High temperature studies of Fe-Mn-Al-C alloys with different manganese concentrations in air and nitrogen

The formation of AIN was studied using a series of Fe-Mn-Al-C alloys with manganese contents from 20 to 40 wt%. All investigations were carried out in air and nitrogen at 1000° C. The permeability (D _N N _N) of nitrogen in Fe-Mn-Al-C alloys was found to be a major factor influencing the formation of AIN precipitates which are always observed underneath the oxide scales of the specimen. The formation of AIN is related to the lower formation rate of Al₂O₃ and high permeability of nitrogen; therefore AIN can only be formed in those alloys with a higher manganese concentration because the specimens are treated in air and in pure nitrogen at 1000 C.     

对资金时间价值的再认识

在对资金时间价值的内涵进行分析的基础上,文章提出了资金时间价值应用中需要注意的一些事项。这对更好地运用时间价值的观念去解决实际问题具有参考价值。     

热回收在全新风除湿机中的节能研究

分析了GB/T20109-2006所述全新风除湿机节能的5个方面:1)冷凝热回收.2)室内回风热回收.3)冷凝水冷回收.4)处理后新风冷回收.5)新风热回收.通过对典型案例做深入探讨发现:采用板翅式热回收器或热管换热器对新风处理后新风进行冷回收预冷新风,能够降低制冷系统冷负荷20％～30％,显著提高全新风除湿机的单位输入功率除湿量.     

活塞式内燃机排气消声器技术特点及发展趋势

活塞式内燃机排气噪声具有声压大、频谱宽的特点,对人们的生活质量有着严重的影响。通过分析摩托车、汽车、工程机械、火车、赛艇、小型飞机等载运工具所用内燃机的功率范围和使用特点,结合其对排气流场的特定要求,总结出消声器的技术特点和发展趋势。     

Plasticized properties of poly (lactic acid) and triacetine blends

Systematically investigations of the plasticizing effects of triacetine (TAc) on crystallization, chain mobility, microstructure, and tensile properties of the Poly (lactic acid)/triacetine (PLA/TAc) blends are reported. A new transition hump was observed on the tan δ curve of PLA_xTAc_y specimens at temperatures ranging from ?80 to ?20°C. Thermal, wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis properties of PLA and PLA_xTAc_y series specimens suggest that PLA and PLA_xTAc_y series specimens can hardly crystallize by cooling the melt in room temperature. However, significant recrystallization of α form PLA crystals was found during the annealing processes of PLA_xTAc_y series specimens. Some “less perfect” β form PLA crystals were found as the TAc contents of PLA_xTAc_y specimens reach 30 wt %. Further morphological analysis show that the inherent brittle deformation behavior of the PLA specimen was successfully transformed into relatively ductile fracture behavior after blending sufficient but optimum amounts of TAc in PLA resins. Possible reasons accounting for this interesting recrystallization, thermal, microstructure and tensile properties of PLA_xTAc_y specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Selectivity recovery of molybdenum(VI) from rhenium(VII) by amine-modified persimmon waste

Amine functional group was grafted to obtain modified persimmon waste gel(NH_2–CPT) with the focus of development of selective recovery of molybdenum from rhenium. The adsorption behavior of the NH_2–CPT gel for various metal ions at varying hydrochloric acid concentrations was studied. It is found that the NH_2–CPT exhibits high affinity for Mo(VI) and no affinity for Re(VII), Cu(II),Fe(III), Mn(VII), and Zn(II) under the operating conditions. The maximum adsorption capacity for Mo(VI) is 172 mgág-1, and the adsorption behavior obeys the Langmuir model. Owing to Mo(VI) as poly-anions, the adsorption mechanism of molybdenum anions could be explained as the anion exchange reactions at weak acid concentration, while neutral molecules could be explained as the complexation reactions at strong acid concentration,respectively. In addition, its excellent adsorption characteristics for Mo(VI) are confirmed by separation of Mo(VI)from Mo to Re containing industrial effluent.     

基于生态环保理念的绿色桥梁设计

随着经济的快速发展，我国桥梁建设以低成本、低污染、质量优、耐久使用、生态环保存为发展目标，走向了绿色设计施工方向。本文结合绿色桥梁设计理念，分析了生态环保的桥梁设计需要，希望能为未来桥梁设计的发展奠定基础。