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971.
A simple method has been developed to optimally design a distillation sequence with a fixed degree of flexibility in feed composition and flowrate, and accounts for uncertainty in stage efficiency, K-value and beat transfer coefficient calculations. The method minimizes a weighted cost function and ensures both optimal and feasible operation in the range of flexibility/uncertainty by using an approach termed “practical feasibility”. The method was tested on a 4 column distillation sequence separating a 5 component light alkane feed mixture. Results are presented to illustrate the effect of uncertainty on sequence cost and column overdesign. 相似文献
972.
973.
Multiwalled carbon nanotubes (MWCNT) were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and by adsorption of N2 and acetylene. The dynamics of acetylene sorption was studied by frequency response spectroscopy. The average tube dimension and the shell number were determined from a statistical evaluation of the TEM images. This value agreed with that obtained from XRD via the Scherrer equation only if a shape factor of 0.49 was used. The diffusion of acetylene in the nanotubes of the MWCNT sample was found to be the rate-controlling step of the sorption process. Relationships between the tube dimensions and the equilibrium and dynamic sorption properties were demonstrated. 相似文献
974.
Field survey of the geometrical isomers of 7,9-dodecadienyl alcohol, acetate, and aldehyde has resulted in attractants and inhibitors for three species of tortricid moths.Epinotia silvertoniensis and an undescribedEpinotia sp. were all attracted to (Z,Z)-7,9-dodecadienyl acetate. AnotherEpinotia sp. was attracted to (Z,Z)-7,9-dodecadienyl acetate and (Z,Z)-7,9-dodecadien-1-ol. Electroantennogram data and inhibition patterns for one of theEpinotia sp. are also reported. In addition,E. criddleana was attracted to lures containing (E)-9-dodecenyl acetate. 相似文献
975.
Carbon-encapsulated Fe nanoparticles with size between 5 and 20 nm were synthesized via a picric acid-detonation-induced pyrolysis of ferrocene, which is characterized by a self-heating and extremely fast process. The nanoparticles exhibit well-constructed core-shell structures, with bcc-Fe cores and graphitic shells. The graphitic shells can protect effectively the cores against the attack of HNO3 solution. The formation of the core-shell nanoparticles can be selectively controlled by adjusting the composition of the picric acid-ferrocene mixture, which determines C/Fe atomic ratio of the reaction system. The core-shell nanoparticles are preferably formed at low C/Fe atomic ratios, while tubular structures are formed at high C/Fe ratio. The possible pathway for the carbon-encapsulated Fe nanoparticles formation is discussed briefly. 相似文献
976.
The present investigation describes the quantitative measurement of surface functional groups present on commercially available different PAN based carbon fibers, their effect on the development of interface with resol-type phenol formaldehyde resin matrix and its effect on the physico-mechanical properties of carbon-carbon composites at various stages of heat treatment. An ESCA study of the carbon fibers has revealed that high strength (ST-3) carbon fibers possess almost 10% reactive functional groups as compared to 5.5 and 4.5% in case of intermediate modulus (IM-500) and high modulus (HM-45) carbon fibers, respectively. As a result, ST-3 carbon fibers are in a position to make strong interactions with phenolic resin matrix and HM-45 carbon fibers make weak interactions, while IM-500 carbon fibers make intermediate interactions. This observation is also confirmed from the pyrolysis data (volume shrinkage) of the composites. Bulk density and kerosene density more or less increase in all the composites with heat treatment up to 2600 °C. It is further observed that bulk density is minimum and kerosene density is maximum upon heat treatment at 2600 °C in case of ST-3 based composites compared to HM-45 and IM-500 composites. It has been found for the first time that the deflection temperature (temperature at which the properties of the material start to decrease or increase) of flexural strength as well as interlaminar shear strength is different for the three composites (A, B and C) and is determined by the severity of interactions established at the polymer stage. Above this temperature, flexural strength and interlaminar shear strength increase in all the composites up to 2600 °C. The maximum value of flexural strength at 2600 °C is obtained for HM-45 composites and that of ILSS for ST-3 composites. 相似文献
977.
978.
During the preparation of alumina as a catalyst support from aluminium nitrates by precipitation with a NH4OH base, NO
2
⋅
radicals have been formed in the catalyst after calcination under air in the solid at different temperatures. These radicals
remained stable until a calcination temperature of 800°C. When the calcined catalyst was degassed under vacuum above 300 °C,
the NO
2
⋅
was reduced to give NO⋅ and O- species which were both tightly trapped in the solid. These latter species remained stable until vacuum treatment at 800
°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
979.
980.
Infra-red measurements of the dichroic ratio of atactic polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide) absorption bands provide a valuable method for the determination of orientation as well as relaxation of chains of both polymers during stretching of their compatible blends. Influence of strain rate, temperature of stretching, and molecular weight of the polymers on orientation of both polymer chains in blends containing up to 35% PPO has been studied. Orientation relaxation for both polymers has been analysed using Lodge's constitutive equation. Master curves have been obtained for PPO and PS in the blends at a reference temperature T0 = Tg + 10°C. Results are interpreted in terms of an hindrance of relaxation of PS chains induced by interaction with a highly-oriented PPO network which slowly relaxes. 相似文献