity unless they are efficiently integrated by relatively small programming effort as is deseribed in this rapid prototyping framework. The framework is implemented in object-oriented programming. A breadth of application areas for the framework is illustrated, and specific details are illustrated with reference to depth in one application area.     

Eu（Ⅲ） Indirect Probe to Investigate Interaction of DOPA （3, 4, Di-Hydroxyphenylalanine） and Dopamine （3, 4-Dihydroxy Phenyl Ethyl Amine） Using Electrochemical Methods

Eu（ Ⅲ ） can be utilized as an indirect electrochemical probe to investigate the interaction of bio-molecules such as DOPA and Dopamine with Ca（ Ⅱ ） in vitro. The interaction of DOPA and Dopamine with Eu（ Ⅲ ）-Eu（ Ⅱ ） redox pair was investigated by electrochemical techniques. Both the neurotransmitters are structurally related and undergo interaction with Eu （Ⅲ ）. Eu （ Ⅲ ） coordinates with DOPA and Dopamine through five-member chelate tings via carboxylic oxygen and amino nitrogen. The electrode kinetic parameters viz, transfer coefficient （αna）, diffusion coefficient （D）, forward heterogeneous rate constant （ k^0 fh） were evaluated for Eu（ Ⅲ ）-DOPA/Eu（ Ⅲ ）-Dopamine. The results obtained were used to investigate the nature of interaction of Eu （Ⅲ） with muhi-donor biomolecules. The possible mechanism was also proposed.     

An E-plane ferrite loaded simple waveguide radiator

Experimental investigations were conducted to examine the effect of dielectric loading on a ferrite loaded waveguide radiator (notch antenna). The antenna was made by symmetrically tapering an X-band waveguide. A cylindrical ferrite post was disposed at the apex of the notch and it was biased with a dc magnetic field. The antenna was tested for several notch angles namely 140/spl deg/, 120/spl deg/, 90/spl deg/, 80/spl deg/, 60/spl deg/ while ferrite was loaded with several dielectric sleeves, such as wood, polymer, pyrex. The dielectric loading with high permittivity material is found to give better radiation and scanning characteristics. The radial thickness of the dielectric ring is observed to affect the radiation.     

When employees strike back: Investigating mediating mechanisms between psychological contract breach and workplace deviance.

In this article, psychological contract breach, revenge, and workplace deviance are brought together to identify the cognitive, affective, and motivational underpinnings of workplace deviance. On the basis of S. L. Robinson and R. J. Bennett's (1997) model of workplace deviance, the authors proposed that breach (a cognitive appraisal) and violation (an affective response) initiate revenge seeking. Motivated by revenge, employees then engage in workplace deviance. Three studies tested these ideas. All of the studies supported the hypothesized relationships. In addition, self-control was found to be a moderator of the relationship between revenge cognitions and deviant acts; the relationship was weaker for people high in self-control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transalkylation of toluene with C9 aromatic hydrocarbons over ZSM5 zeolites

The transalkylation reactions of a mixture of toluene and C₉⁺ aromatics were studied over HZSM5 catalysts of varying SiO₂:Al₂O₃ ratios (30–800) as well as over a NiHZSM5 catalyst. As the SiO₂: Al₂O₃ ratio is increased, the rate of transalkylation is decreased. Among the C₉ aromatics that were present in the feed, the ethyl toluenes were extensively de-ethylated to toluene. The shape-selective characteristics of the ZSM5 zeolite were revealed through the relative order of reactivity of the three trimethyl benzene isomers 1.2.4>1.2.3>1.3.5. The stable life of the catalyst can be prolonged by the incorporation of nickel. The influences of process parameters such as temperature, pressure, space velocity and H₂: hydrocarbon ratio are also presented. It was observed that the transalkylation of C₉ aromatics with toluene to yield xylenes occurs mainly on the external surface of the ZSM5 crystals. The disproportionation of toluene to yield benzene and xylene, however, takes place predominantly in the pore system.     

Low voltage current mirrors with enhanced bandwidth

This paper presents an improved low voltage cascode and flipped voltage follower (FVF) based current mirror with the enhancement of the bandwidth obtained by using a compensation resistor between the gates of the primary transistor pair. In this technique a carefully determined resistance is used in the diode connected MOS transistor of the current mirror for enhancing the bandwidth. Active realization of the compensation resistance using MOS operating in the triode region has also been applied to both the cascode and FVF based current mirror circuits. The proposed circuits have been simulated using PSpice for 0.25 μm CMOS technology and the obtained results are compared with their uncompensated topologies to show their effectiveness.