Reducing the diffraction artifacts while implementing a phase function on a spatial light modulator

Spatial light modulators are often used to implement phase modulation. Since they are pixelated, the phase function is usually approximated by a regularly sampled piecewise constant function, and the periodicity of the pixel sampling generates annoying diffraction peaks. We theoretically investigate two pixelation techniques: the isophase method and a new nonperiodic method derived from the Voronoi tessellation technique. We show that, for a suitable choice of parameters, the diffraction peaks disappear and are replaced by a smoothly varying halo. We illustrate the potential of these two techniques for implementing a lens function and wavefront correction.     

Nanostructures in thermal spray coatings

The nature of the nanograins formed by high velocity oxy-fuel thermal spraying of (FeAl) milled powder has been investigated using transmission electron microscopy on cross-sectional thin foils. Equiaxed 3D nanometer crystallites are formed by recrystallization in the unmelted powder particles while 2D nanometer columnar grains are produced by rapid solidification within the fully molten splats.     

Recent achievements in the development of partitioning processes of minor actinides from nuclear wastes obtained in the frame of the NEWPART European programme (1996–1999)

Partitioning of long-lived minor actinides (americium and curium) from the nuclear wastes issuing the reprocessing of nuclear spent fuels, in order to transmute them into short-lived nuclides or to condition them into stable crystalline matrices, was the subject of intense research within the NEWPART research program of the European 4^th Frame Work Program, FWP (1996–1999). The target waste considered was the acidic raffinate (HAR) issuing the reprocessing of the used nuclear fuels by the PUREX process. A two step separation process based on liquid-liquid extraction was designed. The first step consists in the co-separation of the mixture of trivalent actinides and lanthanides from the HAR by extraction with a malonamide extractant (DIAMEX process), while the second step concerns the actinides(III)/lanthanides(III) group separation (SANEX process). Several DIAMEX and SANEX processes were developed and successfully tested with cold, spiked and genuine high active effluents. The research carried out also included basic and fundamental works in order to better understand the relationships between the structures of the extractants and their affinities for the target metal ions. The lecture highlighted both the basic and applied aspects of the research. This work will be pursued (PARTNEW program) within the 5^th FWP of the European Union during the period 2000–2003.     

A new and fast method to determine mixing and conductive cooling of thermal waters in carbonate-evaporite environments

A method is proposed, for low-temperature geothermal systems, for calculating the aquifer temperature and relative proportions of mixed thermal and shallow groundwaters from carbonate-evaporite environments. The fluid is assumed to be in chemical equilibrium with anhydrite and chalcedony in the aquifer, and mixed with diluted waters during its ascent. An attempt has been made to establish a relationship between reservoir temperature, the aqueous sulfate and silica contents of the mixed fluid, the proportion of the thermal end-member and the temperature of the adiabatic mixture. The method calculates mineral solubilities in the field context, calibrated on representative thermal springs. The method also considers the effects of conductive cooling.     

Vector Field Based Texture Mapping of Animated Implicit Objects

This paper shows that an adequate use of vectorfields can solve most inconsistencies related to texture mapping that appear in current animation and rendering systems based on implicit objects. The method used is based on the concept of a virtual skin. A skin with its own texture mapping is spread over an implicit object and is constrained to stick to the deformation of the implicit object. A vectorfield is used to compute the relationship between the motion of the skin and the deformation of the object. Visual and implementation issues are discussed with respect to typical applications of implicit objects in computer graphics.     

Interaction between a coke and a tar. 2. Limit of tar penetration in coke porosity

The limit of penetration of a given coal-tar pitch into two cokes during mixing of the coke and liquid tar has been studied. It was shown that tar penetration is limited by compression of gas occluded in pores. Mercury porosimetry of cokes and pyrolysed coke-tar mixtures as well as micrographs of cokes impregnated with tar allow one to estimate the limiting pore diameter of tar penetration into coke at ca. 6 μm for the system considered.     

Determination of state-of-discharge of zinc-silver oxide button cells. II. Impedance measurements

The prediction of the state-of-discharge of numerous types of Zn-Ag₂O button cells from six international manufacturers has been investigated using the impedance technique over an extended frequency range. The frequency responses at various states-of-discharge are presented and it is shown that the changes in impedance which result from discharging provide several potential parameters for the state-ofdischarge prediction. The complex impedance plot of the undischarged cells usually shows a fairly welldefined semicircle at high frequencies and a straight line with a slope between 40 and 50° at low frequencies. As discharge proceeds, the diameter of the semicircle increases and the overlap between the semicircle and the low-frequency straight line increases. The most attractive method would be to determine a parameter such as a characteristic relaxation frequency in the complex impedance plot. Unfortunately, no unambiguous characteristic parameter can be extracted due to the non-ideal shape of the impedance response at high frequencies. The determination of the diameter of the high-frequency semicircle has been faced with the same difficulties. The most reliable test was found to be the determination of either the phase of the impedance, or a corrected phase ^– taken from the high-frequency intercept. The proposed prediction is a go/no go indication on the basis of one- or two-frequency measurements for or, ^– respectively. The selection is made at 20–40% state-of-discharge. The charge withdrawn is negligibly small and the time of the test is between 1 and 100 s depending on the type of cell. A calibration is necessary for each cell dimension and each manufacturer. Some 10–16% of the types of cells investigated could not be selected successfully, mainly because of too large a dispersion of the electrical characteristics of the cells, especially for small newly developed types, and of the similarity of the ( and values in the low and high state-of-discharge in the appropriate frequency range. The latter difficulty arises from the difference of the frequency response between the undischarged and the partly discharged cells occurring at high frequencies.This is the second of a series of papers dedicated to Professor Ernest Yeager on the ocasion of his 60th birthday.