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51.
某基坑工程的设计是在原方案基础上修改而成。通过对边坡稳定安全系数的计算和围护桩的一维杆系有限元分析,新的围护方案在充分利用原有围护桩的情况下,采用在坑内注浆加固、增加角撑、大深度放坡开挖等技术措施,达到了安全、经济与可行的目的。 相似文献
52.
Distributions of polycyclic aromatic hydrocarbons in surface waters, sediments and soils of Hangzhou City, China 总被引:35,自引:0,他引:35
Ten polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in 17 surface water samples and 11 sediments of four water bodies, and 3 soils near the water-body bank in Hangzhou, China in December 2002. It was observed that the sum of PAHs concentrations ranged from 0.989 to 9.663 microg/L in surface waters, from 132.7 to 7343 ng/g dry weight in sediments, and from 59.71 to 615.8 ng/g dry weight in soils. The composition pattern of PAHs by ring size in water, sediment and soil were surveyed. Three-ring PAHs were dominated in surface waters and soils, meanwhile sediments were mostly dominated by four-ring PAHs. Furthermore, PAHs apparent distribution coefficients (K(d)) and solid f(oc)-normalized K(d) (e.g. K(oc)= K(d) / f(oc)) were calculated. The relationship between logK(oc) and logK(ow) of PAHs for field data on sediments and predicted values were compared. The sources of PAHs in different water bodies were evaluated by comparison of K (oc) values in sediments of the river downstream with that in soils. Hangzhou section of the Great Canal was heavily polluted by PAHs released from industrial wastewater in the past and now PAHs in sediment may serve as sources of PAHs in surface water. PAHs in Qiantang River were contributed from soil runoff. Municipal road runoff was mostly contributed to West Lake PAHs. 相似文献
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随着电动汽车(EVs)大规模接入电网,其充放电行为的随机性将给电力调度带来新的问题。在研究电动汽车与电网间信息、能量交互机制的基础上,深入分析EV集群运行模式及其对电力系统发电调度的影响。基于低碳经济理念,以电力系统发电能耗成本、CO_2排放费用和V2G服务补贴费用最小化为目标函数,综合考虑EV行驶需求、碳排放配额、碳排放交易机制等相关约束,建立低碳经济环境下EV集群与电力系统间的协调优化运行模型。采用所建模型对10机系统进行仿真分析,优化结果验证了模型的合理性和有效性。 相似文献
55.
The influences of heat treatment and test condition on the microstructure and stress rupture properties of a Ni-Mo-Cr-Fe base corrosion-resistant superalloy have been investigated in this paper. Optical microscope and scanning electron microscope were employed for the microstructure observation, and X-ray diffraction, electron probe micro-analyzer, and transmission electron microscope were used for phase determination. It was found that the grain size increased and the volume fractions of initial M6C carbides decreased along with the increase in solution treatment temperature. When tested at 650 °C/320 MPa, the stress rupture lives decreased with the increase in solution treatment temperature, but the stress rupture lives increased slightly at first and then decreased for the samples solution heat treated at 1220 °C when tested at 700 °C/240 MPa. The elongations showed the descendent trends under these two conditions. The stress rupture life and elongation for the aged samples all showed a noticeable improvement at 650 °C/320 MPa, but there was no noticeable improvement at 700 °C/240 MPa. The reasons can be attributed to the grain size, test conditions, and the initial and secondary carbides. 相似文献
56.
Liu Xiao-fu Lou Yan-chun Yu Bo Su Gui-qiao Li Chang-chun Guo Xin-li Li Biao Shui Guo-yan 《中国铸造》2019,16(1):23-30
In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling(LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength(the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature(1,520 ℃ for upper region and 1,500 ℃ for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring(3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation 001, resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate. 相似文献
57.
采用热分解法在Ti基上被覆了IrO_2+ZrO_2氧化物涂层。通过XRD、SEM、EDX、XPS和循环伏安法等分析了退火温度对IrO_2-ZrO_2二元氧化物涂层的物相、表面形貌和电容性能的影响,引用非线性方程q~*(v)=A_1exp~(-v/t_1)+A_2exp~(-v/t_2)+y_0计算了涂层的内外活性点。结果表明:IrO_2-ZrO_2涂层的临界晶化温度为340~360℃,340℃退火的涂层物相为非晶结构,360℃退火,含有晶态和非晶态2种结构组织,其离子价态为Ir~(3+)、Ir~(4+)以及过饱和IrO_(2+x)(x0)。电容性能随着温度的升高呈先增大后减小变化,360℃退火的电极有最大的电容值,与其"非晶态/晶态"两相共存组织结构有关。涂层中质子迁移能力比电子导电能力对电容的影响要大,扫描速度对质子迁移的影响大于对电子导电的影响。 相似文献
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59.
针对齿轮箱故障信号的多分量多频调制特点,提出了一种基于奇异值分解的最优小波解调技术。首先,采用小波变换的最小Shannon熵作为时间尺度分辨率的度量指标,将其应用到Morlet分析小波的参数优化选择中;其次,对常规小波参数选择方法进行了改进,利用奇异值分解技术对最优小波变化尺度进行了迭代搜索。该方法可以很好地降低噪声信号,有效提取信号中的周期成分,具有较好的瞬态信息提取能力。试验结果也表明了该方法在齿轮箱故障特征提取中的重要性以及降噪方法的有效性。 相似文献
60.