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排序方式: 共有190条查询结果,搜索用时 15 毫秒
71.
Kiran K. Sathyanarayanarao Subbarao Camilo C. M. Rindt Anton A. van Steenhoven 《传热工程》2013,34(8-9):733-743
The flue gases emanating from the combustion of fuels or gasification process invariably comprise particulate matter and many chemical species in vapor form. The temperature of the flue gases gradually reduces when passing through different sections of heat exchanger, such as the superheater, evaporator, and so on. If the temperatures of the heat exchanger tube surface and the gas phase are favorable for condensation, the chemical species in the vapor form will condense on the particles and on the tube surface. The particle deposition behavior under these conditions is drastically different from the one observed in dry particulate fouling. In order to model the particle deposition under such circumstances, it is important to evaluate the criteria for particle adhesion to the surface. Impaction experiments of particles impacting a surface coated with a thin liquid film and particles that are coated with a liquid film impacting over a dry surface are performed to evaluate the limiting parameters under which a particle sticks to the surface without rebounding. The effects of liquid viscosity, liquid film thickness, and interacting material properties are evaluated. The experimental results are compared to the results of existing models and a suitable model for fouling is proposed. Controlled fouling experiments are performed for varying liquid films coated over a deposition tube under various process conditions to mimic the condensation effects on fouling. The results are compared with detailed impaction experiments. 相似文献
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75.
H Jin K Subbarao S Bagai GP Leser BR Murphy RA Lamb 《Canadian Metallurgical Quarterly》1996,70(3):1406-1414
The C terminus of the influenza virus hemagglutinin (HA) contains three cysteine residues that are highly conserved among HA subtypes, two in the cytoplasmic tail and one in the transmembrane domain. All of these C-terminal cysteine residues are modified by the covalent addition of palmitic acid through a thio-ether linkage. To investigate the role of HA palmitylation in virus assembly, we used reverse genetics technique to introduce substitutions and deletions that affected the three conserved cysteine residues into the H3 subtype HA. The rescued viruses contained the HA of subtype H3 (A/Udorn/72) in a subtype H1 helper virus (A/WSN/33) background. Rescued viruses which do not contain a site for palmitylation (by residue substitution or substitution combined with deletion of the cytoplasmic tail) were obtained. Rescued virions had a normal polypeptide composition. Analysis of the kinetics of HA low-pH-induced fusion of the mutants showed no major change from that of virus with wild-type (wt) HA. The PFU/HA ratio of the rescued viruses grown in eggs ranged from that of virus with wt HA to 16-fold lower levels, whereas the PFU/HA ratio of the rescued viruses grown in MDCK cells varied only 2-fold from that of virus with wt HA. However, except for one rescued mutant virus (CAC), the mutant viruses were attenuated in mice, as indicated by a > or = 400-fold increase in the 50% lethal dose. Interestingly, except for one mutant virus (CAC), all of the rescued mutant viruses were restricted for replication in the upper respiratory tract but much less restricted in the lungs. Thus, the HA cytoplasmic tail may play a very important role in the generation of virus that can replicate in multiple cell types. 相似文献
76.
E C Subbarao 《Bulletin of Materials Science》1994,17(6):883-891
Ferroelectrics undergo one or more crystallographic phase transitions, which involve lattice distortions. The direction of
spontaneous polarization in ferroelectrics can be reoriented by an applied electric field (or mechanical stress). There is
a spontaneous strain accompanying spontaneous polarization. Phase transitions and domain reorientations thus result in microdeformations.
Many devices such as actuators and transducers are based on this behaviour. The origin of microdeformations in ferroelectrics
and their consequences are discussed here. 相似文献
77.
Two studies examined the role of characteristics that are important to consider in the development of computerized training systems. The first study employed covariance structure modeling and tested a hypothesized model regarding the relationship among three latent variables and a set of measured variables serving as indicators for the latent variables. The overall model fit quite well according to both statistical and practical assessments. Results indicate that, for naive users, a latent variable reflecting an individual's attitude toward computers has a significant influence on the other two latent variables, one being how the computerized task is perceived, and the second being the choice of interacting with a computer in the future. A structural path representing the influence of the current experience with the computer has a small directional influence on future interaction preference with a person rather than a computer. A second study examined system characteristics and focused specifically on preferences for how much power an expert system should be given. Scenarios were developed depicting three different types of expert systems, each with three different levels of power. Results indicate that individuals prefer those systems with either low or moderate power, those which do not initiate action without human intervention. Systems that initiate action on their own are not viewed positively. The discussion focuses on implications for future training systems. 相似文献
78.
The Internet has been growing tremendously in the recent years and applications like web browsing are becoming increasingly popular. In a collective effort to provide seamless access to the Internet, wireless equipment manufacturers and service providers are developing 3G wireless systems that efficiently support current and future Internet applications. In this paper, we evaluate the performance and capacity of a 3G wireless data system based on IS-2000 standard. We consider web browsing as the common application for all users and evaluate the system performance for single and parallel web browsing sessions. We perform this study through a detailed simulation of web traffic model described by distributions of number of objects per page, object size, page request size and page reading time. The simulation includes HTTP and TCP/IP protocols, link level recovery, radio resource management, mobility, channel model and, delays in the Internet and the radio access network. We quantify important system attributes like average page download times and system throughput (Kb/s per carrier per sector). We also evaluate normalized object download time, normalized page download time, penalty in performance due to link errors, link layer buffer sizes needed, channel holding time, average power used and distribution of the power used in the system. 相似文献
79.
Hydrogenation of unsaturated fatty acid methyl esters with diimide from hydroxylamine-ethyl acetate 总被引:1,自引:0,他引:1
A. Gangadhar T. Chandrasekhara Rao R. Subbarao G. Lakshminarayana 《Journal of the American Oil Chemists' Society》1989,66(10):1507-1508
Methyl esters of 10-undecenoic, oleic, linoleic and castor oil fatty acids were hydrogenated with hydroxylamine-ethyl acetate
reagent under nitrogen, without change in position and configuration of double bonds. The fatty acid ester was also found
to participate in the generation of diimide. No hydrazide was formed. 相似文献
80.
P. Vijayalakshmi R. Subbarao G. Lakshminarayana 《Journal of the American Oil Chemists' Society》1991,68(2):133-137
Cycloaliphatic C21 di- and C22 tricarboxylic acids were prepared by the Diels-Alder reaction of dehydrated castor oil (DCO) fatty acids (containing 48%
conjugated and 42% nonconjugated dienes) with acrylic and fumaric acids, respectively. The reaction temperature, time, catalyst
concentration, and mole ratio of reactants were varied to get maximum yields of the di- and tricarboxylic acids. The unreacted
DCO fatty acids were removed from the products by partition between aqueous methanol and n-hexane. The products were converted
to methyl esters and characterized as the substituted cyclohexene derivatives before and after dehydrogenation with Pd/C in
xylene, hydrogenation with Pd/C in decalin and oxidation with periodate-permanganate reagent and by mass and proton nuclear
magnetic resonance spectrometry. The acids were converted to sodium soaps, mono- and diethanolamides and the corresponding
diol and triol sulfates, and the resulting products were evaluated for their surface-active properties. The sodium soaps showed
better calcium tolerance and poorer foaming power than sodium oleate. The diethanolamides were inferior to lauroyl diethanolamide
in wetting and emulsifying power. The monoethanolamides were better than the respective diethanolamides and lauroyl diethanolamide
in wetting property. The diol and triol sulfates were poorer in wetting and emulsifying ability and better in calcium tolerance
than sodium lauryl sulfate. 相似文献