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1.
The Mg3−xZnxSb2 phases with x=0-1.34 were prepared by direct reactions of the elements in tantalum tubes. According to the X-ray single crystal and powder diffraction, the Mg3−xZnxSb2 phases crystallize in the same P3¯m1 space group as the parent Mg3Sb2 phase. The Mg3−xZnxSb2 structure is different from the other substituted structures of Mg3Sb2, such as (Ca, Sr, Ba) Mg2Sb2 or Mg5.23Sm0.77Sb4, in a way that in Mg3−xZnxSb2 the Mg atoms on the tetrahedral sites are replaced, while in the other structures Mg on the octahedral sites is replaced. Thermoelectric performance for the two members of the series, Mg3Sb2 and Mg2.36Zn0.64Sb2, was evaluated from low to room temperatures through resistivity, Seebeck coefficient and thermal conductivity measurements. In contrast to Mg3Sb2 which is a semiconductor, Mg2.36Zn0.64Sb2 is metallic and exhibits an 18-times larger dimensionless figure-of-merit, ZT, at room temperature. However, thermoelectric performance of Mg2.36Zn0.64Sb2 is still poor and it is mostly due to its large electrical resistivity. 相似文献
2.
Hamed Rashidi Ali Ahmadpour Fatemeh F. Bamoharram Seyed Mojtaba Zebarjad Majid M. Heravi Faranak Tayari 《Chemical Papers》2014,68(4):516-524
ZnO nanostructures were synthesised in a hydrothermal reaction of zinc acetate in the presence of molybdophosphoric acid (H3[PMo12O40]) as well as its vanadium-substituted acid (H4[PMo11VO40]) at various times, temperatures, and concentrations. The ZnO nanostructures were characterised by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results demonstrated that the synthesised products are crystalline with a zincite hexagonal phase. Various ZnO nanostructures, such as nanoparticles, microrods, and nanosheets, were produced by changing the experimental conditions. The photocatalytic degradation of methyl orange was also investigated using the ZnO nanoparticles thus prepared. These particles exhibited high performance in the photocatalytic degradation of MO and almost 100 % decolourisation occurred within only 20 min. 相似文献
3.
Evaluating, ranking and selecting of good supplier play an important role in decreasing of buying risk and increasing of efficiency
and effectiveness in value chain and competitive ability of organizations. The goal of this paper is determination and localization
of criteria, ranking and selecting suppliers in Automobile Manufacturing Companies in Iran. Based on literature review, 27
criteria were selected and localized, then using factor analysis, they were decreased to 6 items including quality, delivery,
technical skill, after sales services, investment and product design. Ultimately, 4 suppliers including Tavan, Borna, Saba
and Niroogostaran have been assessed and ranked by fuzzy topsis technique. The results of the research state that score of
Borna is better than others with coefficient of 0.52, and from this view, Tavan, Saba and Niroogostaran are in the next ranking
with coefficient of 0.45, 0.41, 0.31, respectively. Finally, it concludes some remarks including discussion, summary of implications
for managers about how they can use this research results for selecting the best supplier and promoting the competitive ability
of their organization, and directions for their further work too. 相似文献
4.
We present a model for describing the growth of students’ understandings when reading a proof. The model is composed of two main paths. One is focused on becoming aware of the deductive structure of the proof, in other words, understanding the proof at a semantic level. Generalization, abstraction, and formalization are the most important transitions in this path. The other path focuses on the surface-level form of the proof, and the use of symbolic representations. At the end of this path, students understand how and why symbolic computations formally establish a claim, at a syntactic level. We make distinctions between states in the model and illustrate them with examples from early secondary students’ mathematical activity. We then apply the model to one student’s developing understanding in order to show how the model works in practice. We close with some suggestions for further research. 相似文献
5.
Meccanica - In the present study, the two-phase gas–liquid convective heat transfer is numerically studied inside uniformly heated wavy micro-tubes in the Taylor flow regime. Both Newtonian... 相似文献
6.
Ahmadpour Javad Ahmadi Mahyar Javdani Amirhossein 《Journal of Thermal Analysis and Calorimetry》2019,135(3):1943-1949
Journal of Thermal Analysis and Calorimetry - Nowadays, most of the world’s energy consumption is from fossil fuels. One of these fossil fuels is natural gas condensate which consists of... 相似文献
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8.
Toutounchian Nafiseh Ahmadpour Ali Heravi Majid M. Bamoharram Fatemeh F. Ayati Ali Deymeh Fatemeh 《Research on Chemical Intermediates》2016,42(4):3283-3301
Research on Chemical Intermediates - Alkylation of benzene with 1-decene for production of linear alkylbenzene in the presence of nanotitania (n-TiO2)-supported Dawson heteropolyacids was studied.... 相似文献
9.
The catalytic effects of two forms of nano‐TiO2, which are prepared via an ordinary or a magnetized process, are investigated in the synthesis of pyridine dicarbonitriles by one‐pot multicomponent reaction of 4‐methyl thiophenol, malononitrile, and aryl aldehydes. The results have shown that both prepared nano‐TiO2 exhibited high catalytic activities toward the synthesis of pyridine dicarbonitrile derivatives but the nano‐TiO2, which is prepared via a magnetized process, has shown better catalytic activity. Furthermore, this new catalytic method for the synthesis of pyridine dicarbonitriles provides rapid access to the desired compounds in high yields and so a simple work‐up procedure in the presence of water at room temperature. Therefore, this method represents a significant improvement incompatible of the other methods that are available for the synthesis of pyridine dicarbonitriles. 相似文献
10.
Manganese(Ⅲ) meso-tetraphenylporphyrin acetate [Mn(TPP)OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with (diacetoxyiodo)benzene [Phl(OAc)2] in CH2C12-H2O(95:5,volume ratio),The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn(TPP)OAc,In the former case,the formation of carbonyl products was complete within just a few minutes with >97% selectivities,and no further oxidation of the produced aldehydes was achieved under these catalytic conditions,This method provides a benign procedure owing to the utilization of low toxic(diacetoxyiodo)benzene,biologically relevant manganese porphyrins,and carboxylic acids. 相似文献