An X-ray photoelectron spectroscopic investigation into the chemical structure of deposits formed from hexamethyldisiloxane/ oxygen plasmas

The effect of oxygen addition to microwave-sustained plasmas of hexamethyldisiloxane (HMDSO) has been investigated. Attention was directed to the solid products formed on aluminium substrates (plasma deposits). To enable a quantitative analysis of these, X-ray photoelectron spectroscopy (XPS) of standard silicon-containing materials was carried out. When suitable charge correction is applied to the XP spectra of HMDSO/O₂ plasma deposits, a number of very clear trends emerge. From changes in elemental composition, core line binding energies (Si2p, C 1s, and O 1s) and widths, we show how oxygen addition to the plasma affects the chemical nature of the plasma deposit. The data reported also provide (some limited) information on the reactions taking place in the plasma.     

Effect of titanium substitution on the structure and properties of Fe3Al-based intermetallic alloys

Substitutions (0–16 at%) of titanium for iron in Fe₃Al-based alloys rapidly solidified by chill-block melt-spinning stabilize the D0₃ and B2 ordered structures. Rapid solidification results in total suppression of D0₃ order in binary alloys, whereas alloys containing titanium have D0₃ structure. D0₃ and B2 antiphase domain size, lattice parameter and hardness increase with increasing titanium content of the alloy. The deformation mode changes from single (unit) bcc dislocation in binary alloys to two-fold superdislocation configuration in D0₃Fe₃Al-Ti alloys. Mechanical antiphase boundaries are generated by the movement of these imperfect configurations. All the alloys exhibited cleavage tensile failure. The mechanical properties are correlated with the observed structural changes.     

MQW wavelength-tunable DBR lasers with monolithically integrated external cavity electroabsorption modulators with low-driving voltages fabricated by selective-area MOCVD

The design and operation of multiple-quantum-well (MQW) wavelength-tunable distributed Bragg reflector (DBR) InGaAs QW lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area MOCVD are presented. Uncoated devices exhibit CW threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices also exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibited high extinction ratios of 40 dB at a modulator bias of 1.25 V.     

Evaluation of a commercial process for collection and cooling of beef offals by a temperature function integration technique.

The hygienic adequacy of a commercial process for the collection and cooling of beef offals was assessed by a temperature function integration technique. The diverse operations for collection of offals were inspected. The rates of product movement through those operations, and the temperatures of products at the time of their being packed, were determined. From that information, four of the nine product types were selected for examination of their temperature histories during the assembly and cooling of the cartoned products. The products selected encompassed product at near-body and near-air-ambient temperatures at the time of packaging, product in the largest and smallest cartons used in the process, and product with relatively short and long residence times in an unchilled carton stack assembly area. Twenty-one temperature histories were collected for each of the products, and the possible proliferation of an indicator organism, Escherichia coli, calculated for each temperature history. The results were assessed against a temperature function integration criterion derived from studies of beef carcass and cartoned meat cooling processes. Products packaged at near-ambient temperature readily met with the criterion, but products packed at near-body temperatures did not comply. The latter non-compliance was extreme for product packaged in large cartons. However, the principal cause of non-compliance was identified as highly variable cooling conditions in the carton freezing facility. A brief survey of air speeds and temperatures within that facility indicated means by which product cooling could be better controlled.     

Modelling direct sequence pseudonoise(dspn) satellite reception with directional antennas in the dense scatterer mobile environment

A geometric propagation model is developed for simulating the reception of direct sequence pseudonoise (DSPN) satellite signals by a directional or omni antenna in the dense scatterer mobile environment. The model is first validated for narrowband signals by a direct comparison of both simulated cumulative signal strength statistics and simulated diffuse Doppler spectra with classical theory. The model is then used to predict fading statistics for DSPN signaling, either with omni or directional antennas. As expected, the mitigation of fading is closely related to the ratio of DSPN chip duration to delay spread of the scatterer medium for both the omni and directional antennas.