Ecology of Diloma nov Aezelandiae at Portobello,New Zealand     

Sheila J. Logan 《新西兰海洋与淡水研究杂志》2013,47(4):699-714

Some aspects of the biology of Diloma (Fractarmilla) novaezelandiae (Anton) (= Zediloma subrostrata), a soft‐shore trochid gastropod, were investigated in Latham Bay, Portobello, South Island, New Zealand (45° 50’ 25” S, 170° 38’ 30” E). The distribution of D. novaezelandiae during September 1973 to June 1974 was recorded along three transects; pebble distribution, macroalgal cover, grain‐size distribution and organic carbon content in the sediment, range of water salinity, and length of time of exposure to air were also recorded along the transects.

The greatest population density of D. novaezelandiae occurred between 0.8 m and 1.4 m above Chart Datum. The trochid was found to prefer a hard substratum to a soft substratum, and there was a positive correlation of organic content of the sediment with density of D. novaezelandiae. As the population density decreased towards low water the individual shell size increased. Size: weight relationships were calculated and the results showed that dry flesh weight and dry shell weight were both proportional to the cube of the shell diameter.  相似文献   

板格形导管架桩基码头稳定性简化计算方法     

张连丽  王元战  陈飞 《海洋工程》2013,31(5):96-102

板格形导管架桩基码头是适用于深水域软土地基的新型港口与海岸工程结构。该结构由预制的板格形导管架及桩基构成,承载特性和破坏模式复杂。假定码头结构发生倾覆失稳时,转动点位于前桩轴线上,且距导管架底面距离为L。除结构的自身重量外,综合考虑板格形导管架与周围土体间的摩擦力、桩侧摩阻力、桩侧水平土抗力等,对结构进行极限状态受力分析,建立基于假想支撑点的稳定性分析模型,并通过强度折减法进行计算,求取安全系数。以天津滨海沿岸水文地质条件为背景,利用ABAQUS有限元分析软件,建立板格形导管架桩基码头三维弹塑性有限元模型进行稳定性分析,并与简化方法进行比较。结果表明,通过简化计算方法得到的安全系数与有限元结果较为吻合。  相似文献   

低屈服点钢剪切板阻尼器滞回性能试验研究   总被引：4，自引：0，他引：4  

宋中霜  ;李冀龙  ;韩露  ;李惠  ;欧进萍 《地震学刊》2014,(3):289-295

为改善传统滞变型阻尼器在小振动变形时不明显的耗能效果,利用国产低屈服点钢设计了5个剪切板阻尼器（LYPSSP）,并对其进行低周往复循环荷载试验,重点考察阻尼器核心板连接方式、高厚比、十字加劲肋对其滞回性能的影响。研究结果表明：核心板与翼缘板通过熔透焊缝连接与螺栓连接相比,构造简单、可靠度高且易加工;由国产低屈服点钢制作的剪切板阻尼器滞回曲线饱满,耗能性能好,在同一位移级别下循环的滞回曲线基本上重合,稳定性好,并且在整个循环加载过程中,强化现象非常明显,破坏之前也没有出现强度和刚度的突然改变;以P/Py为设计目标时,核心板高厚比越小、面外屈曲越小,滞回曲线就越饱满,耗能性能就越好;根据等效粘滞阻尼器系数和平均耗能指数,能够对阻尼器的耗能性能很好地做出评价。  相似文献   

Modeling the Effects of Heterogeneity and Anisotropy on the Excavation Damaged/Disturbed Zone (EDZ)   总被引：2，自引：0，他引：2  

S. H. Wang  C. I. Lee  P. G. Ranjith  C. A. Tang 《Rock Mechanics and Rock Engineering》2009,42(2):229-258

Summary  When modeling the mechanical behavior of underground excavations, it is necessary to include the influence of the rock mass characteristics on the Excavation Damaged/Disturbed Zone (EDZ). In this paper, the Realistic Failure Process Analysis code, RFPA, is used to model the extent of the EDZ. The inhomogeneous characteristics of rock at the mesoscopic level are included by assuming that the material properties of the constituent elements conform to a Weibull distribution; the anisotropy is incorporated as a transversely isotropic medium; the non-elastic characteristic is simulated via an elastic damage-based constitutive law. A finite element program is adopted as the basic stress analysis tool. In this study, a notable feature is that no a priori assumptions need to be made about where and how fracture and failure will occur – cracking can take place spontaneously and can exhibit a variety of mechanisms when certain local stress conditions are met. The deformation and failure process of anisotropic rock around excavations of different geometries is analyzed, and compared to experimental tests, showing similar fracture patterns. Additionally, the effect of confining stress and of different material layers is modeled and discussed. It is found that the model clearly illustrates that fracturing, both initiation and propagation, occurs as a combination of the stress concentrations and weakness planes introduced via the transverse anisotropy – which could represent either foliations or ubiquitous joint sets. Correspondence: Dr. Shuhong Wang, Box 265, School of Resource and Civil Engineering, Northeastern University, Shenyang 110004, P.R. China  相似文献   

环境管制对广东省污染产业转移的影响     

沈静  黄双双 《热带地理》2015,35(5):745-752

以广东省为研究对象,首先分析其2000―2010年污染产业转移的变化特征,发现从2006年开始出现由珠三角向非珠三角地区转移的趋势,其中粤北山区接受转移最多,转移趋势明显的行业包括采掘业、非金属制品业,而水电煤气供应业、有色金属行业有轻微的转移趋势。然后采用面板数据模型进行实证研究,以单位工业总产值的SO2排放量为环境管制因子,结果发现总污染产业、采掘业、非金属制品业、水电煤气供应业等产业转移与宽松的环境管制相关。环境管制对广东省污染产业转移起重要作用,中国地方政府强制性的“命令―控制式”的环境管制手段对产业转移的影响大。  相似文献   

Flow around circular and noncircular cylinders by a low-order panel method     

Iskender Sahin  Noriaki Okita 《Ocean Engineering》1998,25(7):529-539

Time-dependent cross-flow was studied around cylinders with circular and noncircular cross-sections. The numerical approach for the analysis was a low-order panel method based on constant source and dipole values along each panel. The method was previously used successfully for several applications, such as calculation of the added mass and damping coefficients. In simulating the viscous time-dependent flow around the cylinder, the time-dependent wake feature of the code was used. For the circular and D-cylinders, the results agreed well with the experiments. Suggestions for improving the results for T-cylinders with angle of attack are included.  相似文献   

柔性仿金枪鱼月牙形尾鳍水动力分析     

成巍苏玉民  秦再白徐玉如 《海洋工程》2004,22(4):73-79

为研究鱼类高速游动机理,以金枪鱼月牙形尾鳍为对象,采用面元法计算分析了其非定常水动力性能。假设尾鳍在横移和摇摆的同时,以某一匀速向前运动,并假设其在弦向和展向以某一给定规律发生变形,以模仿柔性变形。探讨了前进速度、横移和摇摆的幅度、频率及其相位差对柔性尾鳍推进性能的影响,并与做相应运动的刚性尾鳍进行了对比。  相似文献   

基于非定常面元法的海上浮式风机气动性能研究     

刘利琴  陈迪郁  沈文君  李昊  邓万如 《海洋工程》2021,39(5):16-27

对于海上浮式风机而言,由于受到剪切风、塔影效应、浮式基础运动等因素的共同影响,其气动载荷会更加复杂,因此如何准确快速地对海上风力机的气动性能进行预估显得尤为重要。基于速度势的非定常面元法理论,研究海上浮式风机气动载荷特性,编制了相关的计算程序。以NREL 5 MW风机为例,建立了叶片和尾流的三维数值模型,计算得到了不同风速下风机的输出功率以及叶片表面的压力分布,对比数据结果分析了该方法的可靠性。针对非定常流动,模拟了剪切风和塔影效应的作用,并重点分析了浮式基础运动对风机气动载荷的影响。研究表明,浮式基础的纵荡和纵摇会增加输出功率的波动幅值,艏摇运动会导致单个叶片上的气动载荷产生较大的波动,为浮式风机叶片控制提供了参考。  相似文献   

大型天线面板无接触测量系统     

刘波  段定乾 《测绘学院学报》1998,(2)

介绍了精密无接触三维测量系统 ,并用该系统对高精度反射面板进行多次测量 ,其检测精度均优于± 3 0 μm。该系统为高精度反射面板及其大型构件的型面检测和结构拼装提供了一条新途径。  相似文献   

基于DEA-Malmquist-Tobit模型的中国海洋渔业补贴财政效率及影响因素研究     

郑慧  高凡  赵昕 《海洋通报》2020,39(1):61-69

作为世界上最大的渔业生产国和贸易国,中国渔业补贴政策的制定和实施对国计民生具有重大意义,也是推进海洋强国战略建设的题中应有之义。本文选取基于规模报酬可变假设的DEA模型测算了中国海洋渔业补贴的效率水平,进一步利用Malmquist指数对补贴效率的动态变化进行分解,探究效率变化的内在驱动因素,然后建立分析补贴效率影响因素的面板Tobit模型,对补贴投入和环境变量对补贴效率的影响进行分析,结果表明,当前我国海洋渔业补贴效率整体较低,且全要素生产率呈下降趋势,最后基于实证结果从改善补贴规模和调整产业结构等方面提出改善渔业补贴效率的对策建议。  相似文献