Reduction-diffusion method

The reduction-diffusion method is another method to prepare fine powders (around 20-50 pm) of alloys with low lattice strain because the alloy is prepared by heating the mixture of mischmetal oxides, the reductant (Ca) and the metal powder, such as Ni, Co, Mn, Al, at 900-1000 C (Takeya et al. 1993). Almost the same electrode performances as those of the samples prepared by the melting method were obtained for the Mn-containing alloys. 

Calciothermic reduction of samarium oxide, in the presence of cobalt powder, yields samarium-cobalt alloys in the powder form. The process is popularly known as reduction diffusion. Samarium oxide, mixed with cobalt powder and calcium hydride powder or calcium particles, is heated at 1200 °C under 1 atm hydrogen pressure to produce the alloys. Cobalt oxide sometimes partly replaces the cobalt metal in the charge for alloy preparation. This presents no difficulty because calcium can easily reduce cobalt oxide. A pelletized mixture of oxides of samarium and cobalt, cobalt and calcium, with the components taken in stoichiometric quantities, is heated at 1100-1200 °C in vacuum for 2 to 3 h. This process is called coreduction. In reduction diffusion as well as in coreduction, the metals samarium and/or cobalt form by reduction rather quickly but they need time to form the alloy by diffusion, which warrants holding the charge at the reaction temperature for 4 to 5 h. The yield of alloy in these processes ranges from 97 to 99%. Reduction diffusion is the method by which most of the 500 to 600 t of the magnetic samarium-cobalt alloy (SmCOs) are produced every year. 

This chapter addresses how silicon cell models can be used in biosimulation for systems biology. We first describe the process of model building, as well as its purpose and how it fits in systems biology. Then we compare the use of silicon cell models with the use of the less-detailed core models. We briefly discuss various simulation methods used to model phenomena involving diffusion and/or stochas-ticity as well as methods for model analysis. Finally we discuss balanced truncation as a method for model reduction. This method is illustrated by applying it to a silicon cell model of yeast glycolysis. 

Reduction of the vapor transmittance of latex films as a result of vibrowave influences on the latex, measured by diffusion method, also confirms the change of a film structure under the influence of nonlinear vibrations [8], It is necessary to emphasize, that the influence of vibrowave treatment observed already at a stage of synthesis of polymers [14] is efficient at the subsequent stages of formation of a complex of properties of polymeric composite materials. 

The second method involves the so-called calciothermic reduction of rare earth oxides by means of calcium in the presence of 3d metals under a protective atmosphere (Cech 1974, Herget and Domazer 1975, Sun Guangfei et al. 1985, Herget 1987, Zhou et al. 1987). This process is commonly referred to as the reduction-diffusion (R-D) process. Basically, it involves two steps. In the first step, performed at 900-1100 °C, the actual reduction of Nd203 takes place according to the reactions ... 

In the reduction/diffusion version of the method, first developed by General Electric in the USA (Cech 1974), all the cobalt and any other TM is introduced as a fine metallic powder, blended with calcium granules, and the mixture reacted under a hydrogen atmosphere. The reaction according to the equation... 

The improved antibacterial activity of the BC-chitosan composite via the impregnation approach was reported. Firstly, the antimicrobial evaluation was performed by the direct contact of the composite with coli and S. aureus. The growth reductions of 99.9% were observed in both cultures. Secondly, the evaluation was performed by the disc diffusion method. Because of a tight incorporation between chitosan and BC, it resulted in no chitosan diffusion out of the composite. Therefore, no inhibitory clear zone was found [20],... 

Chemical-deposition Electrode. Chemical techniques can also be employed in the fabrication of catalyst layers by platinizing the surface of a Nafion membrane. One approach [65, 66] is to expose one side of the Nafion membrane to a reductant solution (e.g., hydrazine solution) and the other side to a platinic acid solution. The reductant diffuses across the membrane to react with platinic acid and form a Pt catalyst layer. In another impregnation-reduction method [3, 67, 68] a cationic salt, such as Pt(NH3)4Cl2, is first impregnated into the Nafion membrane, followed by exposing this membrane to a reductant, such as NaBUj. As shown in Figure 19.13, a dense and porous platinum film can be formed using this chemical deposition technique. 

Since the R-Co alloys have become technically significant, many efforts have been made to lower the cost of the R-Co alloys which are the starting materials for the magnet production. In the last three years new methods have been developed, which avoid the preparation of pure R metals which are later melted with Co and other transition metals, but start with rare earth oxides (R20a) and Co oxide. These processes are known under the names reduction-diffusion process and co-reduction process . 

Unlike other global methods for spectral dimensionality reduction. Diffusion Maps does not compute a -nearest neighbour graph. Rather, the affinities are computed for each pairing of data points, that is, the affinities (Eq.2.6) are calculated for all points such that the affinity matrix W is dense. Since the affinities are calculated for all n points, the cost of computing the affinity matrix is 0 rp-). This computational... 

Electrochemical reduction of iridium solutions in the presence azodye (acid chrome dark blue [ACDB]) on slowly dropping mercury electrode is accompanied by occurrence of additional peaks on background acetic-ammonium buffer solutions except for waves of reduction azodye. Potentials of these peaks are displaced to cathode region of the potential compared to the respective peaks of reduction of the azodye. The nature of reduction current in iridium solutions in the presence ACDB is diffusive with considerable adsorptive limitations. The method of voltamiuetric determination of iridium with ACDB has been developed (C 1-2 x 10 mol/L). 

The comparison with experiment can be made at several levels. The first, and most common, is in the comparison of derived quantities that are not directly measurable, for example, a set of average crystal coordinates or a diffusion constant. A comparison at this level is convenient in that the quantities involved describe directly the structure and dynamics of the system. However, the obtainment of these quantities, from experiment and/or simulation, may require approximation and model-dependent data analysis. For example, to obtain experimentally a set of average crystallographic coordinates, a physical model to interpret an electron density map must be imposed. To avoid these problems the comparison can be made at the level of the measured quantities themselves, such as diffraction intensities or dynamic structure factors. A comparison at this level still involves some approximation. For example, background corrections have to made in the experimental data reduction. However, fewer approximations are necessary for the structure and dynamics of the sample itself, and comparison with experiment is normally more direct. This approach requires a little more work on the part of the computer simulation team, because methods for calculating experimental intensities from simulation configurations must be developed. The comparisons made here are of experimentally measurable quantities. 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

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