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学习体验是学生对学习内容、过程、方法、意义的自我感受和评估,对学生学习志趣、学习素养提升有积极正向作用。以钠及其化合物复习为例,将各类别物质间转化关系的构建、物质制备原理和条件的优选作为学习体验对象,依据学习体验的内在发展历程设计学习任务及活动,引导学生亲身体验学科认知方式、学科思维方法、学科应用价值,评价体验结果,激励学生自主学习发生。 相似文献
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计算表明,与场的相干态类似的原子相干态,具有不同于场的相干态的压缩行为;进一步证明:直接类比于(?)(ξ)不能得到“原子压缩算符”. 相似文献
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This present work focused on preparation of economic and high performance reverse osmosis membranes, characterized by high transport properties (salt rejection and flux) towards desalination of brackish water. In this respect cellulose acetate from sugar-cane bagasse (BCA) and polymethyl methacrylate (PMMA) wastes were used as the substrates of membrane. The function of PMMA for enhancing the performance of bagasse-based cellulose acetate RO-membranes was investigated at operating pressure 35.85 bar and feed temperature 25 °C. The effects of casting solution, percentage of polymer and treatment of polymer by alkali (HPMMA) on the performance of RO-membrane were discussed. The preferable composition (wt.%) of the 90% BCA and 10% HPMMA was achieved salt rejection 92.18% and flux 325.9 l h−1 m−2. High water purity was obtained by pre-passing the salted water through membrane made from dissolved bagasse (methylol cellulose) together with PMMA, instead of ion exchanger, followed by passing the accepted water through BCA–HPMMA membrane, whereas the salt rejection increased to 98%. Also, by this approach we obtained high thermal stability membrane compared to CA-RO-membrane. This data gives highlight on possibility of application such type of membrane with high temperature operation conditions. 相似文献
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Abouel-Enein S El-Saied FA Emam SM Ell-Salamony MA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(2):421-429
Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of salicylidene-N-cyano-acetohydrazone H2L1 and 2-hydroxy-l-naphthylidene-N-cyanoacetohydrazone H2L2 have been prepared in ethanolic solution and characterized by analytical, spectral, magnetic susceptibility, molar conductivity and TGA measurements. The analytical data show that all the complexes derived from H2L1 and H2L2 are formed in molar ratios 1M:2L, except the complexes of Mn(II), Co(II) and Cu(II) acetates of H2L2 and the complexes of Mn(II), Co(II) and Ni(II) acetates and CuCl2 of H2L1 are formed in 1:1 molar ratios. The conductance data show that all metal complexes are non-electrolytes. Electronic absorption spectra and magnetic susceptibility measurements proved that the prepared complexes have octahedral configuration except [Co(HL2)OAc] which has tetrahedral structure. The ligand field parameters were calculated for the Co(II) and Ni(II) complexes and the data show that the covalent character of the metal ligand sigma-bond is low. The ESR parameters of the Cu(II) complexes at room temperature were calculated. Thermal TGA for some solid complexes are reported. 相似文献
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El-Sawaf Ayman K. West Douglas X. El-Bahnasawy Ramadan M. El-Saied Fathy A. 《Transition Metal Chemistry》1998,23(3):227-232
The synthesis and characterization of complexes of iron(III), cobalt(II) and cobalt(III) with 4-formylantipyrine N(4)-methyl-, N(4)-dimethyl-, and 3-piperidylthiosemicarbazones are reported. Elemental analyses, molar conductivities, magnetic measurements
and spectral (i.r., electronic and e.s.r.) studies have been used to elucidate the nature of the metal complexes. The i.r.
spectra show that the thiosemicarbazones behave as bidentate or tridentate ligands, either in the thione or thiolato form.
Different stereochemistries are proposed for the various cobalt(II) complexes on the basis of spectral and magnetic studies.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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建立了超高效液相色谱-电喷雾离子源-串联三重四极杆质谱(UPLC-ESI MS/MS)分析饮用水中高氯酸盐的方法.以300Extend-C18为分析柱,10%甲醇水溶液为流动相,ESI MS/MS串联质谱为检测器,以多重反应监测(MRM)模式监测高氯酸盐m/z 99.5→82.9离子对.方法的线性范围为0.2 ~10 μg/L,相关系数为r2=0.999 9,方法检出限为0.15 μg/L,平均加标回收率为82%,相对标准偏差为4.4%.应用UPLC-ESI MS/MS法测定北京市部分城区饮用水中的高氯酸盐,其中5个水样中检出ClO-4,质量浓度为0.040 ~0.262 μg/L,但在安全阈值范围内,不会对居民健康构成威胁. 相似文献