电建项目价格评标方法分类及其选用

价格评标方法是电建项目招投标最重要的内容, 文章对其进行了汇总分类, 指出了各类优缺点,列举了相关案例, 并分析了有关选用原则, 以便于借鉴。     

胶原蛋白涂覆棉纤维的研究

胶原蛋白具有独特的3股螺旋结构,优越的生物相容性和生物降解性,极具应用前景。为了进一步拓展纤维素的应用领域和开发新型绿色纤维素纤维,采用高碘酸钠对棉纤维进行局部有限选择性氧化,然后与胶原蛋白溶液反应,制备了涂覆胶原蛋白棉纤维。结果表明:经高碘酸钠有限氧化后棉纤维的断裂强度降低不明显;胶原蛋白分子通过席夫碱C N双键共价结合在棉纤维表面。     

Heat-insulating composite based on unwoven materials and organomineral binder

Composites based on unwoven cellulose-hydrate and carbon materials and an organomineral binder have been developed and investigated. Optimal compositions of the composites feature a higher fire resistance, a low density, and effective thermophysical characteristics. The composites are promising for use as heat-insulating materials with a rigid structure in different branches of the national economy and industry. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 85–91, January–February, 2009.     

Adding carbon nanotubes and integrating with AA5052 aluminium alloy core to simultaneously enhance stiffness, strength and failure strain of AZ31 magnesium alloy

New bimetal AZ31-CNT/AA5052 macrocomposite comprising: (a) carbon nanotube (CNT) reinforced magnesium alloy AZ31 shell and (b) aluminium alloy AA5052 millimeter-scale core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterisation revealed more rounded intermetallic particle of decreased size, reasonable CNT distribution, and dominant (1 0 −1 1) texture in the longitudinal and transverse directions in the AZ31-CNT nanocomposite shell. Interdiffusion of Mg and Al across the core-shell macrointerface into each other was also significant. Compared to monolithic AZ31, the AZ31-CNT shell had significantly higher hardness (+30%). In tension, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased stiffness (+39%), ultimate strength (+13%), failure strain (+17%) and work of fracture (+27%) of AZ31, while yield strength (−2%) was marginally decreased. In compression, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased yield strength (+35%), failure strain (+42%) and work of fracture (+70%) of AZ31, while ultimate strength (+1%) was marginally increased. The effect of joint presence of: (a) CNT (in the AZ31 shell) and (b) AA5052 millimeter-scale core on tensile and compressive properties of AZ31 is investigated in this paper.     

工程量清单招投标中成本界定方法之研究

介绍了工程量清单招投标中采用“经评审最低价中标法”的一些做法和特点,认为当前招投标中的“拦路虎”是成本界定问题。通过目前常见几种界定方法之比较,提出清单报价综合评判法是成本界定行之有效的方法,并提出成本界定具体做法以及应注意的问题。     

Liquid Phase Oxidation of Toluene to Benzaldehyde with Molecular Oxygen over Copper‐Based Heterogeneous Catalysts

We conducted the liquid phase oxidation of toluene with molecular oxygen over heterogeneous catalysts of copper‐based binary metal oxides. Among the copper‐based binary metal oxides, iron‐copper binary oxide (Fe/Cu=0.3 atomic ratio) was found to be the best catalyst. In the presence of pyridine, overoxidation of benzaldehyde to benzoic acid was partially prevented. As a result, highly selective formation of benzaldehyde (86% selectivity) was observed after 2 h of reaction (7% conversion of toluene) at 463 K and 1.0 MPa of oxygen atmosphere in the presence of pyridine. These catalytic performances were similar or better than those in the gas phase oxidation of toluene at reaction temperatures higher than 473 K and under 0.5–2.5 MPa. It was suggested from competitive adsorption measurements that pyridine could reduce the adsorption of benzaldehyde. At a long reaction time of 4 h, the conversion increased to 25% and benzoic acid became the predominant reaction product (72% selectivity) in the absence of pyridine. The yield of benzoic acid was higher than that in the Snia‐Viscosa process, which requires corrosive halogen ions and acidic solvents in the homogeneous reaction media. The catalyst was easily recycled by simple filtration and reusable after washing and drying.     

Microwave‐Assisted Fast Cyclohexane Oxygenation Catalyzed by Iron‐Substituted Polyoxotungstates

Under microwave irradiation, iron‐substituted polyoxotungstates (Fe‐POMs) catalyze cyclohexane oxygenation to A/K oil with 90–95% selectivity, unmatched turnover frequencies (40–400 h⁻¹), and multi‐turnover regime (>1000 TON). Such a rapid reaction protocol allowed the screening of so‐called inorganic Fe‐synzymes with 1–4 nuclearity, including a family of Krebs‐type isostructural complexes. Product distribution, kinetic analysis, mechanistic probes and fitting calculations, are consistent with a radical chain oxidation propagated by Fe‐catalysed decomposition of organic peroxides which ultimately depends on the redox‐properties and structural arrangement of the iron moiety within the POM cage.     

高温树脂基复合材料防护用轻质陶瓷涂层的制备

研究了采用Ni-3％Al粉末和纯铝、纯锌作为打底材料在碳纤维增强聚酰亚胺复合材料(PMC)基体上制备Al2O3轻质陶瓷防护涂层的可行性,测试了涂层的剪切结合强度和耐热循环性能。结果表明,等离子喷涂Ni-3％Al粉末会对PMC基体造成破坏,不适合于作为PMC基体上的打底材料。电弧喷铝也会对基体造成一定程度的破坏,结合强度和耐热循环性能较低。采用低电压、小电流电弧喷锌,可以获得和基体结合良好打底涂层,涂层剪切结合强度达10．45MPa。在其上制备的Al2O3陶瓷防护涂层耐热循环性能良好。     

部分醇解聚乙烯醇纤维的氢键结构

用不同醇解度的聚乙烯醇进行冻胶纺丝 ,得到了醇解度为 99.5 %、93%、86 %的聚乙烯醇纤维 ,研究了不同醇解度下纤维中的氢键及其对纤维力学性能的影响。结果表明 ,相对较低的醇解度可以有效控制纺丝过程中氢键的形成 ,提高易拉伸性和纤维的力学性能。     

几种烷烃和烯烃氨基硝基取代物分子内氨基对C-NO2键影响的理论研究

在B3LYP/6-31G**水平下,研究了烷烃、乙烯及1,3-丁二烯的氨基硝基取代物中不同位置和数量的氨基对C-NO2的影响.结果表明,在氨基硝基烷中,氨基的位置和数量对C-NO2键的影响只能依赖于氨基硝基的诱导效应和空间效应,当二者的间距超过2个C原子时,氨基对C-NO2键的影响将变得很微弱;在氨基硝基乙烯类化合物中,1号位的氨基会削弱C-NO2键;而2号位的氨基加强了C-NO2键,并且随着2号位氨基数目的增加,C-NO2键缩短,C-NO2上C原子的负电性增加(包括正电荷减少),C=C键伸长,τ增加,即氨基的供电子作用和整个分子的共轭效应更加明显;对于氨基硝基1,3-丁二烯类化合物,当分子中硝基氧未与氨基氢形成氢键时,氨基对C-NO2键明显存在类似于苯环的定位效应.当分子中硝基氧与氨基氢形成氢键时,以上效应被削弱,而且在氨基数目相同的条件下随着氢键的增强,C-NO2键被削弱.