排序方式: 共有28条查询结果,搜索用时 250 毫秒
1.
2.
3.
Experimental work on post-breakdown bulk oscillations in n-type gold-doped phosphorus-compensated p+?i?n+ double-injection diodes is presented. An empirical relationship for the frequency of oscillation in this region is derived for the first time and discussed. 相似文献
4.
The present investigation analyses the thermodynamic behaviour of the surfaces and adsorption as a function of temperature and composition in the Fe-S-O melts based on the Butler's equations. The calculated values of the surface tensions exhibit an elevation or depression depending on the type of the added solute at a concentration which coincides with that already present in the system. Generally, the desorption of the solutes as a function of temperature results in an initial increase followed by a decrease in the values of the surface tension. The observations are analyzed based on the surface interaction parameters which are derived in the present research. 相似文献
5.
Integral excess free energy of a quaternary system has been expressed in terms of the MacLaurin infinite series. The series is subjected to appropriate boundary conditions and each of the derivatives correlated to the corresponding interaction coefficients. The derivation of the partial functions involves extensive summation of various infinite series pertaining to the first order and quaternary parameters to remove any truncational error. The thermodynamic consistency of the derived partials has been established based on the Gibbs-Duhem relations. The equations are used to interpret the thermodynamic properties of the Fe-Cr-Ni-N system. 相似文献
6.
A thermodynamic model based on the thermodynamic principles is developed to predict the eutectic temperature and composition
in molten salt systems. The LiNO3-NaNO3-KNO3 ternary system was chosen to demonstrate the applicability of this model. The calculated eutectic composition and temperature
obtained from the thermodynamic model were verified experimentally using the Differential Scanning Calorimeter (DSC) technique.
The experimentally determined melting temperature of the eutectic composition was in excellent agreement with that of calculated
eutectic temperature of the system. The results obtained from this study suggest that this thermodynamic model can be successfully
extended to predict the eutectic points in other molten salt systems. 相似文献
7.
Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s(-1)). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731-6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing. 相似文献
8.
M. Ramachandran D. Mantha C. Williams R. G. Reddy 《Metallurgical and Materials Transactions A》2011,42(1):202-210
The oxidation resistance of Ti-Al intermetallics is superior to many of their counterparts at high temperatures. High-temperature
stability of these intermetallics appears to improve with a ternary alloying addition such as Mo, Nb, etc. A detailed analysis of oxidation of the Ti3Al intermetallics, Ti3Al-2.9 at. pct Mo and Ti3Al-1.1 at. pct Nb, in pure oxygen using crystallographic and microscopic techniques is presented here. The alloy containing
1.1 at. pct Nb did not show an improvement in oxidation resistance over the base alloy but that containing 2.9 at. pct Mo
showed marked resistance to oxidation. Activation energies of oxidation for both the alloys were comparable with those reported
in the literature for similar compositions. TiO2 and Al2O3 were the major phases present in the oxide scales of the oxidized alloys. The crystal orientations from the X-ray diffraction
(XRD) patterns and the morphologies from scanning electron microscopy (SEM) were in good agreement and were helpful in further
analysis of the oxidation process. The effective diffusion of oxygen in the oxide layers was calculated using the mole fraction
of individual oxide and the diffusivity of oxygen in pure oxide. The activation energy for the effective diffusion of oxygen
through the oxide layers was determined to be ~24 kJ/mol. The activation energy for the oxidation process was higher than
that of the diffusion of oxygen. Hence, it can be concluded that the oxidation process in both the alloys studied is not diffusion
controlled. 相似文献
9.
The present investigation calculates the surface tension and adsorption functions of the Fe-O and Fe-O-N melts at 1823 K using
the modified form of Butler’s equations and the derived values of the surface interaction parameters of the systems. The calculated
values are found to be in good agreement with those of the experimental data of the systems. The present analysis indicates
a characteristic saturation behavior of oxygen in the Fe-O system at 1823 K, whereas a linear adsorption behavior is observed
in the Fe-N system. An inverse relationship in the adsorption behavior, which exists between oxygen and nitrogen in the Fe-O-N
system, is similar to that observed in our earlier study of the Fe-S-N system. 相似文献
10.
Nitrobenzene is a major environmental pollutant, and its degradation is difficultto achieve. Hence, a chemical reduction pretreatment is sought in this research, before the resulting aniline can be treated by enzyme-mediated oxidative polymerization. Zerovalent iron (Fe0) has been successfully employed to reduce nitrobenzene to aniline in synthetic wastewater in both batch and continuous flow reactors. The concentration of nitrobenzene studied was thatwhich would be present in industrial wastewater streams (millimolar, 123 ppm), a concentration range considerably higher than those studied previously with groundwater by other researchers. Anaerobic conditions were maintained in the reactors by including Na2SO3 as an oxygen scavenger in the presence of CoCl2.6H2O, which acted as a catalyst. Batch reactors exhibited adsorption of aniline on the Fe0, which could be described by a langmuir isotherm. A 200 g Fe0 (particle size: 1-2 mm) bed completely converted 1 mM of nitrobenzene flowing upward for about 600 pore-volumes before experiencing flow reduction due to clogging due to corrosion products. Green-black precipitates (Fe0 corrosion products) were formed at the influent end of the column which were identified as maghemite. 相似文献