Seagrass-Watch: Engaging Torres Strait Islanders in marine habitat monitoring

Involvement in scientifically structured habitat monitoring is a relatively new concept to the peoples of Torres Strait. The approach we used was to focus on awareness, and to build the capacity of groups to participate using Seagrass-Watch as the vehicle to provide education and training in monitoring marine ecosystems. The project successfully delivered quality scientifically rigorous baseline information on the seasonality of seagrasses in the Torres Strait—a first for this region.     

塔北哈拉哈塘地区奥陶系潜山岩溶储层发育特征及控制因素

哈拉哈塘地区奥陶系潜山岩溶缝洞型储层是哈拉哈塘油田的主力产层。通过对岩溶地质背景、区域构造分析,利用本区钻录井、薄片、岩芯等资料研究岩溶型储层特征,探讨储层分布规律及岩溶作用对储层的控制。结果表明哈拉哈塘地区奥陶系潜山岩溶储层的主体发育于一间房组和鹰山组。垂向上潜山区存在两套储层:上部表层岩溶带储层及下部径流溶蚀带储层。表层岩溶带储集类型主要为孔洞型和裂缝—孔洞型储层,主要受一间房组沉积末期的岩溶作用及桑塔木组沉积末期岩溶作用共同控制;径流溶蚀带储层类型主要为洞穴型、裂缝-孔洞型储层,岩溶缝洞系统以岩溶管道系统为主,储层形成受良里塔格期及桑塔木组沉积末期岩溶作用等多期岩溶作用控制。岩溶层组、岩溶作用期次、古地貌、古水系及断裂等控制了岩溶储层的分布发育,形成了复杂的缝洞体。      

上海城市建成环境对居民通勤方式选择的影响

伴随中国快速城市化与机动化进程,私人汽车拥有量不断增长,由此引起的交通拥堵和环境问题已成为制约中国城市可持续发展的难题。基于上海市区的居民通勤问卷调查数据,采用多项Logit模型检验了街道尺度城市建成环境对于居民通勤方式选择的影响,结果表明,在控制了其他因素后,提高居住地的人口密度、土地利用混合度与十字路口比重,可以减少小汽车通勤方式的选择,而就业地建成环境对居民通勤方式选择影响相对较弱;建成环境对通勤方式选择的影响会因个体的社会经济异质性而不同。这些结论为通过优化土地利用规划来优化居民通勤结构的城市交通和城市规划政策提供了启示。     

基于Hill稳定条件的条形锚板抗拔承载力研究

基于虚功原理的Hill稳定条件可较为明确地判定岩土材料的局部稳定性和整体稳定性：当地基系统的局部二阶功小于0时,材料点局部潜在失稳;当地基的整体二阶功小于0时,地基系统达到极限状态,整体潜在失稳。对ABAQUS进行了二次开发,使Hill稳定条件与有限元法相结合,求解胶结钙质土地基中条形锚板的抗拔承载力。研究结果表明,对于条形锚板在摩擦型岩土材料中的抗拔承载力问题,采用有限元方法结合Hill稳定条件,能较好地预测地基失稳范围和潜在失稳区域,失稳判据明确,易于确定极限荷载,并能较为准确地描述锚板的承载力系数及其随埋深的变化规律。利用有限元法结合Hill稳定条件求解承载力问题的思路和方法是有效和可行的,有明确的物理意义和力学理论基础,应用方便,值得进一步研究、推广并应用于较为复杂的岩土工程问题。     

层状岩体边坡动态稳定性拟静力上限分析

将强度折减技术与极限分析上限定理结合,利用安全系数Fs评定指标对层状岩体边坡进行稳定性上限分析,与已有研究成果进行了对比分析,并较为详细地分析了相关参数对层状岩体坡体安全系数和潜在破裂面的影响。分析结果表明,与同类计算方法的对比可以证明表明文中方法的正确性;边坡安全系数和破坏范围受边坡坡度、岩体重度、边坡高度、动载效应系数和岩层倾角的控制;当岩层倾角处于一定范围时,层状岩体边坡发生顺层失稳的可能性最大,工程中需特别注意。     

On the Use of Changes in Dihedral Angle to Decode Late-stage Textural Evolution in Cumulates

The melt-filled pore structure in the final stages of solidificationof cumulates must lie somewhere between the two end-membersof impingement (in which pore topology is controlled entirelyby the juxtaposition of growth faces of adjacent grains) andtextural equilibrium (in which pore topology is controlled bythe minimization of internal energies). The exact position betweenthese two end-members is controlled by the relative rates ofcrystal growth and textural equilibration. For samples in whichgrowth has stopped, or is very slow, textural equilibrium willprevail. A close examination of dihedral angles in natural examplesdemonstrates that these two end-member textures can be distinguished.The impingement end-member results in a population of apparentsolid–melt dihedral angles with a median of 60° anda standard deviation of 25–30°, whereas the texturallyequilibrated end-member population has a median of 28° anda standard deviation of 14°. For the specific case of cumulatesin the Rum Layered Intrusion, residual porosity in troctoliticcumulates was close to the impingement end-member, whereas thatin peridotites was close to melt-bearing textural equilibrium.Suites of glass-bearing samples from small, or frequently disturbed,magma systems show modification of initial impingement textures.These modifications may be a consequence of textural equilibrationor of diffusion-limited growth during quenching. Distinctioncan be made between these two processes by a consideration ofgrain shape. The geometry of interstitial phases in suites offully solidified cumulates from the Rum Layered Intrusion showsvariable approach to sub-solidus textural equilibrium from aninitial state inherited by pseudmorphing of the last melt. Texturalequilibration at pore corners occurs as a continuous process,with a gradual movement of the entire dihedral angle populationtowards the equilibrium final state. If the initial, pseudomorphedstate is one of disequilibrium (i.e. a melt-present impingementtexture) this change is accompanied by a reduction in the spreadof the population. If it is one of equilibrium, the change isaccompanied by an initial increase in the spread of the population,followed by a decrease. These observations demonstrate thatpreviously published models of dihedral angle change involvingthe instantaneous establishment of the equilibrium angle inthe immediate vicinity of the pore corner are incorrect. KEY WORDS: cumulate; dihedral angle; textural evolution; Rum intrusion; Kula; Santorini     

Entanglement of Australian sea lions and New Zealand fur seals in lost fishing gear and other marine debris before and after Government and industry attempts to reduce the problem

In recent years, Australian governments and fishing industry associations have developed guiding principles aimed at reducing the impact of fishing on non-target species and the benthos and increasing community awareness of their efforts. To determine whether they reduced seal entanglement in lost fishing gear and other marine debris, we analysed Australian sea lion and New Zealand fur seal entanglement data collected from Kangaroo Island, South Australia. Contrary to our expectations, we found that entanglement rates did not decrease in recent years. The Australian sea lion entanglement rate (1.3% in 2002) and the New Zealand fur seal entanglement rate (0.9% in 2002) are the third and fourth highest reported for any seal species. Australian sea lions were most frequently entangled in monofilament gillnet that most likely originated from the shark fishery, which operates in the region where sea lions forage--south and east of Kangaroo Island. In contrast, New Zealand fur seals were most commonly entangled in loops of packing tape and trawl net fragments suspected to be from regional rock lobster and trawl fisheries. Based on recent entanglement studies, we estimate that 1478 seals die from entanglement each year in Australia. We discuss remedies such as education programs and government incentives that may reduce entanglements.     

Non-linear stability around the triangular libration points

The configuration space around the triangular libration points in the Earth-Moon system is partitioned according to the stability of the motion. The regions aroundL ₄ andL ₅ are established where particles placed with zero initial velocity will librate. The complexity of the partitioning is revealed.