Alloy 617 (nickel based austenitic alloy) is a candidate structural material for next generation high temperature nuclear reactor. The secondary phases present in the Alloy 617 has been identified as TiN and M23C6 by optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Surface potentials of these phases have been evaluated by Scanning Kelvin Probe Force Microscope (SKPFM). SKPFM investigation showed higher surface potential of the secondary phases than that of the austenite matrix. The surface potential of the TiN was nobler than that of M23C6 indicating that these precipitates could act as cathodic sites during oxidation reaction. Difference in the local chemistry of these phases results in variation of the chemical potentials, which in turn could lead to enhanced oxidation at localized areas in the vicinity of the secondary phase precipitates that act as cathodic sites. 相似文献
L. Plantarum NCIM 2084 cells are homofermentative, essentially producing lactic acid as the main end product of glucose fermentation. Prolonged use through repeated batch fermentation with the cells of L. plantarum immobilized on chitosan treated polypropylene matrix showed a shift in the metabolic pathway from the homofermentative to heterofermentative, accompanied by morphological changes in immobilized cells from the normal rod shape to the coccoid shape. These changes appear to be related to a shift in the bacterial cell metabolism, resulting in a decrease in lactic acid yields. 相似文献
The Laplace-Stieltjes (LS) transform for the distribution of time to first system failure (TFSF), transition probability, availability and mean time to system failure have been derived for two unit repairable redundant standby system with perfect as well as imperfect switchover condition. General expressions for computing various reliability performance indices have been obtained by using Markov Renewal techniques considering general distributions for time to failure and time to repair for the units. 相似文献
Ethyl cellulose embedded prolonged release microparticles containing cimetidine was designed by dispersing the drug-ethyl cellulose mixture in acetone, into a medium of mineral oil and subsequent rigidization of the ethyl cellulose matrix. Significant reproducibility of the manufacturing process was observed. In vitro-in vivo correlation revealed the the dissolution process is the rate determining step in drug absorption and the significant in vivo efficiency of the dosage form is well expected. 相似文献
All epitaxial gold-NaCl/NaBr-gold capacitors were fabricated on hot NaCl substrates. The dielectric properties, capacitance
and loss have been measured. Severe harmonic distortion in the output current has been observed. Maximum contribution was
from third and odd harmonics. The amplitude of harmonics was maximum at frequencies above the loss peak. The phenomenon has
been explained on the basis of nonlinear space charge theories. 相似文献
Polymers are known to undergo order↔order and order↔disorder transitions, when subjected to a change of pressure, temperature, solvent, pH of the medium etc. The molecular processes, which alter the volume of the system, are found to be highly sensitive to the pressure. In the present communication Zimm and Bragg model of helix↔coil transition has been modified to interpret the experimental data of pressure induced phase transition in polystyrene-polybutadiene [PS-PB] at different pressurization rates, as reported by Migler and Han, utilizing the Birefringence and small angle neutron scattering technique. An expression for the degree of order is obtained from the grand partition function for the entire chain in terms of nucleation parameter, which controls the transition width. The nucleation parameter σ increases with the increase in the ODT temperatures of the system. The phenomenon of hysteresis has been discussed in relation to the pressurization rate, which increases/decreases with the corresponding increase/decrease in the pressurization rate. The theoretical transition curves are found to be in good agreement with experimental data. 相似文献
This paper departs from the popular usage of the Backus-Gilbert inversion (BGI) method as a tool for inversion of antenna temperature measurements in microwave radiometry. The BGI method is applied in this paper to enhance the information content of an existing set of oversampled brightness-temperature (TB) data. The purpose is to isolate the inversion process from its resolution enhancement counterpart. The advantage gained is that the resolution enhancement can be performed in a simplified way and in a different level of processing that starts with the scan-mode TB data product and simply requires with it the knowledge of the antenna gain pattern and the sensor's scan geometry. The technique is demonstrated with the 19.35-GHz Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) channel, which provides oversampled TB data. The radiometric resemblance of this channel with that of the 37 GHz and geocollocation of their TB footprints facilitate validation of the enhancement of features. The significance of oversampling the low-frequency (LF) radiometer channels is underscored in the process, which gives the authors the confidence to propose oversampling of the LF data for the forthcoming sensor Microwave Analysis and Detection of Rain and Atmospheric Structures (MADRAS) onboard the Megha_Tropiques mission, which is a joint ISRO-CNES collaboration (due for launch in 2009). 相似文献
The effect of dew point on the selective oxidation behavior, microstructure and mechanical properties of a high-Al low-Si dual phase steel is elucidated. The results showed that as dew point is increased from–30°C to +5°C, internal oxidation of alloying elements occurs, and consequently the mass of external oxides decreases, which improves the galvanisability of steel sheets. It was also observed that the dew point had an impact on the microstructure and mechanical properties of the experimental steel. With the increase of dew point, the decarburization layer on the surface was increased, leading to inferior mechanical properties. Compared with the industrial steel, the high-Al-low-Si DP steel exhibited excellent galvanisability under identical annealing conditions.