Influence of chemical trace additives on the future ageing of the UA1 central detector

A number of systematic tests investigating the effect of various chemical additives on the ageing of prototypes of the UA1 Central Detector have been performed. In addition to the classical substances of water, ethanol and isopropanol emphasis is also put upon more uncommon chemicals, usually required as doping seeds for UV laser calibration. Chamber lifetime can be strongly influenced by them, depending on their concentration. Evidence is presented that proper choice and dosage can lead to a significant extension of normal wire chamber lifetime.     

Optical band gap shift in thin LiNbO3 films grown by radio-frequency magnetron sputtering

Thin polycrystalline LiNbO₃ films were deposited by the radio-frequency magnetron sputtering (RFMS) method and ion-beam sputtering (IBS) method under different conditions. Study of the adsorption band edge of fabricated films reveals direct and indirect optical transition. Depending on the particular technological sputtering RFMS regime, the direct energy gap varies from 3.8 to 4.4 eV. Band tails induced by the defects formation due to the reactive plasma effect on the film structure are responsible for indirect optical transitions in the studied films. Thermal annealing has a prominent effect on trap concentration and strain in as-grown films leading to rise in direct band energy up to 4.4 eV which is close to the value for bulk LiNbO₃.     

Determination of the temperature profile of axisymmetric combustion-gas flow from infrared spectral measurements

A numerical iteration technique for determining both the temperature and CO₂ concentration profiles of axisymmetric combustion-gas flow from low resolution infrared spectral measurements has been developed. The technique includes inversion of the temperature profile from emission measurements when the CO₂ concentration distribution is known, inversion of the CO₂ concentration profile from transmittance measurements when the temperature distribution is known, and inversion of both temperature and CO₂ concentration profiles simultaneously from emission and transmittance data of the combustion-gas flow. The iteration technique is accurate, efficient, and effective even under structured temperature distributions. The effects of temperature, optical thickness, wave number, and band model parameters on the determined profiles are analyzed. It is found that a deviation of 40% in CO₂ concentration results in a difference of only about 5% in the determined temperature profile. This implies a possibility of passive scanning. The determined temperature profile of a laboratory combustion-gas flow agrees well with probe measurements.     

The frictional interface: a tribological approach of thermal misfit,surface roughness and sliding velocity effects

In ceramic matrix composites, it is now well known that the cyclic fatigue effects are due to a decrease of the stress transfer capability of the fibres that bridge the matrix cracks, because of some wear induced by the seesaw displacements at the interfaces. Therefore, a better knowledge of the cyclic fatigue effects needs a deeper understanding of the microscale mechanisms operating during the friction between fibre and matrix. This is the main subject of the present paper which deals with single filament model composites submitted to push-out tests at room temperature under dry friction condition. Emphasis is placed here on the roughness of the slipping surfaces in relation with thermal misfit, and with sliding velocity.     

Corrosion evaluation of multi-pass welded nickel–aluminum bronze alloy in 3.5% sodium chloride solution: A restorative application of gas tungsten arc welding process

In this research, the corrosion behavior of a gas tungsten arc welded nickel–aluminum bronze (NAB) alloy is investigated by DC and AC electrochemical techniques in 3.5% sodium chloride solution. Regarding the electrochemical impedance spectroscopy and potentiodynamic results, uniform corrosion resistance of instantly immersed weld and base samples are almost analogous and increased (more in weld region) during the immersion times. Moreover, zero resistant ammeter results demonstrated that the few nanoampere galvanic currents are attributed to microstructural and morphological differences between these two regions. Therefore, the welding procedure could not deteriorate the general corrosion resistance of the restored damaged NAB parts operating in marine environments.     

Combining DPSK and duobinary for the downstream in 40-Gb/s long-reach WDM-PONs

We propose and demonstrate combining differential phase-shift keying (DPSK) and duobinary transmission for the downstream in 40-Gb/s long-reach wavelength division multiplexed-passive optical networks (WDM-PONs) in order to provide robust transmission performance in the backhaul section and simple detection at the ONUs. DPSK is deployed in the trunk span as it provides stronger robustness to fiber nonlinearity. Duobinary is used in the access span where its higher chromatic dispersion tolerance relieves the need for dispersion compensation. All-optical multichannel modulation format conversion from DPSK to duobinary is realized in the local exchange in a single delay interferometer to reduce system cost. Single and multi-channel 80-km long-reach DPSK transmission and up to 5-km duobinary access transmission are experimentally demonstrated at 40 Gb/s. The proposed approach shows great potential for future high data rate optical access networks.     

Un nouvel outil pour l'étude des interactions tôle–outil–lubrificant: Le test en cadence

In order to obtain a formed part, free from any defect such as necking, failure, galling marks or bad surface appearance, it is increasingly important to control the deep interactions between the steel sheet, the lubricant and the tooling. Another fundamental requirement for the industry is an ever growing productivity which implies a better stability of the process, also allowing an increase in the number of parts drawn per minute. Recently, RDCS has developed a new friction set-up able to study the behaviour of the steel sheet, coated or not, during its short contact with the tooling in the presence of a lubricant. Series of hundreds of samples are successively drawn. First results are interpreted.