疲劳损伤谱时域、频域计算方法及其等效性验证

目的 验证疲劳损伤谱时域计算方法与频域计算方法的等效性.方法 将疲劳损伤谱的时域方法与频域方法编写为MATLAB程序,以典型载荷加速度功率谱为例,反推其加速度时程,分别用加速度功率谱、加速度时程数据通过频域及时域方法计算疲劳损伤谱,对比疲劳损伤谱曲线,从而验证时域算法与频域算法的等效性.结果 疲劳损伤谱的低频部分,时域方法得到的疲劳损伤大于频域结果;高频部分,时域算法与频域算法得到的曲线结果基本一致.结论 疲劳损伤谱的时域算法与频域算法具有等效性.     

Effects of meteorological conditions and topography on the bioaccumulation of PAHs and metal elements by native lichen (Xanthoria parietina)

The bioaccumulation of PAHs and metal elements in the indigenous lichens Xanthoria parietina was monitored during two years at a quarterly frequency, in 3 sites of contrasted anthropic influence. The impact of the meteorological factors (temperature, relative humidity, rainfall, wind speed) was first estimated through principal component analysis, and then by stepwise multilinear regressions to include wind directions. The pollutants levels reflected the proximity of atmospheric emissions, in particular from a large industrial harbor. High humidity and mild temperatures, and in a lower extent low wind speed and rainfall, also favored higher concentration levels. The contributions of these meteorological aspects became minor when including wind direction, especially when approaching major emission sources. The bioaccumulation integration time towards meteorological variations was on a seasonal basis (1–2 months) but the wind direction and thus local emissions also relied on a longer time scale (12 months). This showed that the contribution of meteorological conditions may be prevalent in remote places, while secondary in polluted areas, and should be definitely taken into account regarding long-term lichen biomonitoring and inter-annual comparisons. In the same time, a quadruple sampling in each site revealed a high homogeneity among supporting tree species and topography. The resulting uncertainty, including sampling, preparation and analysis was below 30% when comfortable analytical conditions were achieved. Finally, the occurrence of unexpected events such as a major forest fire, permitted to evaluate that this type of short, although intense, events did not have a strong influence on PAH and metals bioaccumulation by lichen.     

西藏日太阳总辐射估算模型的优化与时间尺度效应

根据2012～2014年拉萨站点的日太阳辐射观测数据,对3种日太阳总辐射估算模型(左大康、Prescoff和王炳忠等提出的估算模型)的估算结果和实际观测结果进行误差检验分析,结果表明:3种模型都通过了显著性检验,其平均绝对误差(MAE)分别为6.17 MJ/(m~2·d)、6.42 MJ/(m~2·d)和12.31 MJ/(m~2·d),均方根误差(RMSE)分别为1.60 MJ/(m~2·d)、1.65 MJ/(m~2·d)和2.78 MJ/(m~2·d),表明利用地理位置信息和日照时数的左大康估算模型对拉萨日太阳总辐射的估算效果优于Prescoff和王炳忠估算模型。利用左大康估算模型分别估算得到2015年拉萨、那曲和葛尔地区的日太阳总辐射值,并进行模型验证。通过分析拉萨1971～2015年的太阳总辐射变化和周期性特征,研究日太阳总辐射估算模型的时间尺度效应。按照11年和四季两种不同的时间尺度,利用线性回归法对日太阳总辐射估算结果和实际观测结果进行误差和相关性分析,得到经验参数a和b的值与时间尺度有一定关系。11年和四季两种时间尺度除夏季以外,其他时间拟合模型的精度均得到了提高。通过线性回归法得出45年的西藏日太阳总辐射优化估算模型,该模型估算日太阳总辐射的误差小于左大康模型,估算精度较高。     

动态载荷作用下大型复杂结构的振动疲劳分析方法综述

首先从目前存在的疲劳损伤现象拓展到工程各行业中服役结构的疲劳损伤情况,分析了振动疲劳损伤作用机理,并论述了振动疲劳研究的意义,阐述了振动疲劳的定义,其次分析了振动疲劳分析方法的国内外发展情况及研究现状。此外,通过对振动疲劳研究相关文献的梳理,总结出一些振动疲劳时域与频域方面的研究方法,并分析了各方法的优缺点。最后,根据在振动疲劳研究目前存在的一些问题,归纳出未来的研究发展方向。     

酸化时间对磁性碳纳米管制备及吸附菲的影响

采用共沉淀法对混酸氧化的多壁碳纳米管（MWCNTs）进行磁化,形成了Fe₃O₄/MWCNTs磁性复合材料（MMWCNTs）.研究了酸化时间对MMWCNTs制备及其吸附水中菲性能的影响.结果表明：弱酸条件下吸附效果较好,MMWCNTs对水中菲的吸附在30min内快速上升,到60min时基本达到平衡,吸附过程符合准二级动力学模型.MMWCNTs对水中菲的饱和吸附量随酸化时间增加呈现先升高后降低的趋势.酸化7h后制备的MMWCNTs的饱和吸附量最大,达到17.56μg/mg.     

双滤料曝气生物滤池污水深度处理的研究

采用陶粒、沸石为滤料的曝气生物滤池对生物处理系统二级出水进行深度处理回用,研究了水力停留时间、气水体积比对污染物COD和NH3-N处理效果的影响。结果表明：水力停留时间为8 h,气水体积比为3∶1的工况下,处理效果较好。稳定运行后,出水COD、BOD5、SS、NH3-N、TP和色度平均值分别为15.6 mg/L、3.2 mg/L、8.5 mg/L、1.24 mg/L、0.40mg/L和8度,达到《城市污水再生利用—城市杂用水水质》（GB/T 18920-2002）标准,出水可用于道路清扫、绿化等。     

粤港澳大湾区旅游竞争力与城市化的耦合协调度及其对地方经济的影响

研究旅游竞争力与城市化的耦合协调效应对地方经济的影响具有重要意义。以粤港澳大湾区为例,利用2007—2019年的时间序列数据,构建旅游竞争力—城市化的耦合协调度评价模型,通过固定效应模型检验耦合协调度与地方经济之间的因果关系,最后利用VAR模型作进一步分析。研究发现：（1）粤港澳大湾区旅游竞争力和城市化的耦合协调度在波动中上升,不同地区波动时点和波幅存在差异;（2）地方经济增长和耦合协调度间呈现正相关,在时间序列上存在长期稳定关系;（3）广州、东莞、江门和澳门的耦合协调度对地方经济产生显著的冲击效应与方差贡献,其中广州和澳门的响应积极迅速,东莞存在滞后性,江门波动较大。研究结果对建成“宜居宜业宜游”湾区具有一定参考价值。     

厌氧/微好氧与A/(O/A)n运行时间配比对SNDPR的影响

在SBR反应器中采用厌氧/微好氧与A/（O/A）_n交替运行模式,考察运行过程中污染物的去除效果、颗粒污泥特性及EPS分泌情况等,探讨厌氧/微好氧与A/（O/A）_n的运行时间配比对短程硝化反硝化除磷（SNDPR）系统的影响.结果表明,在厌氧/微好氧与A/（O/A）_n交替运行方式下,整个运行期间对COD的平均去除率始终保持在90%以上.当厌氧/微好氧与A/（O/A）_n运行时间配比为1：1时,系统内的脱氮除磷性能均有所提高,TP和TN的平均去除率分别达到了95.87%和92.00%,颗粒污泥的结构更为密实,EPS含量达到了92.60mg/gVSS,PN/PS维持在较高水平,而运行时间配比为1：3和3：1时颗粒的稳定性均略有降低.系统内以亚硝酸盐为电子受体的反硝化聚磷菌占比达到了57.76%,比氨氧化速率（以N/VSS计）达到了4.57mg/（g·h）,表明厌氧/微好氧与A/（O/A） n运行时间配比为1：1时提高了功能菌的活性,有利于维持良好的短程硝化反硝化除磷性能.     

Investigations on explosion characteristics of ethyl acetate

In this study, the confined explosion characteristics of ethyl acetate were investigated in a constant volume explosion vessel using the initial pressure of 1–4 bar, the initial temperature of 358–418 K, and the equivalence ratio of 0.8–1.4. It was revealed that the peak explosion pressure and the maximum pressure rise rate of ethyl acetate increased as the initial pressure increased and the initial temperature decreased. The peak explosion pressure and maximum pressure rise rate were obtained at the equivalence ratio of 1.2 due to increased heat release rate. Furthermore, the explosion time decreased as the initial pressure decreased. In summation, EA experimental and theoretical deflagration index were investigated and compared. The experimental deflagration index showed that EA explosion was less dangerous, whereas the theoretical deflagration predicted that the explosion could be more hazardous.     

Analysis of herbicide residues by gas chromatography

The extraction and clean‐up, and gas Chromatographic conditions for the detection and determination of herbicides, their metabolites and related compounds are reviewed. The literature material is examined critically in the text and presented in tabular form for quick reference. The section dealing with extraction/clean‐up techniques is sub‐divided with respect to water, soil, plant material, animal, fish and micro‐organisms. Under eight herbicide group headings the important gas Chromatographic parameters such as stationary phase, support phase, column temperature and mode of detection are tabulated. Also tabulated are the application of various detectors to herbicide analyses and limits of detection where information was available. Most commonly used liquid and support phases are listed and their frequency of use given. Different aspects of derivative formation used for the positive identification and quantitation of herbicides are discussed with emphasis on esterification, alkylation and silylation. Other important conversion techniques are outlined, particularly those associated with enhancement of sensitivity e.g. bromination, iodination, dinitrophenylation etc. Efforts that have been made towards general and automated analytical methods are discussed.