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Segregation Processes (segregation + process)
Selected AbstractsAnalysis of segregation process of n -alkanes in binary mixtures by FTIR and Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2005Andrzej Hacura Abstract In the FTIR and Raman spectroscopic studies, the phenomena of normal n -alkanes segregation in the binary mixtures of solid-state paraffin at room temperature were examined. Samples, in which one of the ingredients had been deuterated were prepared in different molar concentrations. Components of the mixture separated in time, creating separate domains, were observed in the changing of shape of infrared and Raman bands. The process of segregation depended on the difference of the chains' length of the mixture's ingredients and the molar fraction, in which the mixtures were prepared. The size of the created microdomains has been estimated based on the model describing shape and the splitting of the IR bands developed by Hiebert and Hornig. By applying the micro-Raman imaging technique, a number of surface maps have been obtained indicating the separating process of ingredients of the mixtures. This allowed comparing and verifying time dependent results of the IR study. Copyright © 2005 John Wiley & Sons, Ltd. [source] HgTe segregation process in HgCdTe studied by E1 reflectance peak positionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006M. Pociask Abstract Long term diffusion processes near the Cd1,xHgxTe surface influences the electronic structure as is shown in this paper. Measurements of reflectivity and surface characterisation by means of scanning electron microscopy (SEM) were performed for samples with x = 0.4 and x = 0.62. The optical results were compared with the reflectivity spectra obtained 22 years ago using the same samples. We discuss the observed dramatic changes in the optical changes upon the SEM and comparative analysis. E1 + , reflectance peak position corresponds to binary HgTe in both recently investigated samples. That method reflection is sensitive to no more than 120 µm the upper depth of investigated samples. The measurements of the E1 reflectance peak has proven to be a helpful and convenient tool for mercury telluride segregation near the HgCdTe surface and may be used to determine composition and age of HgCdTe. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Residential Segregation Influences on the Likelihood of Ethnic Self-EmploymentENTREPRENEURSHIP THEORY AND PRACTICE, Issue 2 2009Gregory B. Fairchild Geographic and environmental influences on economic action have a long history in managerial research. This paper develops and estimates a model of the potential of a broad set of U.S. racial minority groups to enter self-employment based on individual-level, household-level, and metropolitan area-level factors. The model allows for an analysis of two distinct residential segregation processes on self-employment likelihood. Results indicate that clustering by race has group-specific influences, increasing the likelihood of self-employment for some groups and diminishing for others. Higher levels of racial exposure raise the likelihood of entrepreneurial careers for all groups, but especially for Blacks. [source] Granular mixing and segregation in a horizontal rotating drum: A simulation study on the impact of rotational speed and fill levelAICHE JOURNAL, Issue 12 2008M. M. H. D. Arntz Abstract The rich phase behavior of granular beds of bidisperse hard spherical particles in a rotating horizontal drum is studied by Discrete Element Method (DEM) simulations. Several flow regimes and various forms of radial segregation, as well as mixing, are observed by systematically varying the operational parameters of the drum, i.e. fill level and angular velocity, over a wide range. Steady states after several dozen revolutions are summarized in two bed behavior diagrams, showing strong correlations between flow regime and segregation pattern. An entropy method quantifies the overall degree of mixing, while density and velocity plots are used to analyze the local properties of the granular bed. The percolation mechanism may provide a qualitative explanation for the distinct segregation processes, and for the transient mixing in nonradially segregated beds. Initially blockwise segregated beds are found to mix before radial segregation sets in. High fill fractions (>65%) show the most intense segregation. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Kinetics of coupled ordering and segregation in antiphase domainsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009K. Gumennyk Abstract We study a multi-domain ordering kinetics in solid solutions under simultaneous diffusion of solute atoms. By the example of a binary bcc alloy a system of kinetic equations is derived, describing the coupled relaxation of occupancies of the two sublattices, building a bcc lattice, by A and B atomic species. Such an approach supplemented by the simplest mean-field approximation proves sufficient to describe both the establishing of long-range order and the segregation processes occurring in antiphase domains. An interaction and interrelation between evolution of the conserved and non-conserved order parameter fields are elucidated. Asymptotical and numerical analysis of the obtained evolution equations reveals a multi-stage scenario of the alloy relaxation: first comes the quick development of long-range order which is then followed by the slow redistribution of local alloy concentration, so that the majority atoms segregate towards the region of an antiphase boundary. The alloy exhibits a distinct tendency to form a multi-domain structure out of a solitary long-range order parameter fluctuation of a certain sign. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Assessment of the plasma desorption time-of-flight mass spectrometry technique for pesticide adsorption and degradation on ,as-received' treated soil samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2005J. P. Thomas The assessment of the plasma desorption time-of-flight mass spectrometry (PD-TOFMS) technique as a tool for direct characterization of pesticides adsorbed on agricultural soil is made for the first time in this study. Pellets of soils impregnated by solutions of three pesticides, namely norflurazon, malathion and oxyfluorfen, as well as deposits of these solutions onto aluminum surfaces, were investigated to this end. The yield values of the most characteristic peaks of the negative ion mass spectra were used to determine both the lowest concentrations detected on soils and limits of detection from thin films. The lowest values on soils are for malathion (1000,ppm range), and the largest for norflurazon (20,000,ppm), which is close to the limit of detection (LOD) found for the pesticide on the aluminum substrate (,0.2,µg,·,cm,2). Different behaviors were observed as a function of time of storage in the ambient atmosphere or under vacuum; norflurazon adsorbed on soil exhibited high stability for a long period of time, and a rapid degradation of malathion with the elapsed time was clearly observed. The behavior of oxyfluorfen was also investigated but segregation processes seem to occur after several days. Although by far less sensitive than conventional methods based on extraction processes and used for real-world analytical applications, this technique is well suited to the study of the transformations occurring at the sample surface. A discussion is presented of the future prospects of such experiments in degradation studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||