Observations of Hector's dolphins (Cephalorhynchus hectori) associating with inshore fishing trawlers at Banks Peninsula,New Zealand

Fishing activities have the potential to alter the behaviour of cetaceans and pose a threat through bycatch. We present observations concerning the influence of inshore trawling on group size and behaviour of Hector's dolphins (Cephalorhynchus hectori) at Banks Peninsula, New Zealand, made during photo‐ID surveys from 2003 to 2007. Aggregations of dolphins, typically involved in what we assumed to be foraging behaviour, were observed following small inshore trawlers year‐round. Group size was larger for aggregations of dolphins following trawlers (mean ± SE = 22.9 ± 1.3, n = 83) than for non‐trawler groups (3.7 ± 0.2, n = 439), and dolphins were typically in a more “excited” state, frequently exhibiting aerial and sexual behaviours. We suggest that trawlers increase the availability of prey for Hector's dolphins and hence foraging behind trawlers is an energetically favourable activity. However, following trawlers probably also increases the risk of being caught in trawl nets, compounding the threats faced by this endangered species.     

Paradigms for planktonic assemblages: 50 years of contributions from the Leigh Marine Laboratory,Northland, New Zealand

Abstract

Plankton includes the primary producers and consumers that are critical for healthy ecosystem function in the marine realm. My objective was to identify the major contributions of the Leigh Marine Laboratory to our broader understanding of planktonic assemblages. Significant contributions were made prior to 1990 on the ecology of larval fishes. From the 1990s the focus changed to the sensory biology of larval invertebrates and fishes, with a strong emphasis given to the role of reef sound in attracting potential settlers. Both early and post 1980s research has been highly influential in a paradigm shift away from passively drifting larvae that have little control over their fate. Important contributions have also been made on the dynamics of nutrient–phytoplankton interactions, larval development and aquaculture. Opportunities abound for future research on the dynamics of planktonic assemblages in shelf waters and in changing seas.     

Effect of degree of saturation on mechanical behaviour of unsaturated soils and its elastoplastic simulation

The two stress-state variable approach has been widely used in interpreting unsaturated soil behaviour. However this approach cannot take into account the effect of degree of saturation or water contents on the stress–strain behaviour and strength of unsaturated soils. The triaxial test results presented in this paper show that even if the same path of net stress and suction is followed, the stress–strain relation and strength are different due to different degrees of saturation. When other conditions are the same, the higher the degree of saturation for the soil sample is, the higher the stress ratio corresponding to a given axial strain will be. This effect can be modeled by using an elasto-plastic constitutive model coupling hydraulic and mechanical behaviour of unsaturated soils. Comparisons between the predicted and measured results are presented, which demonstrate that the model can quantitatively simulate the influence of the degree of saturation on stress–strain behaviour and strength of unsaturated soils.     

Determination of the crop row orientations from Formosat-2 multi-temporal and panchromatic images

This paper presents a technique developed for the retrieval of the orientation of crop rows, over anthropic lands dedicated to agriculture in order to further improve estimate of crop production and soil erosion management. Five crop types are considered: wheat, barley, rapeseed, sunflower, corn and hemp. The study is part of the multi-sensor crop-monitoring experiment, conducted in 2010 throughout the agricultural season (MCM’10) over an area located in southwestern France, near Toulouse. The proposed methodology is based on the use of satellite images acquired by Formosat-2, at high spatial resolution in panchromatic and multispectral modes (with spatial resolution of 2 and 8 m, respectively). Orientations are derived and evaluated for each image and for each plot, using directional spatial filters (45° and 135°) and mathematical morphology algorithms. “Single-date” and “multi-temporal” approaches are considered. The single-date analyses confirm the good performances of the proposed method, but emphasize the limitation of the approach for estimating the crop row orientation over the whole landscape with only one date. The multi-date analyses allow (1) determining the most suitable agricultural period for the detection of the row orientations, and (2) extending the estimation to the entire footprint of the study area. For the winter crops (wheat, barley and rapeseed), best results are obtained with images acquired just after harvest, when surfaces are covered by stubbles or during the period of deep tillage (0.27 > R² > 0.99 and 7.15° > RMSE > 43.02°). For the summer crops (sunflower, corn and hemp), results are strongly crop and date dependents (0 > R² > 0.96, 10.22° > RMSE > 80°), with a well-marked impact of flowering, irrigation equipment and/or maximum crop development. Last, the extent of the method to the whole studied zone allows mapping 90% of the crop row orientations (more than 45,000 ha) with an error inferior to 40°, associated to a confidence index ranging from 1 to 5 for each agricultural plot.     

Politics eclipses climate extremes for climate change perceptions

Whether or not actual shifts in climate influence public perceptions of climate change remains an open question, one with important implications for societal response to climate change. We use the most comprehensive public opinion survey data on climate change available for the US to examine effects of annual and seasonal climate variation. Our results show that political orientation has the most important effect in shaping public perceptions about the timing and seriousness of climate change. Objective climatic conditions do not influence Americans’ perceptions of the timing of climate change and only have a negligible effect on perceptions about the seriousness of climate change. These results suggest that further changes in climatic conditions are unlikely to produce noticeable shifts in Americans’ climate change perceptions.     

地质导向技术在煤层气水平井中的应用——以柳林区块某多分支水平井为例

地质导向技术能有效提高煤层气水平井施工成功率和煤层钻遇率,但由于其具有导向参数多、工艺要求高、易受地质因素影响等特点,使其在实际应用中还存在诸多难点。以柳林区块内某多分支水平井为例,针对该井现场地质导向作业面临的资料缺乏、参数受欠平衡钻进干扰、煤层结构复杂等难点,建立合适的地质导向模型,优选合理的导向参数和导向系统,对地质导向技术在实际应用中的工艺与流程进行了系统论述。实践表明,地质导向技术在该井的应用效果良好:煤层钻遇率达到了93.1%;截至目前,该井的产气量达8600m3/d,且还在进一步提升。     

Pore orientation of granular materials during biaxial compression

The local pore spaces in granular materials tend to be aligned parallel to the major principal stress direction upon particle mobilization. Manifestation of this response has been numerically validated in our previous studies with the aid of discrete element method modeling and image processing techniques during creep and shearing. We now extend the modeling of pore geometry, constructed with spherical particles, to assemblies of particle clumps. Two-dimensional simulations are performed for both loose and dense assemblies of spherical particles and particle clumps. Each particle packing is bound by rigid or flexible walls and subjected to biaxial compression and the particle mobilization effect on the evolution of pore orientation is explored. Randomly shaped pores surrounded by adjacent particles are geometrically quantified by Delaunay tessellation and fitted with ellipses. Results show that localization is apparent in dense assemblies, in particular for clumped particle packing, while loose assemblies exhibit diffusive failure. Small pores within well-defined shear bands tend to align either parallel to the direction of the shear band or perpendicular to the major principal stress. On the other hand, small pores within the blocks and large pores have a tendency to become elongate towards the major principal stress direction. This study reveals for the first time that pore orientation is dependent upon particle shape, pore size, and assembly conditions on the pore and global scales.     

极化方位角补偿信息支持下的植被参数反演

SAR图像中散射目标的散射矩阵受极化方位角(POA)的影响会改变散射体的散射特性,散射矩阵是极化干涉SAR (PolInSAR)估计不同极化状态下复相干性的基础。本文根据极化方位角产生机制,建立了多视情况下基于极化方位角补偿的极化干涉相干性估计模型,分析了极化方位角补偿对相干性估计方法和不同散射机制下相干性估计的影响程度,研究了基于三阶段法与极化方位角补偿的植被参数反演。利用L波段SIRC全极化SAR图像为实验数据验证极化方位角补偿对极化干涉相干性估计和植被参数反演的可行性。实验结果表明,极化方位角补偿能够改变不同极化状态相干性分布规律,提高相干直线拟合精度,改善植被参数反演的可靠性和合理性。     

A virtual experiment technique on the elementary behaviour of granular materials with discrete element method

Multi‐scale investigations aided by the discrete element method (DEM) play a vital role for current state‐of‐the‐art research on the elementary behaviour of granular materials. Similar to laboratory tests, there are three important aspects to be considered carefully, which are the proper stress/strain definition and measurement, the application of target loading paths and the designed experiment setup, to be addressed in the present paper. Considering the volume sensitive characteristics of granular materials, in the proposed technique, the deformation of the tested specimen is controlled and measured by deformation gradient tensor involving both the undeformed configuration and the current configuration. Definitions of Biot strain and Cauchy stress are adopted. The expressions of them in terms of contact forces and particle displacements, respectively, are derived. The boundary of the tested specimen consists of rigid massless planar units. It is suggested that the representative element uses a convex polyhedral (polygonal) shape to minimize possible boundary arching effects. General loading paths are described by directly specifying the changes in the stress/strain invariants or directions. Loading can be applied in the strain‐controlled mode by specifying the translations and rotations of the boundary units, or in the stress‐controlled mode by using a servo‐control mechanism, or in the combination of the two methods to realize mixed boundary conditions. Taking the simulation results as the natural consequences originated from a complex system, virtual experiments provide particle‐scale information database to conduct multi‐scale investigations for better understanding in granular material behaviours and possible development of the constitutive theories provided the qualitative similarity between the simulation results from virtual experiments and observations on real material behaviour. Copyright © 2011 John Wiley & Sons, Ltd.     

IMU/DGPS数据在1∶50000 DOM生产中的应用

IMU/DGPS(惯导测量仪/差分全球定位系统)技术航测成图法可直接获取外方位元素,缩短航测成图周期,降低航测成本。通过相应的试验及具体生产的实施,阐明利用该技术获取的控制数据进行1∶50000DOM制作的技术流程及作业过程中出现问题的处理方法。