取土器几何尺寸对饱和软黏土样结构的扰动研究          下载免费PDF全文

李志杰  宋晶  张鹏  赵洲  黄坚森  杨守颖 《地质科技通报》2019,38(6):17

基于颗粒流软件模拟,以吹填淤泥为例,分析了取土器的内径、切角、壁厚等尺寸参数对高黏性软土微观 动力学特性的影响;通过分层方法,比较了７组土样层间颗粒特征拐点的运动行为.模拟结果表明:土样的颗粒 在底部形成对流λ移场,对流处上方颗粒主要受拉膨胀,对流处下方颗粒主要受压收缩,由此造成孔隙率的规律 变化和层理的弯曲变形.７组参数对应土样的孔隙率曲线与初始孔隙率曲线的交点同颗粒λ移场的对流λ置存 在协同关系.土样层理表现为向下弯曲变形,层间颗粒λ移行为存在特征拐点,拐点之间颗粒扰动行为不明显; 反之,颗粒扰动行为较大,这种变形特征可拟合为下开口的旋转抛物面,且曲面方程的曲面形状拟合系数a 值能 初步评估７组土样的扰动程度.层间特征拐点的连线可再拟合为旋转抛物面,抛物面体积与土样体积的比值可 用来评估土样的原状性.   相似文献   

倒置显微镜拍照法对浮游植物计数的稳定性分析     

陈明华  史康佳  李志杰  蔡菲  张浩  张建辉  胡文涛 《湖泊科学》2020,32(5):1564-1574

准确定量分析湖泊河流中浮游植物群落结构对评价湖泊河流健康和保障人类饮水安全至关重要.显微镜镜检法是定量分析浮游植物群落结构的唯一方法,但不能满足浮游植物计数分析要求.在Utermhl倒置计数管视野法基础上提出倒置显微镜拍照法,使用拍照法对小球藻、四尾栅藻、斜生栅藻3种纯藻样品和鄱阳湖野外样品计数得到:1)在5、10倍物镜下拍照因浮游植物个体太小导致计数不准确,在20、40倍物镜下拍照计数准确,增加拍照次数可较好地避免计数偏差,拍照次数是影响拍照法计数分析的主要因素; 2)小球藻、四尾栅藻、斜生栅藻在20和40倍物镜下分别拍摄5和10张照片时每升浮游植物计数稳定;鄱阳湖野外样品在20和40物镜倍下分别拍摄5、10张照片时每升浮游植物计数稳定; 3)倒置显微镜拍照法比计数框行格法、目镜视野法、目镜行格法和Utermhl倒置计数管视野法计数稳定,变异系数最小为0.812.  相似文献   

风和径流量对长江口缺氧影响的数值模拟   总被引：1，自引：1，他引：0  

郑静静  刘桂梅  高姗  李云  李志杰 《海洋学报》2018,40(9):1-17

受自然和人类活动的影响，海洋缺氧现象日益严重，威胁着海洋生态环境，海洋缺氧问题已经引起了人们的广泛关注。本文应用区域海洋模式并耦合生态模式，对东海的生态系统进行了数值模拟和分析研究。与观测数据比较显示，该模型能较好地模拟长江口外生态变量的分布趋势。另外本文通过设置不同敏感性实验，探讨风和径流量对长江口底层缺氧现象的影响，结果分析表明，风和径流量对长江口外缺氧区的形成有显著的影响。径流量变化虽然对长江口外缺氧区的季节变化影响并不显著，但是对缺氧区域面积却存在显著的影响。径流量增加，水体层化增强，表层叶绿素浓度增加，最终导致缺氧区域范围扩展；径流量减小，水体层化减弱，表层叶绿素浓度减小，缺氧区域范围缩小。风向和风速的改变不仅影响长江口外缺氧区的季节变化，还影响缺氧区域面积。  相似文献   

Effects of probiotic on microfloral structure of live feed used in larval breeding of turbot Scophthalmus maximus     

姜燕  张正  王印庚  景亚运  廖梅杰  荣小军  李彬  陈贵平  张和森 《中国海洋湖沼学报》2018,(3)

The effects of an exogenous probiotic( Bacillus amyloliquefaciens) on microbial community structure of B ranchionus plicatils and A rtemia sinica were evaluated in this study during turbot( Scophthalmus maximus) larval breeding. The analysis and comparison of the microfloral composition of live feed with probiotic was conducted using the Illumina HiSeq PE250. The abundance of microbial species and diversity of microflora in live feed with B. amyloliquefaciens were higher than those in the control. The microfloral composition was similar among the three replicate experimental groups of B. plicatils compared with the control after enrichment. L actococcus, Pseudoalteromonas, and Alteromonas were always dominant. Additionally, some other bacterial species became dominant during the enrichment process. The microbial community during nutrient enrichment of A. sinica was rather similar among the three control replicates. Relative abundance of Cobetia sp., the most dominant species, was 54%–65.2%. Similarity in the microbial community was still high after adding B. amyloliquefaciens. Furthermore, P seudoalteromonas and Alteromonas replaced Cobetia as the dominant species, and the abundance of Cobetia decreased to 4.3%–25.3%. Mean common ratios at the operational taxonomic unit level were 50%–60% between the two B. plicatils and A. sinica treatments. Therefore, the microbial community structure changed after adding B. amyloliquefaciens during nutrient enrichment of B. plicatils or A. sinica and tended to stabilize. Additionally, the abundance of V ibrio in any kind of live feed was not significantly dif ferent from that in the control. These results will help improve the microflora of B. plicatils and A. sinica and can be used to understand the multiple-level transfer role of probiotic species among probiotic products, microflora of live feed, and fish larvae.  相似文献   

全球粮食安全格局的时空演化     

蔡建明  马恩朴  林静  廖柳文  韩燕 《地理学报(英文版)》2020,30(2):179-196

Food security is the primary prerequisite for achieving other Millennium Development Goals(MDGs).Given that the MDG of“halving the proportion of hungers by 2015”was not realized as scheduled,it will be more pressing and challenging to reach the goal of zero hunger by 2030.So there is high urgency to find the pattern and mechanism of global food security from the perspective of spatio-temporal evolution.In this paper,based on the analysis of database by using a multi-index evaluation method and radar map area model,the global food security level for 172 countries from 2000 to 2014 were assessed;and then spatial autocorrelation analysis was conducted to depict the spatial patterns and changing characteristics of global food security;then,multi-nonlinear regression methods were employed to identify the factors affecting the food security patterns.The results show:1)The global food security pattern can be summarized as“high-high aggregation,low-low aggregation”.The most secure countries are mainly distributed in Western Europe,North America,Oceania and parts of East Asia.The least secure countries are mainly distributed in sub-Saharan Africa,South Asia and West Asia,and parts of Southeast Asia.2)Europe and sub-Saharan Africa are hot and cold spots of the global food security pattern respectively,while in non-aggregation areas,Haiti,North Korea,Tajikistan and Afghanistan have long-historical food insecurity problems.3)The pattern of global food security is generally stable,but the internal fluctuations in the extremely insecure groups were significant.The countries with the highest food insecurity are also the countries with the most fluctuated levels of food security.4)The annual average temperature,per capita GDP,proportion of people accessible to clean water,political stability and non-violence levels are the main factors influencing the global food security pattern.Research shows that the status of global food security has improved since the year 2000,yet there are still many challenges such as unstable global food security and acute regional food security issues.It will be difficult to understand these differences from a single factor,especially the annual average temperature and annual precipitation.The abnormal performance of the above factors indicates that appropriate natural conditions alone do not absolutely guarantee food security,while the levels of agricultural development,the purchasing power of residents,regional accessibility,as well as political and economic stability have more direct influence.  相似文献   

考虑土参数自相关距离影响的单桩可靠性设计方法     

刘超  袁颖  左朝晖  宁志杰  周爱红 《水文地质工程地质》2020,47(3):122-127

在岩土工程设计中，准确地衡量土层参数的空间变异性决定了设计结构的可靠性和经济性，土参数的自相关距离是反映其空间变异性的一个重要指标。目前对于自相关距离与结构可靠性之间的关系的研究还很不完善。本文以单桩可靠性设计为例，选取工程场地的静力触探试验数据，引入随机场理论描述侧摩阻力和锥尖阻力的分布特征，利用递推平均法计算各地基土层侧摩阻力和锥尖阻力的自相关距离，在描述土层侧摩阻力和锥尖阻力的分布特征时考虑了自相关距离的影响，进一步结合蒙特卡洛法计算单桩的可靠指标。结果表明土参数取值考虑自相关距离的影响后，降低了土参数分布的离散程度，计算的单桩可靠指标更高。在保证桩基安全度的前提下，设计结果能够降低工程成本。  相似文献   

湖北武汉岩溶塌陷易发性评价          下载免费PDF全文

涂婧  刘长宪  姜超  郑晓明  熊志涛  廖明政  李海涛 《中国地质灾害与防治学报》2020,31(4):94-99

近年来,武汉市岩溶塌陷地质灾害时有发生,给城市建设和人民生命财产造成了一定的损失,严重制约了武汉市社会经济的发展。为了提出科学合理的岩溶塌陷地质灾害防治措施和保障城市化进程的顺利进行,开展岩溶塌陷易发性评价是一项十分重要的工作。本文在武汉市岩溶塌陷调查成果的基础上,采用层次分析法和综合指数法相结合,对武汉市主要城区的岩溶塌陷易发性进行了评价,为制定武汉市岩溶塌陷地质灾害防治措施奠定了坚实的基础。  相似文献   

海草床鱼类群落结构的时空变化及其在热带海草床中的育幼     

杜建国  王彦国  PERISTIWADY Teguh  廖建基  MAKATIPU Petrus Christianus  HUWAE Ricardo  鞠培龙  LOH Kar Hoe  陈彬 《海洋学报(英文版)》2018,37(12):63-72

本文以印尼北苏拉威西东部的潟湖为对象，研究了热带海草床鱼类群落的种类组成和时空变化。研究发现当地鱼类的香农-威纳指数在1.57-3.69之间多样性相对较高。在科水平，天竺鲷科的丰度（8.27 ind./（100 m²））和生物量（28.49 g/（100 m²））最高。在物种水平，侧带天竺鲷（Apogon lateralis）的丰度最高，环纹圆天竺鲷（Sphaeramia orbicularis）的生物量最大。对于物种的空间变化，潟湖湖顶、湖中和湖口首先聚类在一起，这可能是由于基质类型引起的。干季和湿季的鱼类种类、丰度和生物量均比转换季高，这可能是由较强的季风造成的，强季风为鱼类提供了更适宜的环境和食物。93.1%的鱼类的最大体长小于它们的性成熟体长，暗示了海草床是很多鱼类的育幼场。因此，保护海草床对渔业和资源的可持续利用至关重要。  相似文献   

海南儋州海域造礁石珊瑚种类组成及动态变化研究          下载免费PDF全文

廖宝林  肖宝华  覃业曼  谢子强  谢勇琪  朱鸣 《海洋开发与管理》2020,37(7):55-61

文章通过断面法调查分析了儋州海域海花岛沿岸、南华墟沿岸和磷枪石岛沿岸造礁石珊瑚的种类组成与群落分布，结果表明：儋州海域造礁石珊瑚共有12科25属55种，相较于此前的研究增加了10个种，优势种为斯氏角孔珊瑚、澄黄滨珊瑚、柱角孔珊瑚；活造礁石珊瑚覆盖率急剧下降，由2012年的42.92%下降至现在的22.24%，降幅高至48.18%；造礁石珊瑚死亡率高居不下，长期维持在35%左右；初级群落以团块状造礁石珊瑚为优势种的趋势愈发明显，且单一绝对优势种的情况频繁出现，说明该海域造礁石珊瑚群落受到了较为严重的破坏，导致群落退化演替，分析认为这种破坏是由自然因素和人为活动共同造成的。  相似文献   

基于ABAQUS的深水连接器连接性能分析     

曹博  蔡志杰  石中玉  张玉龙  段梦兰 《海洋工程》2020,38(3):132-139

为解决现有深水连接器连接性能研究中力学分析建模不准确,且缺乏抗弯抗扭能力分析的问题,基于ABAQUS有限元分析软件对深水连接器进行三维模型动态仿真分析,对连接器的受力、密封性能以及在实际工程需求中不同内压下的抗弯及抗扭性能进行深入研究。结果表明:在安装及生产两种工况下,深水连接器各部件除密封环外受力均满足其强度设计要求,密封环接触表面发生合理塑性变形,满足密封要求;随着内压的增加,深水连接器的抗弯能力逐渐下降,抗扭能力则呈现增加的趋势;极限弯矩分别在0 MPa与35 MPa内压下的判定依据为密封失效,在14 MPa与52 MPa内压下的判定依据为下毂座屈服,而极限扭矩在不同内压下的判定依据均为密封失效。  相似文献