Properties of feedback solitons in a single-mirror experiment

We report on the observation of localized states (LSs) in a single-mirror feedback system using sodium vapor as the nonlinear medium. By combining experimental results with simulations based on a microscopic model and with results of a linear stability analysis of the homogeneous state, we discuss the properties of the LSs, the mechanism of their formation, their domain of existence in parameter space, their interaction with the amplitude and phase gradient in the Gaussian beam of the driving laser, and the formation of "molecules" and "clusters" of LSs. We elucidate the dominant role of diffraction in the interaction of the LSs and discuss relations between the clusters of LSs and extended patterns.     

QoS enhancement for adaptive streaming services over WCDMA

This paper presents a new method to adapt the quality-of-service (QoS) in a wideband code-division multiple-access (WCDMA) system, called radio network feedback (RNF). The concept of RNF is in general applicable to all the services requiring a minimum quality (i.e., non best effort) and in this paper, the focus is on streaming. In this context, RNF makes it possible for a streaming server to adapt its source bit rate to a WCDMA radio link, whose bandwidth may vary in time due, for example, to decongestion/congestion situations over the air interface or to handover. This is very beneficial for the end user as it allows to increase the bandwidth (i.e., the quality) when possible and to decrease it (instead of just dropping the service) when needed. RNF was compared with Client-based adaptation solutions. Simulation results show that RNF is fast and accurate and performs better than Client-based adaptation. For example, rebuffering occurs only with Client-based method. Moreover, with RNF the up-switch is performed only when needed, whereas the up-switch performed by means of the Client-based method is often erroneous and may annoy the end user.     

Photoswitching of Ferroelectric Liquid Crystals Using Unsymmetrical Chiral Thioindigo Dopants: Photoinduced Inversion of the Sign of Spontaneous Polarization

A new unsymmetrical chiral thioindigo dopant 6‐[(R,R)‐2,3‐difluorooct‐1‐yloxy]‐5′‐nitro‐6′‐[(R)‐2‐octyloxy]thioindigo ( 4 ) designed to photoinvert the sign of spontaneous polarization (P_S) in a ferroelectric chiral smectic C (SmC*) liquid crystal was prepared using a synthetic approach previously developed in our laboratory. In this new “ambidextrous” design, the (R)‐2‐octyloxy side‐chain is sterically coupled to the thioindigo core and induces a positive P_S, whereas the (R,R)‐2,3‐difluorooctyloxy side‐chain is decoupled from the core and induces a larger negative P_S. In the trans form, this dopant induces a negative polarization in the SmC host (+)‐4‐(4‐methylhexyloxy)phenyl 4‐decyloxybenzoate ( PhB ). Irradiation of a 1 mol‐% mixture of 4 in PhB at λ = 510 nm caused a sign inversion of P_S, from –0.88 to +0.42 nC cm^–2 at T – T_C = –5 °C, which is consistent with an increase in the polarization power of the coupled 2‐octyloxy/thioindigo unit over that of the 2,3‐difluorooctyloxy unit, due to the increase in transverse dipole moment of the thioindigo core upon trans–cis photoisomerization. The P_S sign inversion was confirmed by a surface‐stabilized ferroelectric liquid crystal photoswitching experiment. Spectroscopic measurements on films of the doped liquid crystal mixtures showed that trans–cis photoisomerization is gradually suppressed with increasing dopant mole fraction, possibly as a result of increased dopant aggregation.     

Modeling Temperature in Coupled Electrical and Thermal Simulations of the Electroconsolidation® Process

Electroconsolidation® is a process for densifying complex-shaped parts by using electrically conductive particulate solids as a pressure-transmitting medium. The part is immersed in a bed of the particulate medium contained in a die chamber. Sintering temperature is achieved by resistive heating of the medium while applying compaction pressure. The process is capable of ultrahigh temperatures and short cycle times and offers the potential for low processing costs.

Control of the process and selection of process conditions require knowledge of the temperatures within the die. Temperature gradients exist because of the high heating rate and because of variations of density and electrical resistivity of the medium due to the presence of the part. Direct measurement of temperature with thermocouples or other conventional means is impractical because of the high temperatures, high currents, and high pressures that are involved. Therefore, a computer model was developed to predict temperature as a function of time and applied voltage for any location in the die. The computer model is composed of three parts: a geometrical model to approximate the density and resistivity variations in the medium, a finite-element model to calculate the rate of resistive heating within each element, and a finite-difference model to calculate the temperature distribution based on solution of the heat-transfer equations. Predicted temperatures have been shown to be in excellent agreement with measurements, and numerical simulation provided encouraging consistency and reasonably accurate predictions of temperature profiles within the die. The model demonstrated the feasibility of a new process to achieve simultaneous application of pressure and heat to powder densification in Electroconsolidation.     

High‐pressure processing effects on the mechanical,barrier and mass transfer properties of food packaging flexible structures: a critical review

Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.     

New insights into the relation between channel hot carrier degradation and oxide breakdown short channel nMOSFETs

In this letter, we report new findings in the relation between channel hot-carrier (CHC) degradation and gate-oxide breakdown (BD) in short-channel nMOSFETS biased at V/sub G/>V/sub D/. We observe that the time-to-BD is strongly reduced in the hot carrier regime and that although the channel hot-electron injection into the oxide occurs mainly at the drain side, stress-induced leakage current (SILC) generation and oxide BD always occur at the source side. The results of these measurements indicate that not solely the energy of the injected electrons but also the oxide electric field is determinant in the oxide BD process.     

Optoviscosimetry of a Liquid Film by the Method of a Dispersed Magnetic Sublayer

A magnetooptical method of measurement of viscosity, which is based on recording the optical response (induced by the magnetic-field pulses) of a two-layer system resulting from the sedimentation of ferroparticles dispersed in the liquid under study, has been proposed. The procedure has been described and the results of measurement of the rheokinetics of a number of media, including polymer compositions formed into a thin film, in heating, evaporation, and polymerization have been presented.