Idées fixes

Three examples are given of views considered by the author to be misconceptions.     

工程竣工造价结算审核策略探究

工程竣工结算审核是工程造价结算的必要途径,通过竣工造价结算可以有效地控制整个工程的造价,节省不必要的支出。本文针对工程竣工造价审核中的特点和问题进行了分析,并提出了相应的解决对策。     

浅析城市旧桥拓宽横向连接形式

本文介绍了旧桥拓宽的一般原则,分析了桥梁拓宽不同横向连接方式的特点。桥梁拓宽一般包括三种方式：上下均不连接的拓宽方式、上下均连接的拓宽方式和上部连接下部不连接的拓宽方式。     

淮蚌线淮河大跨越输电塔有限元建模和修正研究

超高压大跨越输电塔构成复杂,且具有塔体高、档距大等特点,对地震、风以及导线覆冰等效应的反应灵敏。为了对其进行结构健康监测和安全评估问题的研究,需要建立能够较准确反映结构动力特性的模型。通过对淮蚌线淮河某500kV大跨越输电塔有限元模型的建立及动力特性参数的计算,结果表明:计算结果与实测结果存在较大误差,从质量、刚度及边界条件等角度进行分析,进而对有限元模型进行修正。修正后计算动力特性参数与现场测试结果基本吻合,为进一步开展输电塔结构安全评估提供了基准模型。     

基于PRO/E Wildfire4.0冰箱扣手注射模具的设计

介绍了利用Pro/E4.0软件进行塑料模具设计的基本思路,并以冰箱扣手为实例,阐述了利用Pro/E应用模块EMX5.0进行设计的过程,重点讲述了斜导柱哈夫、斜顶杆等抽芯机构的设计,结果表明该软件的应用与传统设计方法相比,具有较大的优势和参考价值。     

基于Pro/e与ANSYS WORKBENCH的复杂装配件协同仿真及优化

针对单一环境下复杂装配件设计过程存在的局限性,提出了基于Pro/e与ANSYSWORKBENCH协同仿真及优化的解决方案。对Pro/e与ANSYS WORKBENCH协同仿真及优化过程的关键技术——参数化建模、参数传递、接口问题、连接问题、网格策略及优化方案进行了系统的研究。并给出了一个基于该方案的复杂装配件设计、分析及优化的应用案例。初步的实践表明该方案可以有效的解决复杂装配件设计、分析及优化问题。     

Hydrodynamics characterization of the Maxblend impeller

The hydrodynamic characteristics of the Maxblend^TM impeller have been investigated in the case of viscous Newtonian fluids. Both laboratory experiments and 3D finite element based computational fluid dynamics (CFD) simulations have been carried out. The power consumption, the mixing evolution yielding the mixing time, and the effect of baffles in the laminar and transition flow regimes have been determined. It was found that the limit Reynolds number between the laminar and transition regimes is approximately 25 and 38 for the unbaffled and baffled configurations, respectively. Based on the range of Reynolds numbers studied in this work, the best window performance of the Maxblend^TM mixer where fast and homogenous mixing is achieved is the end of the laminar regime and the early transition regime with baffles.     

Dynamic modeling and simulation of absorption of carbon dioxide into seawater

In order to elucidate the dynamic performance of the CO₂ ocean disposal process, effects of operating parameters, such as gas flow rate, salinity and temperature, on the absorption of CO₂ into seawater were examined. The rate-based model consisting of the rates of chemical reaction and gas-liquid mass transfer was developed for simulating dynamic process of CO₂ ocean disposal. In modeling, non-ideal mixing characteristics in the gas and liquid phases are described using a tanks-in-series model with backflow. Experiments were performed to verify dynamic CO₂ absorption prediction capability of the proposed model in a cylindrical bubble column. The operation was batch and continuous with respect to liquid phase and gas phase, respectively. Experimental results indicate that the CO₂ gas injection rate increased the absorption rate but the increase in salinity concentration caused inhibition of the absorption of CO₂. The proposed model could describe the present experimental results for the dynamic changes and the steady-state values of dissolved CO₂ concentration and hydrogen ion concentration. The proposed model might effectively handle the prediction of the absorption of CO₂ into seawater in the CO₂ ocean disposal.     

The effect of specific surface area on the activity of nano-scale ceria catalysts for methanol decomposition with and without steam at SOFC operating temperatures

Nano-particulate high surface area CeO₂ was found to have a useful methanol decomposition activity producing H₂, CO, CO₂, and a small amount of CH₄ without the presence of steam being required under solid oxide fuel cell temperatures, 700-1000 °C. The catalyst provides high resistance toward carbon deposition even when no steam is present in the feed. It was observed that the conversion of methanol was close to 100% at 850 °C, and no carbon deposition was detected from the temperature programmed oxidation measurement.The reactivity toward methanol decomposition for CeO₂ is due to the redox property of this material. During the decomposition process, the gas-solid reactions between the gaseous components, which are homogeneously generated from the methanol decomposition (i.e., CH₄, CO₂, CO, H₂O, and H₂), and the lattice oxygen on ceria surface take place. The reactions of adsorbed surface hydrocarbons with the lattice oxygen ( can produce synthesis gas (CO and H₂) and also prevent the formation of carbon species from hydrocarbons decomposition reaction (C_nH_m⇔nC+m/2H₂). V_O^·· denotes an oxygen vacancy with an effective charge 2⁺. Moreover, the formation of carbon via Boudouard reaction (2CO⇔CO₂+C) is also reduced by the gas-solid reaction of carbon monoxide with the lattice oxygen .At steady state, the rate of methanol decomposition over high surface area CeO₂ was considerably higher than that over low surface area CeO₂ due to the significantly higher oxygen storage capacity of high surface area CeO₂, which also results in the high resistance toward carbon deposition for this material. In particular, it was observed that the methanol decomposition rate is proportional to the methanol partial pressure but independent of the steam partial pressure at 700-800 °C. The addition of hydrogen to the inlet stream was found to have a significant inhibitory effect on the rate of methanol decomposition.