Full polarization insensitivity of a 20 Gb/s strained-MQWelectroabsorption modulator

We report on a MQW electroabsorption modulator with tensile-strained wells. The device transmission is shown to be fully polarization insensitive, i.e. both in amplitude and phase. The modulation efficiency is over 20 GHz/V (bandwidth higher than 20 GHz and 1 V drive voltage) which is the highest figure of merit reported for any kind of polarization insensitive modulator. Full polarization independence is further demonstrated by 2.5 Gb/s transmission at 1.55 μm over 475 km of standard fiber without penalty at 10^-9 BER whatever the polarization     

Spectral Representation for a Class of Non-Gaussian Processes

A new model is developed for non-Gaussian processes. The model is based on the spectral representation theorem for weakly stationary processes, can match the second moment properties and several higher order moments of any non-Gaussian process, and consists of a superposition of harmonics with uncorrelated but dependent random amplitudes. The calibration of the model to a target non-Gaussian process may require iterations. The It? formula is used to calculate higher-order moments of the proposed model. These moments can be used to tune the model such that it matches some of the higher-order moments of a target non-Gaussian process in addition to its second-moment properties. The proposed model is useful for both Monte Carlo simulation and analytical studies on the response of linear and nonlinear systems to non-Gaussian noise. Examples are presented to illustrate the use of the proposed model.     

Probabilistic Model for Polycrystalline Microstructures with Application to Intergranular Fracture

A two part probabilistic model for polycrystalline microstructures is described. The model utilizes a Poisson–Voronoi tessellation for the grain geometry and a vector random field model for the crystallographic orientation. The grain geometry model is calibrated to experimental data through the intensity of the Poisson point field underlying the Poisson–Voronoi tessellation and the orientation random field is calibrated to experimental data through its marginal distributions and second moment properties. Realizations of the random microstructure are generated by use of translation methods and are used, with simplified mechanical models, to investigate the problem of intergranular fracture. It is found that intergranular cracks exhibit some statistical properties of a scaled Brownian motion process.     

Equivalent linearization for Poisson white noise input

Methods are developed for calculating characteristic functions and mean upcrossing rates of the response of linear systems to α-stable input processes. The methods are based on the integral and series representations of these processes. The integral representation resembles the spectral representation of wide-sense stationary processes. The α-stable processes are non-Gaussian and have no moments of order two and higher. Therefore, classical methods of linear random vibration for calculating the mean and covariance functions of the response from the corresponding functions of the input do not apply. Applications are presented to illustrate the proposed methods of analysis.     

Linear random vibration by stochastic reduced‐order models

A practical method is developed for calculating statistics of the states of linear dynamic systems with deterministic properties subjected to non‐Gaussian noise and systems with uncertain properties subjected to Gaussian and non‐Gaussian noise. These classes of problems are relevant as most systems have uncertain properties, physical noise is rarely Gaussian, and the classical theory of linear random vibration applies to deterministic systems and can only deliver the first two moments of a system state if the noise is non‐Gaussian. The method (1) is based on approximate representations of all or some of the random elements in the definition of linear random vibration problems by stochastic reduced‐order models (SROMs), that is, simple random elements having a finite number of outcomes of unequal probabilities, (2) can be used to calculate statistics of a system state beyond its first two moments, and (3) establishes bounds on the discrepancy between exact and SROM‐based solutions of linear random vibration problems. The implementation of the method has required to integrate existing and new numerical algorithms. Examples are presented to illustrate the application of the proposed method and assess its accuracy. Copyright © 2009 John Wiley & Sons, Ltd.     

The relative effects of transection of the gustatory branches of the seventh and ninth cranial nerves on NaCl taste detection in rats.

Chorda tympani nerve (CT) transection in rats severely impairs NaCl taste detection. These rats can detect higher concentrations of NaCl, however, suggesting that remaining oral nerves maintain some salt sensibility. Rats were tested in a gustometer with a 2-response operant taste-detection task before and after sham surgery (n = 5), combined transection of the CT and the greater superficial petrosal nerves (GSP; 7x, n = 6), or transection of the glossopharyngeal nerve (GL; 9x, n = 4). Thresholds did not significantly change after sham surgery. Although the GL responds to NaCl and innervates nearly 60% of total taste buds, 9x surgery had no effect. However, 7x surgery increased NaCl detection threshold by ～2.5 log?? units, greater than that reported for CT transection alone. These results suggest that the GSP contributes to NaCl sensitivity in rats and also demonstrate that the GL and perhaps the superior laryngeal and lingual nerve proper can maintain some NaCl detectability at high concentrations. These findings confirm the primacy of the 7th nerve relative to the 9th nerve in sensibility of NaCl in the rat model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion regulation and decision making under risk and uncertainty.

It is well established that emotion plays a key role in human social and economic decision making. The recent literature on emotion regulation (ER), however, highlights that humans typically make efforts to control emotion experiences. This leaves open the possibility that decision effects previously attributed to acute emotion may be a consequence of acute ER strategies such as cognitive reappraisal and expressive suppression. In Study 1, we manipulated ER of laboratory-induced fear and disgust, and found that the cognitive reappraisal of these negative emotions promotes risky decisions (reduces risk aversion) in the Balloon Analogue Risk Task and is associated with increased performance in the prehunch/hunch period of the Iowa Gambling Task. In Study 2, we found that naturally occurring negative emotions also increase risk aversion in Balloon Analogue Risk Task, but the incidental use of cognitive reappraisal of emotions impedes this effect. We offer evidence that the increased effectiveness of cognitive reappraisal in reducing the experience of emotions underlies its beneficial effects on decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A decoupled sliding mode control for a continuum arm

The paper treats the control problem of a class of robots constituted by a chain of continuum segments. The technological model basis is a central, long and thin, highly flexible and elastic backbone. The segment control system is a decoupled one. The main parameters of the arm control are determined by the curvature and curvature gradient. The dynamic model is inferred. The primary benefit of the proposed method is that the dynamic equations are represented by a set of ODE’s in time instead of PDE’s in time and space, and the new curvature gradient lumped parameter model is used. A sliding mode control system is used in order to achieve the desired shape of the arm. The stability of the closed-loop control system is proven. Numerical simulations and an experimental platform are also provided to verify the effectiveness of the presented approach.     

Rheological Aspects of Spanish Honeys

The purpose of this work was to investigate the rheological behavior of Spanish honeys under different conditions (at different temperatures and concentrations). All the samples were characterized to determine their physicochemical (moisture, ⁰Brix, pH, ash, conductivity, color, total acidity, diastase activity, 5-hydroxymethylfurfural content, sugar content) and thermal (glass transition temperature) profiles. The honeys samples (80.4–82 ⁰Brix) behaved as Newtonian fluid; as expected, their viscosity increased with the solid content and decreased with the temperature. Two experimental viscosity models (Arrhenius and Vogel–Taumman–Fulcher) were checked using the experimental data to correlate the influence of temperature on honey viscosity. A simplified model was proposed to describe the combined effect of the temperatures and concentrations (⁰Brix) on the viscosity of Spanish honeys. The dynamic viscosity and complex viscosity had the same magnitude at 40 °C, 45 °C, and 50 °C for of all the samples and the Cox Merz rule could be applied at these temperatures.     

New use of size exclusion chromatography in kinetics of mechanical degradation of polymers in solution

A new method to investigate the mechanical degradation of polymers in solution is described that uses size exclusion chromatograms of the initial polymer and of the degraded sample. The incipient parts of these chromatograms are analyzed to obtain kinetic data about degradation at the level of infinitesimal fractions. The procedure is based on the fact that mechanical degradation of the polymers is a first-order reaction and macromolecules are cleaved mostly in their central region. The rate constant and the variation in the rate constant with molecular weight are determined in a single experiment, avoiding additional fractionation steps. Moreover, the slope of the size exclusion chromatographic calibration curve is derived, opening new ways to determine polydispersities or even to make rapid calibration for unknown polymers. To verify the method, the rate constant and the molecular weight dependence of the rate constant were determined for the sonic degradation of polystyrene in toluene. The rate constant is found to vary with the square of the molecular weight, and its value is in good agreement with results reported using much more laborious methods. © 1993 John Wiley & Sons, Inc.