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An improved portable odor sampling system (OSS) of the wind tunnel type was designed to determine odor emissions from areal sources. The aerodynamics of the odor emission hood was observed using a number of smoke tests and dry ice tests. The velocity profiles were also measured horizontally and vertically in the hood by an anemometer. Modifications in the form of an extension inlet duct, flat vanes, and a baffle were necessary to achieve repeatable, uniform, and steady velocity profiles inside the hood. The optimum velocity for use of the OSS was found to be 0.33 m/s, based upon the aerodynamic performance of the OSS and the sensitivity of the anemometer at a lower velocity.

Using ab initio calculations, we have evaluated two structural descriptions of γ-Al(2)O(3), spinel and tetragonal hausmannite, and explored the relative stability of γ-Al(2)O(3) with respect to α-Al(2)O(3) with 2.5 at.% of Si, Cr, Ti, Sc, and Y additives to identify alloying element induced electronic structure changes that impede the γ to α transition. The total energy calculations indicate that Si stabilizes γ-Al(2)O(3), while Cr stabilizes α-Al(2)O(3). As Si is added, a bond length increase in α-Al(2)O(3) is observed, while strong and short Si-O bonds are formed in γ-Al(2)O(3), consequently stabilizing this phase. On the other hand, Cr additions induce a smaller bond length increase in α-Al(2)O(3) than in γ-Al(2)O(3), therefore stabilizing the α-phase. The bulk moduli of γ-Al(2)O(3) with these additives show no significant changes. The phase stability and elastic property data discussed here underline the application potential of Si alloyed γ-Al(2)O(3) for applications at elevated temperatures. Furthermore it is evident that the tetragonal hausmannite structure is a suitable description for γ-Al(2)O(3).

Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O 2 -N 2 atmosphere. It is shown that the presence of N 2 allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O 2 partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O − ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O − ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O − ion flux without N 2 addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO 2 is independent from the O − bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO 2 crystal structure at the expense of the monoclinic HfO 2 one.

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