Reversible phase transformation in the Pd2Si-PdSi thin-film system

The thermal stability of thin PdSi films has been studied at temperatures ranging between 300 and 700 °C. The PdSi, when in contact with crystalline Si, transforms into Pd2Si and Si at temperatures of 500–700 °C, a process contrary to the equilibrium-phase diagram. The rate of transformation was found to depend on the structure and orientation of the Si. Upon heating above 750 °C, Pd2Si transforms back to PdSi. However, PdSi is stable against annealing when in contact with Pd2Si or an inert substrate SiO2. We propose that the decomposition of PdSi into Pd2Si and Si in the presence of crystalline Si is due to a lower interface energy of the Pd2Si-Si interface compared to that of the PdSi-Si interface

The Baillon–Simons theorems

AbstractIn this paper, we give combinatorial proofs of Baillon and Simons’ almost fixed point and fixed point theorems for discrete-valued mappings (J. Combin. Theory Ser. A 60 (1992) 147–154)

Influence of atomic mixing and preferential sputtering on depth profiles and interfaces

Atomic mixing and preferential sputtering impose a depth resolution limit on the use of sputter sectioning to measure the composition of metal–semiconductor interfaces. Experimental evidence obtained with the Pt–Si system is used to demonstrate ion‐induced atomic mixing and then its effect on sputter etching and depth profiling. Starting with discrete layer structures, a relatively low ion dose (≳3×10^(15) cm^(−2)) first produced a mixed surface layer with thickness comparable to the ion range. Higher ion doses then result in successive sputter etching and continual atomic mixing over a constant surface layer thickness. A model is developed that is based on a sputter removal (including preferential sputtering) of atoms at the surface and a uniform mixing of atoms over a constant thickness. The model predicts the influences of atomic mixing and preferential sputtering on the depth profiling of thin‐film structures and interfaces

A Study of Polymer/Surfactant Interactions for Micellar/Polymer Flooding Applications

Static measurements of the phase volumes of mixtures of surfactant, polymer, alcohol, water, n-octane, sodium chloride, and in some cases polymer additives were made. A limited number of viscosity, phase concentration, and IFT measurements were also made. The purpose was to systematically determine the affect of various polymers on the phase behavior of various surfactant formula-tions. Measurements with and without oil (n-octane) were made across a range of salinity appropriate to the particular surfactant at temperatures between 24 and 75° C. The polymers used were xanthan gum, hydrolyzed polyacrylamide, polyacrylamide, hydroxyethylcellulose, and polyethyleneoxide of three different molecular weights. The surfactants used were Exxon's C 12 MEAOXS, Witco's TRS 10-80, Stepan's Petrostep 465, Alcolac's Siponate DS-10, GAF's Igepal C0-530 and C0-610, and Witco's ethoxylated alcohol TDA-100. The alcohols were isobutyl, secondary butyl, isopentanol, and isopropanol. The oil free (i.e. no added oil) solutions showed a characteristic phase seperation into an aqueous surfactant rich phase and an aqueous polymer rich phase, at some sufficiently high salinity (NaCl concentration), which we call the CEC. The CEC was found to be a characteristic 6f a given surfactant/alcohol combination, which shifts with the solubility of the surfactant, qualitatively the ., same way as the optimal salinity does. But the CEC was found to be independent of the polymer type, polymer concentration (between the 100 and 1000 ppm limits investigated), and surfactant concentration. The CEC increases with temperature for the anionic surfactants and decreases with temperature for the nonionic surfactants. When oil was added to the above mixtures an entirely different pattern of phase behavior was observed. The particular formulations form the typical sequence of lower phase microemulsion and excess oil; middle phase microemulsion, excess oil, and excess brine; and upper phase microemulsions and excess brine; as salinity increases. The sequence with polymer was precisely the same over most of the salinity range but deviated over a limited range of salinity: the three phase region simply shifts a small distance to the left on the salinity scale. Also, and probably more significantly, some of the "aqueous" phases in the critical region of the shift (which is also just above oil-free CEC salinity) were found to be gel-like in nature. These apparently occur under conditions such that the polymer concentration in the excess brine of the three phase systems becomes very high, due to the fact that almost all the polymer is always in the brine phase, even when the brine phase is very small. Thus an overall 1000 ppm of polymer can easily be concentrated to 10000 ppm or more. One of the most remarkable aspects of the phase behavior of the surfactant/polymer systems is that the same patterns are observed for all combinations of anionic and nonionic surfactants and polymers. Also, little difference was observed in the IFT values with and without polymer. The three phase systems still exhibited ultra-low IFT values. Obviously, significant differences did occur in the brine viscosities when polymer was added. The polymer free mixtures were themselves quite viscous, however; and the viscosity of the oil free surfactant rich phases (above the CEC) were significantly higher when in equilibrium with a polymer rich aqueous phase, even though apparently containing almost no polymer. The polymer rich phases had normal viscosities as judged by the same polymer in the same brine at the expected concentration assuming all of the polymer was in the polymer rich phase. The affect of polymer on the systems with oil was to increase the viscosity of the water rich phase only, with little effect on the microemulsion phase unless it was the water rich phase.Petroleum and Geosystems Engineerin

An analysis of the dense packing of disks : a computer simulated approach

This thesis is concerned with the analysis of dense packing of hard disks. The Voronoi diagram and the geometric neighbours were first computed. The average number of geometric neighbours of a disk is six. It is thus more efficient to choose structural neighbours from among the geometric neighbours than from among all other disks. Through the Monte Carlo simulation by Rosato et. al., disk configurations after pouring and subsequent shaking were provided for analysis. The mean number of geometric neighbours and the average coordination number were computed. The angular distribution of the structural neighbours was discussed. The packing fraction increases with number of shakes in a linear relationship. It seems to be packing into an ordered close packing after continued shaking. A configuration constrained by two rigid vertical walls was analyzed. It was found the packing fraction is smallest in the vicinity of the wall and increased asymptotically to the mean packing fraction when moving away from the wall

Sequence of phase formation in planar metal-Si reaction couples

A correlation is found between the sequence of phase formation in thin-film metal-Si interactions and the bulk equilibrium phase diagram. After formation of the first silicide phase, which generally follows the rule proposed by Walser and Bené, the next phase formed at the interface between the first phase and the remaining element (Si or metal) is the nearest congruently melting compound richer in the unreacted element. If the compounds between the first phase and the remaining element are all noncongruently melting compounds (such as peritectic or peritectoid phases), the next phase formed is that with the smallest temperature difference between the liquidus curve and the peritectic (or peritectoid) point

Tourism demand forecasting using a novel high-precision fuzzy time series model

[[abstract]]Fuzzy time series model has been developed to either improve forecasting accuracy or reduce computation time, whereas a residul analysis in order to improve its forecasting performance is still lack of consideration. In this paper, we propose a novel Fourier method to revise the analysis of residual terms, and then we illustrate it to forecast the Japanese tourists visiting in Taiwan per year. The forecasting results show that our proposed method can derive the best forecasting performance as well as the smallest forecasting error of MAPE in the training sets; in the testing sets, the proposed model is also better to fit the future trend than some forecasting models.[[incitationindex]]EI[[booktype]]電子版[[booktype]]紙

Depth dependence of atomic mixing by ion beams

Ion backscattering spectrometry has been used to investigate the depth dependence of atomic mixing induced by ion beams. Samples consisting of a thin Pt (or Si) marker a few tens of angstroms thick buried at different depths in a deposited Si (or Pt) layer were bombarded with Xe+ of 300 keV at 2×10^16 cm^–2 dose and Ar+ of 150 keV at 5×10^15cm^–2 dose. Significant spreading of the marker was observed as a result of ion irradiation. The amount of spreading was measured as a function of depth of the marker, which was then compared with the deposited energy distribution. Measurements of this kind promise new insight into the nature of the interaction between ion beams and solids

Green Performance Assessment for Retail Industry in Taiwan

[[abstract]]The retail industry in Taiwan plays an important role in people's lives and influences consumers' purchasing behavior. Due to global warming and the depletion of energy and other resources, most retailers are required to obey the green policy of reuse, recycling, and reduction in their operational process, service, and products. Therefore, we first evaluated the environmental performance of retailers using selected green criteria. Then, we assessed the performance of sustainable environmental practices among ten selected retailers using grey relation analysis and the entropy method to derive objective weights for the selected criteria. Next, for continuous improvement of retailers' green performance, we extracted and summarized a self-assessment checklist selected from the questionnaire. Retailers can use the checklist for guidelines for continuous improvement.[[notice]]補正完

Fuzzy Portfolio Model with Application to Business Cycles Analysis

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