实验室条件下温度升高对水体叶绿素a的影响研究

以23℃为基础,按2℃温差设置温度梯度,最高温度组为29℃。每隔10d取样一次,进行叶绿素α浓度的测定。结果显示温度低于25℃时,增温有助于藻类生物量的提高,而温度超过25℃时,增温限制了藻类生物量的提高。水体温度量对浮游植物生物的影响程度与增温幅度和培养时间有关。Pearson相关性分析结果显示:温度与叶绿素a浓度相关性显著(P0.05),叶绿素a浓度与培养时间呈极显著正相关(P0.01)。     

郁江、黔江和浔江广西桂平段水质变化趋势分析

根据2003-2012年水质监测资料,采用秩相关系数法对郁江、黔江和浔江广西桂平段水质变化趋势进行分析。结果表明,黔江和浔江水质呈明显好转趋势;郁江水质呈好转趋势,但不明显。提出了继续加强水污染防治工作的建议。     

盾构施工对不同刚度桩体影响的数值分析

针对苏州轻轨一号线盾构隧道的施工情况,采用三维有限元数值模型,研究了盾构施工对不同刚度桩体的影响.计算结果表明:当盾构施工时,不同刚度桩体均偏向隧道移动,在隧道轴线处的横向位移均为最大.桩身横向位移最大值、竖向位移随桩体刚度增大而变小,桩身轴力、弯矩则随桩体刚度增大而逐渐增大,桩身最大负弯矩均出现在隧道轴线位置处.在盾...     

极端冰雪条件下的顺层岩质边坡滑移稳定性分析

推导了典型岩石边坡在极端冰雪条件下的滑移稳定系数的表达式;通过计算分析,揭示了岩石边坡滑移稳定系数随裂隙内水深、坡高、坡角、滑面倾角等因素变化的规律及与冻深的关系,并绘制岩石边坡滑移稳定系数与边坡几何要素之间的关系图.研究表明,当考虑极端冰雪灾害影响时,岩石边坡滑移稳定系数发生较为明显的变化:随裂隙饱水程度、坡面角、主...     

矸石山的危害及自燃原因关联分析

从不同角度论述了矸石山具有的危害性,尤其是自燃矸石山对空气环境、水质和土壤的污染,通过实验分析矸石山自燃的主要影响因素,指出由于自燃矸石山的管理、治理不当所引发的矸石山坍塌和爆炸等地质灾害事故,给当今煤炭企业发展带来的不可忽视的负面影响,促使企业意识到消除矸石山危害的紧迫性和任务的艰巨性,同时为防止矸石山自燃提供了理论指导和依据。     

桥式起重机典型事故分析及安全管理

分析了桥式起重机典型事故发生机理,运用事故树分析法对桥式起重机事故发生进行了分析,从而为能够找出安全隐患,制定出最优的控制措施提供了理论上的依据.最后根据分析结果,系统地提出了控制危害,降低事故发生率的安全管理措施,提出一些具有可行性的建议.     

大连市化肥农药流失入海量分析

对1996~2000年间,大连市化肥农药使用现状进行了统计分析,运用不同类型有机物理论化学耗氧量的数学计算模型,分别计算了大连市化肥农药流失和工业废水排放对海域的污染影响,结果认为大连市化肥农药流失对海域污染物COD的污染贡献率远远大于工业废水排放的COD贡献率。最终提出应采取加强化肥农药使用管理等有效手段防治近岸海域化肥农药流失污染。     

肥煤自燃全过程热动力学特征参数研究

实验测定了林西矿肥煤样品30~900℃煤自燃全过程热动力学特征参数,得出:TG/DTG曲线显示煤样DTG初始临界温度45℃,干裂温度122℃,活性温度195℃,增速温度265℃,质量极大值温度342℃,着火温度465℃,最大热失重速率温度515℃和燃尽温度690℃;DSC曲线显示,煤样初始放热温度60℃、最大热释放速率温度511℃。结合TG-DTG-DSC曲线综合分析可知,煤温达到510℃左右时煤样反应最剧烈。由煤自燃标志气体测定实验系统得出:煤温130℃后CO,CO 2释放量迅速增加,210℃增加速度下降;CH 4,C 2 H 6含量变化具有规律性且两者变化相近;C 2 H 4出现温度为130℃;C 2 H 4/C 2 H 6比值在190~350℃有较强的规律性,呈上升趋势且上升速度较快;350℃之后,CH 4,C 2 H 6,C 2 H 4体积分数均开始急剧增大;C 2 H 4/CO与C 2 H 4/CO 2变化趋势大致相同,在130~350℃时缓慢增长,达到350℃后比值呈指数形式上升。经拟合曲线,得到活化能的3个突变点温度:70,180,220℃,其中180℃与交叉点温度相吻合。通过以上研究,得到了肥煤自燃全过程的热力学特征参数,为实际生产中防治煤自燃提供了理论依据。     

Comparative analysis of data reduction techniques for questionnaire validation using self-reported driver behaviors

Introduction: Exploratory data reduction techniques, such as Factor Analysis (FA) and Principal Component Analysis (PCA), are widely used in questionnaire validation with ordinal data, such as Likert Scale data, even though both techniques are indicated to metric measures. In this context, this study presents an e-survey, conducted to obtain self-reported behaviors between Brazilian drivers (N = 1,354, 55.2% of males) and Portuguese drivers (N = 348, 46.6% of males) based on 20 items from the Driver Behavior Questionnaire (DBQ) on a five-point Likert Scale. This paper aimed to examine DBQ validation using FA and PCA compared to Categorical Principal Component Analysis (CATPCA) which is more indicative to use with Likert Scale data. Results: The results from all techniques confirmed the most replicated factor structure of DBQ, distinguishing behaviors as errors, ordinary violations, and aggressive violation. However, after Varimax rotation, CATPCA explained 11% more variance compared to FA and 2% more than PCA. We identified cross-loadings among the component of the techniques. An item changed its dimension in the CATPCA results but did not change the structural interpretability. Individual scores from dimension 1 of CATPCA were significantly different from FA and PCA. Individual scores from factor 1 of CATPCA were significantly different from FA and PCA. Practical applications: The CATPCA seems to be more advantageous in order to represent the original data and considering data constrains. In addition to finding an interpretable factorial structure, the representation of the original data is regarded as relevant since the factor scores could be used for crash prediction in future analyses.     

A bibliometric study of pool fire related publications

Pool fire is a common form of fire, which is constantly investigated along with the development of fire science and is also comprehensively employed as stable fire sources in examining other fire scenarios such as building and tunnel fires. According to the records in Science Citation Index Expanded database in the Web of Science Core Collection, a total of 1073 articles or reviews related to pool fires have been published from 1966 to 2019. In order to have a better understanding of knowledge structure of this topic and further identify its development history and currently popular concerns, a bibliometric analysis of pool fire research is conducted by means of visualization software VOSviewer and CiteSpace. This work visually provides a comprehensive overview of pool fire research in terms of annual publication output, source journals, productive countries/regions, authors and their cooperation network, subject terms, and reference co-citation analysis. The analysis provides networks of co-cited references, authors, countries, subject terms, and their respective clusters, indicating their ranking in contributions to the pool fire related publications. The results can be applied to enhance the understanding of pool fire research and support further work in this area.