Simultaneous nonlinear absorption and index effects in the propagation of intense TEA CO2 laser pulses through CDF3

Changes in the beam profile of the CO2 laser 10R(26) line, caused by transmission through, and absorption by, CDF3 were studied using an array of pyroelectric detectors. During the propagation of the laser beam through CDF3, nonlinear absorption and self-defocusing of the beam have both been determined from measurements of the effect on the exit beam of fluence, radiant energy, CDF3 pressure, transmission cell length, and distance from the exit of the cell to the detector array.     

Creep of CaO/MgO refractories

The creep properties of a standard doloma brick (containing 40% MgO) and a magnesia-enriched doloma product (containing 60% MgO) have been compared with the behaviour of CaO-MgO samples having compositions and microstructures similar to those of the pellet raw materials used for manufacture of the fired doloma refractories. The creep strength is shown to be improved not only by magnesia enrichment but also by reducing the impurity levels, particularly the Fe₂O₃ content.     

Thermal shock of ß-alumina with zirconia additions

Sodium-alumina electrolyte tubes were prepared from spray dried precursor powders with additions of 2, 5, 10 and 15 wt % ZrO₂ made by the sodium zirconate route. The thermal shock behaviour of ring segments cut from the tubes was examined by quenching into water at 0° C. At the 2% ZrO₂ level the dispersed ZrO₂ particle size was low, <0.5m, and the tetragonal phase was retained. For higher weight fractions, particle coarsening during the-alumina sintering schedule was extensive and the large particles transformed to monoclinic on cooling. At the 15% ZrO₂ level the-alumina had a slightly reduced strength and high resistance to thermal shock and to thermal shock damage, quenching into water from 800° C effecting only a 43% reduction in strength. These observations are consistent with the effects of microcracking in the vicinity of second phase ZrO₂ particles.     

Mode matching for a passive resonant ring laser gyroscope

An analytical method of matching the mode of an input laser to the lowest-order mode of a passive resonant ring laser gyro is described, as are the steps in determining the location and focal length of cylindrical mode matching lenses. Results were obtained with no mode matching, with a compromise spherical lens, with horizontal mode matching only, and with the proper cylindrical mode matching lenses. Compared with no mode matching, the latter case shows that the amplitude of the lowest-order mode is increased approximately 2.5 times. In addition, the number and intensity of higher-order modes are reduced to near zero, and the relative intensity of the lowest-order mode to the higher-order mode increased from approximately 5 to approximately 60 times greater.     

Light on! Real world evaluation of a P300-based brain-computer interface (BCI) for environment control in a smart home

Brain-computer interface (BCI) systems aim to enable interaction with other people and the environment without muscular activation by the exploitation of changes in brain signals due to the execution of cognitive tasks. In this context, the visual P300 potential appears suited to control smart homes through BCI spellers. The aim of this work is to evaluate whether the widely used character-speller is more sustainable than an icon-based one, designed to operate smart home environment or to communicate moods and needs. Nine subjects with neurodegenerative diseases and no BCI experience used both speller types in a real smart home environment. User experience during BCI tasks was evaluated recording concurrent physiological signals. Usability was assessed for each speller type immediately after use. Classification accuracy was lower for the icon-speller, which was also more attention demanding. However, in subjective evaluations, the effect of a real feedback partially counterbalanced the difficulty in BCI use. PRACTITIONER SUMMARY: Since inclusive BCIs require to consider interface sustainability, we evaluated different ergonomic aspects of the interaction of disabled users with a character-speller (goal: word spelling) and an icon-speller (goal: operating a real smart home). We found the first one as more sustainable in terms of accuracy and cognitive effort.     

A Computer-Based Brain Stimulation System to Investigate Sensory Prostheses for the Blind and Deaf

Electrical stimulation of the visual cortex of the brain results in punctate photic sensations called ``phosphenes.' This suggests the concept of producing artificial vision for the blind by implanting arrays of electrodes, producing scoreboard-like displays. Electrical stimulation of the cochlea, VIIIth nerve, and auditory cortex produces analogous auditory sensations called ``audenes,' which might be used to provide artificial hearing for the deaf.     

Modelling of food transportation systems – a review

In 2002, over a million refrigerated road vehicles, 400,000 refrigerated containers and many thousands of other forms of refrigerated transport systems are used to distribute chilled and frozen foods throughout the world. All these transportation systems are expected to maintain the temperature of the food within close limits to ensure its optimum safety and high quality shelf life.Increasingly, modelling is being used to aid the design and optimisation of food refrigeration systems. Much of this effort has concentrated on the modelling of refrigeration processes that change the temperature of the food such as chilling, freezing and thawing. The purpose of a refrigerated transport system is to maintain the temperature of the food and appears to have attracted less attention from modellers. This paper reviews the work that has been carried out specifically on the modelling of food temperature, microbial growth and other parameters in the transportation of food.     

Use of fluorescence to probe the surface dynamics during disorder-to-order transition and cluster formation in dihalonaphthalene-water thin films on Al2O3(0001)

Amorphous dihalonaphthalenes that are prepared by vacuum deposition onto a cold Al₂O₃ surface form electronically excited dimers when optically pumped, and their emission is characteristically red-shifted, broad and featureless compared to the monomeric fluorescence. If the surface is heated, the adlayer undergoes a disorder-to-order transition at a temperature characteristic of the molecule. Since pure crystalline dihalonaphthalenes typically fluoresce and do not exhibit excimeric features, the transition was studied by taking advantage of the changes in the spectral characteristics of the adlayer. These included transmittance, and emission from fluorescence and excimer. The combination of these methods allowed a close look at the surface dynamics of molecules on the surface of Al₂O₃ as the adlayer was heated from the deposition temperature to desorption.If a bilayer is formed by depositing water onto the surface with the organic adlayer on top, water, with its lower desorption energy, can be made to percolate into the organic layer. The optical probes indicate that the water clearly associates with the organic molecules while the excess water desorbs. By varying the coverage of either the water or the dihalonaphthalene, the stoichiometric composition of the cluster can be determined and are reported here.