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21.
采用等温液相退火和塑性变形工艺制备含不同尺寸Al3Ti和TiB2粒子的Al-5Ti-B(质量分数,%)中间合金。结果表明:随着中间合金中Al3Ti和TiB2粒子尺寸的减小,合金的晶粒细化作用得到增强,但不适当地减小Al3Ti和TiB2的粒径可能导致这些颗粒作用减弱和结块,从而降低合金的晶粒细化效率。  相似文献   
22.
Organic–inorganic hybrid materials consisting of inorganic materials and organic polymers are a new class of materials, which have received much attention in recent years. In the present investigation, at first, the surface of nano-alumina (Al 2 O 3 ) was treated with a silane coupling agent of $\boldsymbol{\gamma} $ -aminopropyltriethoxysilane (KH550), which introduces organic functional groups on the surface of Al 2 O 3 nanoparticles. Then fluorinated polyimide (PI) was synthesized from 4,4 -(hexafluoroisopropylidene) diphthalic anhydride and 4,4 -diaminodiphenylsulfone. Finally, PI/modified Al 2 O 3 nanocomposite films having 3, 5, 7 and 10% of Al 2 O 3 were successfully prepared by an in situ polymerization reaction through thermal imidization. The obtained nanocomposites were characterized by fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The results show that the Al 2 O 3 nanoparticles were dispersed homogeneously in PI matrix. According to thermogravimetry analysis results, the addition of these nanoparticles improved thermal stability of the obtained hybrid materials.  相似文献   
23.
The influence of fermented whey protein concentrate (FWPC) added before and after formation of cheese curd on the textural characteristics of Iranian white cheese was studied. The FWPC, prepared from whey obtained during cheese making, was added at different levels 5, 10, 15 and 20% (v/v) after (A) or before (B) cheese curdling. The changes in rheological parameters of cheeses were determined before and after 1 month of ripening. It was found that both incorporation level and stage of addition of FWPC (A and B) caused significant effects on texture profile analysis of cheeses. Increasing the level of FWPC in B group, except samples containing 10% FWPC, in contrast with A cheeses led to considerable increase in moisture and decrease in hardness and chewiness. Samples containing more than 15% FWPC had undesirable texture and were too soft. All experimental cheeses exhibited a decline in values for each rheological parameter after 1 month of ripening.

PRACTICAL APPLICATIONS


Perhaps the biggest story in the dairy industry in the past couple of decades has been the rise of new applications for whey and whey proteins. Once considered a waste product in the cheese manufacturing process, whey and whey protein products today are used for a wide range of functional and nutritional properties. In the cheese industry, particularly in soft cheese varieties, whey proteins have shown good applications to replace caseins as they act as fat replacer and bind more water than caseins, which results in softer cheeses. Therefore, this study was attempted to investigate the impact of fermented whey protein concentrate on textural attributes of Iranian white cheese.  相似文献   
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The critical path method is the most widely used tool for project management and requires time estimates for duration activities. A linear programming formulation is proposed for determining a critical path (CP). While the proposed approach requires a time estimate for each activity duration, it provides the manager with the allowable simultaneous independent, or dependent changes of the estimates that will preserve the current CP.  相似文献   
26.
A previously developed stochastic two-dimensional network pore structure model has been applied directly to a nickel/alumina commercial catalyst pellet. A technique has been devised to determine the pore diameter distribution function of cylindrical pore segments for any prescribed network dimension which will exactly replicate the experimentally observed mercury penetration curve for the pellet in the method of mercury porosimetry. This stochastic network representation for the catalyst pellet pore structure is superior to the classical parallel bundle model since it incorporates the element of pore interconnectivity. The model has been extended to investigate the phenomena occurring during the accumulation of a foulant deposit (e.g. coke in hydrocarbon catalysis) for the pore structure determined for a 10 × 10 set of network elements for the pellet under study. The analysis shows how the build-up of a deposit causes physical blocking of the smaller pores at quite low accumulations of foulant which results in inaccessibility of parts of the interior pore structure. This necessarily results in only partial filling of the pore structure with deposit, with a tendency for greater accumulation towards the pellet exterior. This kind of behaviour is not possible with the parallel bundle model. A detailed comparison of the two pore models in respect of accessible interior volume at various foulant accumulations is presented. The derived network model based upon the penetration curve gives an independent prediction of the mercury porosimeter retraction curve which is in reasonably close agreement with the experimental result, thus confirming the probable utility of the model in predicting and correlating other macroscopic properties of the catalyst pellet.  相似文献   
27.
The TaC–TaB2 composition was sintered by spark plasma (SPS) at 1900–2100°C and applied pressure of 30 MPa. TaC and 2–3 wt% B4C were used as starting powders. Densification process, phase evolution, microstructure and the mechanical properties of the composites were investigated. The results indicated that the TaC–TaB2 composition could be SPS to 97% of theoretical density in 10 min at 2100°C. Addition of B4C leads to an increase in the density sample from 76 to 97%. B4C nano-powder resists grain growth even at high temperature 2100°C. The formation of TaB2/carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The phase formation was associated with carbon and boron diffusion from the starting particles B4C to form TaB2 phases. TaC grain sizes decreased with increase in B4C concentration. Samples with 2.0 wt% B4C composition had highest flexure strength up to 520 MPa. The effect of B4C addition on hardness measured by microhardness has been studied. Hardness of samples containing 3.0 wt% B4C was 16.99 GPa.  相似文献   
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The antioxidant activity of Bene hull oil (BHO) was compared with that of sesame oil (SEO) and rice bran oil (RBO) during the frying process of sunflower oil (SFO) at 180C. The ratio between the polyunsaturated and saturated fatty acids and calculated oxidizability were statistically greater for the SFO (4.26 and 6.48, respectively), followed by the SEO (3.18 and 6.27, respectively), RBO (1.53 and 4.37, respectively) and BHO (0.37 and 1.67, respectively). Peroxide and acid values of the oils studied ranged from 0.34 to 3.07 mEq/kg and from 0.19 to 5.20 mg/g, respectively. Total tocopherols and phenolics contents of the SEO (1093.28 and 1042.43 mg/kg, respectively) were significantly higher than those of the SFO (740.27 and 38.68 mg/kg, respectively), BHO (573.41 and 276.67 mg/kg, respectively), and RBO (832.98 and 67.98 mg/kg, respectively). In total, based on the conjugated diene value and carbonyl value measurements during the frying process, the BHO showed an antioxidant activity higher than those of the SEO and RBO at the level of 2%, and the levels higher than 2% of the antioxidative oils caused to decrease the oxidative stability of the SFO, indicating the pro-oxidant effect of the oils added at these levels.

PRACTICAL APPLICATIONS


This research introduces the oil obtained from the hull of Bene, a species of pistachio growing wild in Iran, as a new source of vegetable oil for human nutrition with antioxidant activity significantly higher than sesame and rice bran oils, which are considered as very stable and antioxidative vegetable oils because of the presence of very strong indigenous antioxidants, during the frying process.  相似文献   
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