Spatial distribution and sources identification of polycyclic aromatic hydrocarbons in Wolong Lake,Northeast China

The aquatic ecosystem maybe significantly affected by polycyclic aromatic hydrocarbons(PAHs) released from fresh water sediments. In order to protect biodiversity, the spatial distribution and sources of PAHs in the sediment of Wolong Lake in Northeast China were studied. A total of 17 surface sediment samples were collected and 12 PAHs were analyzed. The results were as follows. The concentration of total PAHs(TPAHs) ranged between 1412.9 μg/kg and 3948.3 μg/kg(dry weight). Indeno [1, 2, 3-c, d] pyrene was the dominant contaminant which accounted for 87%–98% of TPAHs. Diagnostic ratios of PAHs and principal component analysis showed that biomass combustion and vehicle emissions were likely to be the dominant sources of PAHs in the sediment. PAHs can be considered safe in the context of environmental and human health protection, based on the overall toxicity. Individual PAHs were positively correlated with total organic carbons. These results will be helpful to control PAHs and protect the aquatic ecosystem in the lake.     

整治工程影响下的河口拦门沙航道回淤特征及成因——以射阳港航道为例

通过不同时期实测地形资料,对比分析射阳港拦门沙航道一期整治工程建设后航道的回淤分布特征;利用实测水文泥沙资料和潮流数学模型计算分析射阳河口拦门沙航道开挖后的水流、含沙量特征;探讨了射阳港拦门沙航道淤积的泥沙来源和淤积成因。研究表明:航道开挖后沿程普遍淤积,尤其是口门及堤根区段航道淤积严重。导致航道淤积的主要原因为:有掩护航道内涨潮流速大、落潮流速小,口门外高含沙量水体进入航道后泥沙很难被带出航道,导致航道内普遍淤积;口门内2 km范围内回淤较大是由于越堤流输沙和口门内侧涨潮期间存在明显回流;导堤根部航道段回淤较大是由于射阳河与黄沙港河汇流后河道放宽,落潮期间出河口的水体挟沙力突然降低。     

土壤含水率对风沙流结构及风蚀量的影响

通过对科尔沁沙地典型生境(流动沙丘、沙质草地和农田)的土壤进行风洞试验,分析了不同含水率下3类土壤的风沙流结构、输沙率及总输沙量的变化趋势.结果表明:(1)不同含水率下,3类土壤的输沙率随高度的增加均呈现减小趋势,且有良好的指数函数关系.(2)随含水率的增加,流动沙丘和沙质草地土壤风沙流沙粒的平均跃移高度增加、0-12...     

1951—2020年广州地区极端气温指数年月尺度变化研究

根据广州国家基本气象站1951—2020年的逐日气温资料,采用线性趋势法、距平及累积距平法和Mann-Kendall检验法,对WMO推荐的16种极端气温指数中的13种以及2种结合本地实际的新的极端气温指数共计15种指数进行计算,从月尺度和年尺度分析广州地区各极端气温指数随时间变化的趋势和突变年份,并对以往研究中较少探究的基期的选择对相对极端气温指数的结果影响进行了对比分析。(1)从年尺度看,广州地区近70 a的夏日日数SU25、酷热日数SU35、热夜日数TR20、非常热夜日数TR26、最高气温TXx、最低气温TNn、最低气温最大值TNx、相对暖夜日数TN90p、暖昼日数TX90p、显著偏暖持续指数WSDI均呈现明显的上升趋势,相对冷夜日数TN10p、冷昼日数TX10p和偏冷持续指数CSDI呈现下降趋势,气温日较差DTR和最高气温最小值TXn变化趋势不明显;(2)新的极端气温指数SU35和TR26的上升速率明显大于SU25和TR20的上升速率,能更好地反映近70 a昼夜体感炎热日数呈现极显著的上升趋势,更加符合评估气候变化对当地生产生活的影响;(3)从月尺度来看近70 a广州地区的暖系列...     

沿海观测站海表温度质量控制和半日特征分析

Sea surface temperature(SST) data obtained from coastal stations in Jiangsu, China during 2010–2014 are quality controlled before analysis of their characteristic semidiurnal and seasonal cycles, including the correlation with the variation of the tide. Quality control of data includes the validation of extreme values and checking of hourly values based on temporally adjacent data points, with 0.15°C/h considered a suitable threshold for detecting abnormal values. The diurnal variation amplitude of the SST data is greater in spring and summer than in autumn and winter. The diurnal variation of SST has bimodal structure on most days, i.e., SST has a significant semidiurnal cycle. Moreover, the semidiurnal cycle of SST is negatively correlated with the tidal data from March to August, but positively correlated with the tidal data from October to January. Little correlation is detected in the remaining months because of the weak coastal–offshore SST gradients. The quality control and understanding of coastal SST data are particularly relevant with regard to the validation of indirect measurements such as satellitederived data.     

XLT-230型全液压旋喷履带钻机的设计

随着高压旋喷技术的发展,出现了新的双高压旋喷工艺即RJP工法,为了满足RJP工法施工的需求,设计研制了XLT-230型全液压旋喷履带钻机。该钻机操纵简单,满足RJP施工工艺,配套大扭矩、大通孔式动力头,具有间断提升、定向旋喷等功能,适合多种工程工况。详细论述了XLT-230型钻机的总体结构及技术参数、钻机主要部件的设计,介绍了整机的液压系统和电气系统。     

射阳港拦门沙航道整治工程建设前后水沙特征分析

为研究工程区海域水沙特征的时空分布、运动规律,采用不同时期的现场水文泥沙资料,对射阳港拦门沙航道工程建设前后的水流、含沙量、悬沙粒径和底质特征进行了对比分析。研究表明:射阳港一期航道工程建设后航道内潮波发生变形,涨潮流速大、历时短;落潮流速小、历时长,进入到航道内泥沙很难被带出航道,容易导致航道淤积。工程区海域整体含沙量较大,一期工程建设后导堤内涨潮含沙量明显增大,口门净输沙向口内,通过口门进入到航道的高含沙水体是航道淤积的重要沙源之一。导堤间边滩表层存在部分淤泥,且具有一定流动性,在水流及自身重力作用下,边滩淤泥可归入航道内。     

一种改进YOLOv4的遥感影像典型目标检测算法

如何使传统神经网络算法对遥感影像典型目标检测表现出良好的适应性是当前遥感领域的一项难点.在深入解析最新YOLOv4网络结构及算法核心思想前提下,首先通过增加104×104的特征层尺度并嵌入SE模块进行网络结构改进;继而根据待检测目标尺度特点调整锚点框,提高YOLOv4算法对遥感影像典型目标检测性能;最后设计对照实验进行...     

Stick–Slip and the Transition to Steady Sliding in a 2D Granular Medium and a Fixed Particle Lattice

We report an experimental study of the stick–slip to steady sliding behavior of a solid object pulled, via a spring, across 2D granular substrates of photoelastic disks that are either fixed in a solid lattice (granular solid) or unconstrained, forming a granular bed. We observe a progression of friction regimes with increasing sliding speed, including single-slip, double-slip, and mixed stick–slip regimes, steady sliding, and inertial oscillations. For the case of the granular bed, we report a detailed analysis of frictional behavior for the low speed stick–slip regime, including spring and elastic energy dependencies during the stick and slip portions of the motion. For the case of the granular solid, we explore friction in the presence and absence of externally applied vibrations, and compare it with sliding on a granular bed, which is intrinsically disordered. We observe that external vibration reduces transition values for both the single-slip to double-slip transition and the stick–slip to steady sliding transition. Moreover, we observe that the effect of packing disorder on granular friction seems similar to the effect of vibration-induced disorder, a result that, to our knowledge, has not been reported previously in the experimental literature.     

CFG桩在某大型油罐局部地基处理中的应用

通过工程实例,介绍CFG桩在大型油罐地基局部处理中,既有效提高软弱地基强度,又最大限度保持不同地基变形协调一致的处理方法.针对油罐体型的特殊性,采用了沿油罐圆心环形布桩,并且根据不同地段地基土性质的纵横向差异采用不等距布桩的方案.复合地基处理效果理想,达到了预期的设计目的,为类似工程的地基处理提供了一种新的设计理念,供类似工程参考.