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991.
络合滴定法测定低压流体输送用镀锌焊接钢管镀锌层重量 总被引:2,自引:0,他引:2
介绍了利用络合滴定法测定低压流体输送用镀锌焊风管镀锌层重量的方法,试样用稀硫酸溶解,在PH1.5 ̄2.0的弱酸性介质中,以磺基水杨酸钠为指标剂,用EDTA滴定铁,调PH为5.5,以PAN为指示剂,用EDTA滴定锌,由EDTA用量求出锌的重量,用GB/T3091-93方法比较,试验结果满意。 相似文献
992.
Yao Chen Panpan Sun Tiancheng Li Yin Zou Yiyong Huang Yongcun Shen 《Tetrahedron letters》2018,59(25):2399-2402
Asymmetric Michael addition between 3-ethyl carboxylate substituted pyrazolones and 5-alkenylthiazolones catalyzed by a series of chiral bifunctional hydrogen bonding organocatalysts was investigated. Good yields (up to 96%) and excellent enantioselectivities (up to 99% ee) were achieved by using a squaramide containing piperidine group derived from (1S, 2S)-cyclohexanediamine. This strategy provides facile access to a diverse library of thiazole-pyrazolone derivatives with potential bioactivity. 相似文献
993.
A systematic study of the uniqueness, reversibility and sensitivity issues associated with seven indentation-based methods of property extraction demonstrates that: (i) The indentation algorithms generally identify the elastic and plastic properties of materials uniquely for most materials. (ii) The indentation forward algorithms (wherein the indention responses are determined from the elastic and plastic properties of the indented materials) and the reverse algorithms (wherein the elastic and the plastic properties of materials are extracted from the indentation responses) are distinct for each indentation method and are internally consistent in that the differences in the elastic and plastic properties determined through the reverse analysis and the ‘true’ material properties are generally small for a large number of materials, for each of the seven methods. (iii) While the differences in the indentation response parameters predicted by each of the seven indentation methods (for a particular material) could be small, there could be considerable dispersion in the elastic and plastic properties predicted by the reverse algorithms of the seven methods (for a particular set of indentation response parameters). (iv) In the forward analysis, small uncertainties in the elasto-plastic properties lead to small uncertainties in the predictions of the indentation response of materials. The sensitivity distribution is generally heterogeneous and symmetric across positive and negative variations in the material elasto-plastic properties. (v) In the reverse analysis, the elastic modulus exhibits low sensitivity, while the yield strength and the strain-hardening exponent generally exhibit high sensitivity to uncertainties in the indentation response parameters. The sensitivity distribution is heterogeneous and asymmetric across positive and negative variations in the indentation response parameters. (vi) The representative stresses are fairly robust to uncertainties in the indentation response parameters. Consequently, dual sharp and spherical indentation methods, which identify multiple representative stresses, exhibit reduced sensitivity in the determination of the plastic properties. 相似文献
994.
The mixture of cesium hydroxide and terminal alkynes in dry DMF in the presence of 4(A°), molecular sieves was stirred for 3.0 h at room temperature under N2, then aryltellurenyl bromide in THF was added, and the reaction mixture was stirred for 2.0 h. Alkynyl tellurides were obtained in about 90% yields by flash chromatography. 相似文献
995.
Tianwen Chen Fengfu Fu Zhixin Chen Danzhen Li Lan Zhang Guonan Chen 《Journal of chromatography. A》2009,1216(15):3217-3222
The intermediates of photodegradation and microbial degradation of pirimicarb insecticide were investigated by liquid chromatography coupled with ion-trap mass spectrometry (LC–IT-MS). Different intermediates were detected in the photodegradation and microbial degradation of pirimicarb. In the photodegradation of pirimicarb in aqueous solution 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167), 2-methylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 224) and 2-formylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 252) were the main products. It was found that 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167) was the major product in the microbial degradation of pirimicarb in soil. 相似文献
996.
Zhongbing Huang Xiaoming Liao Yunqing Kang Guangfu Yin Yadong Yao 《Journal of colloid and interface science》2009,330(2):399-403
Why is it that drops do not slip down inclined thin fibers or spider silks? The possible explanation is based on the existence of fiber size, which causes a sustaining force that pins these drops. Following this explanation, the drop remains in equilibrium until a critical value of the sustaining force is reached. We suggest an alternative analyses, from the point of view of the inclined fiber at which the drop slips down is predicted. This result does not depend explicitly on silk surface roughness, but only on the drop size and surface tensions. 相似文献
997.
We report the first total synthesis of glycyrol. Glycyrol, isolated from Glycyrrhizae Radix, has a unique skeleton of a benzofuran coumarin. The key steps are Smiles rearrangement and selective introduction of prenyl and O-methyl groups. The first application of a novel precursor for Smiles rearrangement, 3-benzyloxy-substituted (diacetoxyiodo)benzene, showed the synthetic possibility for diverse precursors. The introduction of a benzyl protecting group was important because selective deprotection was hard due to the low solubility of intermediates. 相似文献
998.
In this paper, we have proposed a new scheme to generate double-sideband (DSB) optical millimeter-wave (mm-wave) with signal carried only by optical carrier, and its transmission performance is investigated. The theoretical and numerical results show that the DSB optical mm-wave signal generated by our scheme suffers only from the fading effect, the time shift of the sidebands has little influence on its transmission performance. The signal demodulated from the harmonic photocurrent shows a clear and open eye diagram and has good performance even if the transmission distance is very close to but not just at the fading nodes. The theoretical results are in good agreement with our numerical simulation. 相似文献
999.
Li Yin Xiaojing Xu Hongjun Yuan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,59(3):457-474
The aims of this paper are to discuss global existence and uniqueness of solution for a class of non-Newtonian fluids with
vacuum in one-dimensional bounded interval. The important point in this paper is that we allow the initial vacuum. In particular,
these results are used to prove similar results for more general non-Newtonian fluids, and applied to numerical computation.
This work is partially supported by the 985 program of Jilin University, China Postdoctoral Sciences Foundation, and NSF Grant
([10571072]; [10601009]). 相似文献
1000.