A kinetic model for the acid-oxygen pressure leaching of Ni–Cu matte

A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni₃S₂. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O₂ flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O₂ flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase.     

The interfacial microstructure of joined single crystal and polycrystalline alumina

The interfacial microstructures of 96 and 98% polycrystalline alumina joined with single crystal sapphire have been investigated in relation to the joining parameters. Joining has been evaluated based on either using a thin spin-on silica interlayer or by placing the alumina and sapphire in direct contact. The materials were joined by placing the coated or uncoated surfaces in contact and heating in the range of 1340–1475 °C with minimum external load. With the aid of a silica interlayer, sapphire and 98% polycrystalline alumina were successfully joined in 180 min at 1400 °C and above, while samples without a silica interlayer failed to join under these conditions. However, sapphire and 96% polycrystalline alumina were joined both with and without the use of silica interlayer. A variety of interfacial morphologies have been observed, including amorphous regions, fine crystalline alumina, and intimate contact between the sapphire and polycrystalline alumina.     

Evidence of flexoelectricity in polymer-dispersed liquid crystals

The linear electro-optic response of polymer-dispersed liquid crystal films has been studied. Micrometer-sized droplets of a cyanobiphenyl mixture (E7) were formed in a Norland Optical Adhesive 65 photopolymer by photopolymerization-induced phase separation. Samples with various average nematic droplet sizes were systematically investigated. The temperature dependence of the first-harmonic electro-optic spectra was obtained. Peculiar peaks and double peaks in the phase spectra were found at temperatures close to the clearing point. Samples with narrow distributions of droplet sizes were characterized by a double peak of the amplitude spectra in the low-frequency range. A flexoelectric origin of the first-harmonic spectra in confined nematic systems is discussed.     

Thermodynamics of Chemical Interactions in the CdTe–ZnTe–O2–C System during Melt Growth of Cd1 – x Zn x Te Crystals

Thermodynamic analysis is used to identify the possible chemical reactions of CdTe and ZnTe with the container material and gaseous atmosphere during Bridgman growth. Thermodynamic parameters of carbide and oxycarbide formation in the growth system are evaluated. The calculation results are consistent with the well-known fact that oxygen-containing impurities can be removed from the growth charge by calcination in hydrogen. Moreover, as shown in experiment, the removal of oxygen from the charge ensures a substantial decrease in the carbon content of the crystals.     

Phase regression approach for estimating the parameters of a noisy multifrequency signal

A novel approach for estimating the parameters of a multifrequency signal from discrete samples corrupted by additive noise is presented. An established mathematical model indicates that noise influence on the discrete phase and amplitude spectra is equivalent to additive phase and amplitude noise, respectively. On this basis, a simple algorithm is proposed to estimate the frequency and phase of each sinusoid component by linear regression on the phase spectra of segmented signal blocks, while an amplitude estimator is directly derived from the spectrum of the window function. The circular nature of the phase spectrum is thoroughly explored. Also, an algorithmic scheme is presented. The derived variances of the estimators show that for a noisy signal this approach provides superior accuracy over the traditional approaches. Simulations and engineering application confirm the validity of the presented method.     

Cyclic mode of neptunium, americium and curium transmutation in heavy-water reactor

Characteristics of process of transmutation of neptunium, americium and curium from spent nuclear fuel in heavy-water reactor during first 10 lifetimes and at transition to equilibrium mode are calculated. During transmutation, dangerous nuclides, first of all, ²⁴⁴Cm and ²³⁸Pu are accumulated. They cause an increase of radiotoxicity. At first 10 cycles of transmutation, the radiotoxicity is increased by 8.7 times in comparison with radiotoxicity of initial load of transmuted actinides. Heavy-water reactor with thermal power of 1000 MW can transmute neptunium, americium and curium extracted from 3.7 VVER-1000 type reactors. It means, that the required power of transmutation reactor makes about 8% of thermal power of VVER-1000 type reactors.     

Presenting information on the small-screen interface: effects of table formatting

This study explored strengths and limitations of table formatting choices by engaging twenty-eight participants in information searches in online tables, presented on a small-screen interface (Palm IIIc). Table length across conditions was held constant at three screens long (24 rows total) but varied from one to three screens wide (approximately 35, 70, and 105 characters per line). Target information was positioned in either the upper left, lower left, upper right, or lower right quadrants. Data collected were time on task, error rate, and level of participants' confidence in their answers. Experimenters found that increased horizontal scrolling imposed the heaviest burden on information search. This study supports restricting table widths to one screen on handheld computers. If necessary, however, tables can go to two screens wide without critical detriment to usability. While ruled line formatting is slightly better than interface character in providing visual support for the burden of horizontal scrolling, neither formatting option adequately compensates for the added burden.     

Optimization of a photopolymerizable holographic recording material based on polyvinylalcohol using angular responses

Acrylamide-based holographic recording materials have significant advantages and the composition of these materials has been optimized in terms of energetic sensitivity and diffraction efficiency. As a result, diffraction gratings with an efficiency of almost 80% for energetic exposures of 35 mJ/cm² and a spatial frequency of 1000 lines/mm in photosensitive films 65 μm thick have been obtained. In this paper we present the effects of intensity, thickness, and variation in the concentration of each component by studying the angular responses of the diffraction gratings recorded in each composition.     

1.6 Tbit/s (40/spl times/40 Gbit/s) DPSK transmission over 3/spl times/100 km of TeraLight fibre with direct detection

By transmitting 40 channels over 300 km of TeraLight fibre, it is shown that optical differential phase shift keying can be used in 100 GHz-spaced 40 Gbit/s systems, with direct detection and a simple receiving filter. Chromatic dispersion tolerance around 300 ps/nm is also measured, compared to 70 ps/nm for NRZ.     

Programmable group-delay module using binary polarization switching

We demonstrate the first programmable group-delay module based on polarization switching. With a unique binary tuning mechanism, the device can generate any differential group delay value from -45 to +45 ps with a resolution of 1.40 ps, or any true-time-delay value from 0 to 45 ps with a resolution of 0.7 ps. The delay varying speeds for both applications are under 1 ms and can be as fast as 0.1 ms. We evaluate both the dynamic and static performances of the device while paying special attention to its dynamic figures of merit for polarization-mode dispersion emulation and compensation applications. Our experiment shows that the device exhibits a negligible transient-effect induced power penalty (<0.2 dB) in a 10-Gb/s nonreturn-to-zero system.