Transmission Fiber Chromatic Dispersion Dependence on Temperature: Implications on 40 Gb/s Performance

In this letter, we will evaluate the performance degradation of a 40 km high‐speed (40 Gb/s) optical system, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters.     

Infrared and ultraviolet–visible spectroscopic studies of silica, [(Cp)2ZrCl2] and trimethylaluminum interactions

Infrared and UV–vis studies of metallocene immobilization on silica are reported here. The results have indicated changes in the Zr coordination sphere of metallocene depending on the immobilization route used. The reaction of [(Cp)₂ZrCl₂] with silica formed [(Cp)₂ZrCl]⁺[SiO]⁻ species. The same metallocene, reacting with TMA modified silica, formed monomethylated and dimethylated species by the substitution of chloro for methyl ligands, stabilized on the surface by interaction with “MAO-like” species (methylaluminoxane, MAO). These monomethylated and dimethylated cationic zirconium species are the active centers for the polymerization reaction. Different order of TMA addition in the silica modification step generated surface species of a similar nature, differing in their relative quantities. The highest amount of these active species was obtained when the support was added to the TMA solution rather than adding the TMA solution to the silica support. This was the most significant parameter affecting catalytic activity in ethylene polymerization.     

Robustness issues in optimal control of unstable plants

This paper presents a robustness analysis of the optimal solution of the step tracking problem in a one-degree of freedom control architecture, for the discrete-time multivariable (MIMO) case. It is shown that the resulting closed loop becomes arbitrarily fragile, i.e. the sensitivity peak becomes arbitrarily large, for certain reference directions. The cause of this problem is that the optimal controller depends on the reference direction. The paper shows that this dependence can be eliminated with an alternative formulation of the optimal problem where the cost is averaged over all reference directions.     

Thermodynamics of gas-solid flow

New thermodynamic fundamentals for vertical pneumatic conueying are proposed with derivation based strictly on mass conservation and continuum concept. For a 1-D, vertical, steady gas-solid flow, these new mass and energy balances allowed the derivation of a new nondimensional energy factor containing the pressure drop. This energy factor correlated quite well with the difference between the inlet gas velocity and solids terminal velocity, when tested against high-pressure, 15-m-high, vertical pneumatic transport data from Institute of Gas Technology. The energy factor was also checked against atmospheric-pressure data of the 5-m lift line of the Pennsylvania State Uniuersity. The new energy factor covers quite well both the atmospheric- and high-pressure sets of data (923 tests) including two heights, lean- and dense-phase transports, several pipe diameters, broad and narrow particle-size distributions, and different materials. The dissipation terms in gas-solid flow were also clearly identified.     

Extrusion-rotomolding of plasticized PVC formulations

In this work, we present a novel process to produce plasticized PVC articles. Plasticized PVC dispersion resin (dry blend) was extruded and poured into a hot mold. The mold was transferred to a rotomolding machine, where the final geometry was obtained. Formulations using commercial PVC suspension resin and three different types of plasticizers were prepared under different processing conditions. The physical appearance of the articles and the tensile properties of the materials were evaluated.     

HIV training and perceived competence among doctoral students in psychology.

A training-needs assessment was conducted at California School of Professional Psychology, Berkeley/Alameda, on students' beliefs about clinical competence, past training in HIV issues, and future training needs at the school. They perceived themselves to be somewhat competent in providing clinical services to HIV patients and members of groups at high risk for HIV. A modest correlation was found between the students' total HIV training and perceived competence, but none was found between the multicultural emphasis in HIV education and their perceived competence. These findings suggest an ethical dilemma surrounding inadequately trained psychologists providing services to multicultural populations. Ethical issues concerning training standards and criteria for clinical competency are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A typology of propagation of changes on the structure of a multiregional economic system: the case of the European Union, 1975–1985

The effects of structural change in all sectors of some regions in multiregional input-output systems are explored in this paper. For each region, the changes in direct inputs are decomposed into a matrix of intraregional changes and a matrix of interregional backward linkage changes. This distinction provides for a decomposition of changes in the Leontief inverse into a sum of matrices representing the matrices of intraregional and interregional fields of influence of changes. In turn, this process facilitates the identification of changes in gross outputs that may be traced to changes in intra- and interregional structural changes. The analysis is applied to the European input-output tables for 1975 and 1985.This paper was presented at the 1996 annual meeting of the Western Regional Science Association     

Computationally efficient methods for bit-error rate evaluation inweakly coherent optical systems

A semianalytical method to estimate the bit-error rate performance of nonsynchronous ASK and FSK optical heterodyne systems is presented. This approach takes into account numerous system details with an accuracy similar to Monte-Carlo simulation, but with a computation time reduced by several orders of magnitude. An analytical approximation, based on a closed-form expression for the decision variable moment generating function, is also presented. The results obtained with the semianalytical method and the analytical approximation are compared to Monte-Carlo simulation results and to measurements obtained on a practical FSK system     

Uniform Polarization Scattering With Fiber-Coil-Based Polarization Controllers

A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions     

Mycological survey for potential aflatoxin and ochratoxin producers and their toxicological properties in harvested Brazilian black pepper.

A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis.