Mobility of lowland stream Trichoptera under experimental habitat and flow conditions   总被引：1，自引：0，他引：1  

Piet F.M. Verdonschot  Anna A. Besse-LototskayaDorine B.M. Dekkers  Ralf C.M. Verdonschot 《Limnologica》2012,42(3):227-234

The species-specific mobility of six species of lowland stream Trichoptera was studied in flume experiments with different habitats and current flows. The test species were selected according to their occurrence along the environmental gradient from more natural towards highly disturbed sandy, lowland streams of the North-West European plain. Two groups of species were distinguished, three species occurring more frequently towards the natural end versus three occurring more frequently towards the disturbed end of the stream disturbance gradient. Experiments were conducted in a temperature and light controlled environment in indoor, re-circulating, man-made stream channels with four replicate gutters each. The bottom of each gutter held ten trays filled with five selected habitat materials (two trays each), which provided refugia and food. Three flow treatments with constant current velocities of 10, 30, or 50 cm/s were applied. Movements were scored based on visual observations of the position of each individual at fixed time points. The first day after release, individuals moved around very actively; this ‘release effect’ was removed from further analyses. The trichopteran species occurring near the more natural end of the disturbance gradient exhibited significantly less mobility (on average 10-15% of individuals actively moved around) than the species from the more disturbed end of the gradient (on average 30-40% of individuals actively moved around). The first group of trichopteran species also spent significantly longer times in the leaves habitat compared to the other three species, which moved more or less independent of habitat. With increasing current velocity, all test species moved more frequently, particularly the species from the more disturbed end of the gradient. This could indicate behavior to avoid dislodgement. The mobility of all species exceeded the mobility needed to use habitat resources of food and shelter, both present in excess. Therefore, short-term movement could also be (partly) a random behavior. Overall, the more tolerant species from the disturbed end of the gradient showed more mobility and flexibility than the species occurring under more or less natural stream conditions. This was consistent with the hypothesis that mobility is an adaptation of tolerant, ubiquitous species. Mobility is an adaptation of r-strategists.  相似文献   

构造应力场与煤及瓦斯突出的关系   总被引：1，自引：0，他引：1  

程军  张丽红  吴国代  刘敬青  刘梓萱 《煤田地质与勘探》2012,40(4):1-4,11

地质构造对煤与瓦斯突出具有明显的控制作用,以往多是定性的分析和统计研究。通过构造应力场理论及相似模拟实验,分析了构造应力场与煤及瓦斯突出的关系。对相似实验结果进行对比分析,结合煤及瓦斯突出与褶曲构造展布关系实例,研究了褶曲构造不同部位应力分布特征及其对瓦斯突出的控制作用。结果显示:背斜翼部挤压区和转折区是煤及瓦斯突出的最危险地带;背斜轴部区一般不会出现严重的煤及瓦斯突出。   相似文献   

ATOVS 不同卫星资料在台风模拟中的同化试验研究   总被引：5，自引：1，他引：4  

李兴武  董海萍  郭卫东  高太长 《热带气象学报》2012,(2):157-166

利用美国国家大气研究中心(NCAR)开发的中尺度模式WRF(ARW)V3.2 及其三维变分同化系统WRF-3DVAR,以1011 号超强台风“ 凡亚比” 为个例,采用连续循环同化的方法对ATOVS 卫星资料进行同化试验,探讨了同化ATOVS 不同卫星资料对“ 凡亚比” 模拟的影响。结果表明,强度影响方面:同化ATOVS不同资料均可有效改善台风强度,台风中心海平面气压平均偏差从42 hPa 下降到18 hPa,但不同资料间的差异并不显著,平均在6 hPa 以内,这表明仅同化ATOVS 资料对台风强度的改善相对有限。路径影响方面:(1)不同卫星的同一种传感器资料效果略有不同,同化NOAA-18 和NOAA-15 的AMSU-A 资料效果较好,NOAA-16 的AMSU-A 效果较差;同化NOAA-15 和NOAA-16 的AMSU-B 资料效果相当,且均优于AMSU-A 资料。(2) 同一颗卫星不同传感器资料的差异较大,同化AMSU-B 资料的改善较为明显,HIRS-3 次之,AMSU-A较差,而同时同化不同资料并没有带来更为明显的改善。(3) 同时同化多颗卫星ATOVS 资料的试验表明,将多种资料引入到同化系统的同时,也带来相应的累积误差,因而仅同化一颗卫星可能比同时同化两颗或三颗卫星ATOVS 资料的效果要好。   相似文献   

侧向应力扰动对断层摩擦影响的实验研究   总被引：4，自引：0，他引：4       下载免费PDF全文

崔永权  马胜利  刘力强 《地震地质》2005,27(4):645-652

利用双向伺服控制装置,对含有与最大主压应力σ1呈45°夹角的预切面的花岗闪长岩标本进行了摩擦实验,结果表明,在σ1方向位移速率恒定、侧向应力σ2恒定的条件下,粘滑间隔随滑动面上正应力的增加而增加,粘滑应力降也随滑动面上正应力的增加而呈线性增加。但当σ2叠加了高频小振幅的正弦波扰动时,这种相关性发生了明显的变化,应力降大小和粘滑间隔的离散度均显著提高,特别是应力降可能会大幅度增加。与σ1扰动的实验结果相比,σ2扰动对断层粘滑的影响更为显著,这主要归因于正应力变化使滑动面的非均匀性加剧  相似文献   

多级多层复合滑坡工程病害的试验研究   总被引：2，自引：1，他引：1  

杨涛  周德培  周应华  邓宏艳 《工程地质学报》2005,13(3):325-329

张家坪滑坡具有多级多层的复杂滑体结构,本文选取最典型的断面开展了大型地质力学模型试验,模拟了边坡的开挖过程,并采用均匀毛细浸润技术研究雨水作用下的坡体稳定性,通过有无支挡的两阶段试验对比,分析了多级多层复合滑坡的变形失稳机制和工程病害,以及相应抗滑支挡结构的加固效果。  相似文献   

库车坳陷克拉2气田超压成因研究   总被引：3，自引：0，他引：3  

张洪  庞雄奇  姜振学 《地球学报》2005,26(2):163-168

物理实验模拟是研究油气运移和聚集的重要手段和方法。而天然气物理模拟实验则是一个研究相对不足而又非常重要的领域,它的操作和完善可以大大促进中国西部天然气勘探,直接影响着西气东输的国策。本文正是涉及这个领域,选取库车坳陷克拉2气田作为研究对象,模拟了其成藏模式,对其超压的特性进行了研究,认为构造挤压和充气增压是引起克拉2气田超压的主要原因,而充气增压的具体机制则是多级补给,也就是下部的冲起构造作为供源为上部的克拉2构造供气,促使其丰度和压力都升高。  相似文献   

长江口外颗粒有机碳及光合色素在不同溶氧水平下早期降解速率研究   总被引：1，自引：1，他引：0  

朱卓毅  张经  吴莹  张莹莹  林晶  季倩 《海洋与湖沼》2013,44(1):1-8

有机质降解是低氧形成的重要原因.长江口外的低氧近几十年来日趋恶化,引起了大量学者关注,但现场有机质降解及相关的耗氧速率还鲜见报道.本研究通过人工控制体系溶氧(DO)水平,于2006年10月在曾经出现低氧的长江口外近海进行现场有机质降解培养实验,以模拟有机质在沉降进入近底层水后早期(9天)内的生物地球化学过程,估算有机碳降解速率和耗氧速率.培养实验表明,有机质在几天内即可出现明显的降解,并伴随体系pH的下降和细菌、病毒的增加.体系溶氧对有机碳(POC)降解速率影响较大,POC在DO＞95％条件下的降解速率是DO＜50％条件下的5倍,分别为1.5 mmol/(m3·d)和0.3 mmol/(m3·d).光合色素岩藻黄素(FUCO)和叶绿素a(Chla)含量在9天内呈指数下降,其中80％的FUCO在9天内发生了降解.指数方程能较好地实现对观测数据的拟合,结果表明Chl a的半衰期为3-4天.不同溶氧条件下的结果表明低溶氧条件(DO＜50％)下浮游植物更容易成为降解有机质的来源.根据POC降解速率估算得到长江口外溶氧消耗速率分别为82-91 mmol/(m2·d)(DO＞95％条件)和27-30 mmol/(m2·d)(DO＜50％条件),远高于深海氧通量和表层50 m南海的氧消耗通量;以此耗氧速率为基础,估算得到长江口外层化形成至发育出低氧的时间为50-150天.  相似文献   

An oil slick spectral experiment of nearshore sea water in the East China Sea     

WANG Difeng  PAN Delu  GONG Fang  WANG Tianyu  ZHAN Yuanzeng 《海洋学报(英文版)》2013,32(11):34-40

Along with the rapid advance in global industrialization, oil spill events caused by offshore operations, trans- portation and accidents are increasing. Compared with ship surveys, monitoring oil spills through remote sensing has real-time, comprehensive, low-cost advantages, which can effectively guide cleaning and evalu- ation, and reduce the marine ecological destruction resulting from oil spills. Therefore, studying the remote sensing mechanism used to monitor marine oil spills is of great significance for ecological environmen- tal protection. This paper describes an experiment and corresponding analysis based on the above-water method, using the East China Sea coastal turbid water. The analysis shows that ＂upward short-wave＂ in ultraviolet and blue-purple bands and its displacement, along with the changing thickness, are important characteristics for distinguishing between the oil slick and the sea water, and also to differentiate oil slicks of different thicknesses. From blue to near-infrared bands, the spectrum of lube oil is flatter than that of diesel, and the diesel spectrum rises faster than the lube spectrum on the right side of the trough at 400 nm. These two features form an important basis for differentiating diesel from lube oil. These analyses will further the development of oil spill remote sensing in the East China Sea.  相似文献   

淡水和海水环境下沉积物搬运过程碳释放通量的模拟研究     

彭峰  唐梅  刘昱恒 《海洋科学》2013,37(9):77-81

基于室内物理模拟实验, 对长江沉积物进行淡水和海水环境下沉积物搬运过程碳释放通量实验模拟。结果表明, 模拟实验初期, 淡水和海水均为大气CO₂的源, 但淡水CO₂释放通量略高于海水;淡水、海水两种环境下, CH₄释放通量均较小, 为弱释放-弱吸收过程。对两种环境下碳通量对比研究发现,Eh 值可能是造成淡水和海水环境下CO₂通量差别的主要原因, 而pH 值可能对CO₂通量差别的影响较小。两种环境下温室气体通量差别的具体原因仍需进一步研究。通过模拟对比试验, 旨在为系统地认识长江流域水库的温室效应与减排提供科学依据, 为我国清洁水电能源发展提供理论参考。  相似文献   

大容量舱容积计量的快速测量新方法     

时永鹏  胡铁牛 《海洋工程》2013,31(5):89-95

针对不断大型化和多样化的船舶与海洋结构物舱室,为适应其舱容测量需求,借鉴传统的容量比较法和几何测量法,提出了一种新的高效、准确、适用性强的舱容测量方法。新测量方法采用间接积分计算舱容思路,包含实验与计算两个部分;实验中标准容器注水和未知体积大量注水交替进行,再将实验数据转化为可以描述舱容变化趋势的水线面积数据;计算部分基于水线面积数据、采用收敛性较好的样条插值方法得到近似水线面积曲线,并进一步积分得到测量舱容曲线。通过算例验证,相对于传统测量方法,该方法可以更方便、高效地完成大容量舱的容积测量,同时具有很高精度;并可根据舱体特点灵活安排测量方案,更好地解决测量效率与精度间的矛盾。  相似文献