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P. J. Hall 《Experimental Astronomy》2004,17(1-3):5-16
The pace of the international Square Kilometre Array (SKA) project is accelerating, with major concept reviews recently completed and a number of technology demonstrators well underway. First-round submissions to host the telescope were lodged by six countries. The SKA timeline currently shows a site decision in 2006, and one or more technology concepts chosen in 2008. The telescope is expected to be operational, in various phases, in the period 2015–2020. This paper gives a status review of the project, and outlines engineering concept development and demonstration projects. 相似文献
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The mechanisms of soil structure interaction have drawn much attention in the past years in the installation and operation of jack-up platform. A bionic spudcan produced by biomimetic of egg and snail shell is proposed, and the performance of the penetration and extraction are analyzed by numerical method. The geometric contour of egg and snail shell is measured, and its mathematical model is established respectively. According to the structure of existing spudcan of jack-up platform, three kinds of typical biomimetic spudcan are designed. Furthermore, numerical analysis models of biomimetic spudcan are established respectively to study the soil structure interaction mechanism in the process of penetration and extraction, and contrastive analysis of resistance characteristics are carried out. To conclude, the results show that the biomimetic spudcan facilitates the platform installation, and it is also beneficial to the improvement of the bearing capacity of spudcan. 相似文献
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微细粒低品位锰矿由于颗粒间的非选择性聚集、浮选药剂用量大、浮选效率低等技术难题而致使其利用困难,造成大量浪费。在品位低于13%的锰矿浮选技术研究中,捕收剂最受关注,前人已研究了多种类型的捕收剂,所得精矿品位在16.9%~18.3%之间,回收率为56%~97%,回收率比较理想,但精矿品位总体不高。本文将新型捕收剂RA-92应用于湖南凤凰-花垣地区低品位碳酸锰矿(锰品位为10.7%)的选矿工艺中,实验研究了磨矿细度、pH值、抑制剂和捕收剂用量对浮选效果的影响,在最佳工艺条件下,精矿品位由原矿的10.7%提升至17.4%,回收率达到80.2%。研究表明RA-92对碳酸锰矿具有良好的捕收性能,浮选工艺相对简单且捕收剂用量少,浮选成本较低,可为此种捕获剂在微细粒低品位碳酸盐锰矿选矿中的应用得到推广。 相似文献
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对采自海南文昌红树林根际土壤样品中分离到的真菌Penicillium sp. MA-37的次生代谢产物的化学成分进行了研究.利用硅胶柱层析、葡聚糖凝胶Sephadex LH-20柱层析、制备薄层层析以及重结晶等分离方法并通过现代波谱技术共分离、鉴定了8个天然产物,分别为:氮-(2-甲氧基-4-羟基苯)-丙酰胺酸(1),氮-(2,4-二甲氧基苯)-丙酰胺酸(2),氮-(2,4-二甲氧基苯)-丙酰胺酸甲酯(3),(22E,24R)-麦角甾-5,7,22-三烯-3β-醇(4),(22E,24R)-麦角甾-4,6,8(14),22-四烯-3-酮(5),(22E,24R)-5α,8α-环二氧麦角甾-6,22-双烯-3β-醇(6), asperamide B (7), cis-4-hydroxy-6-deoxyscytalone (8);其中化合物1为新化合物,化合物2和3为新天然产物. 相似文献
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传统铷原子钟和铯原子钟已在卫星导航定位系统中作为星载原子钟获得重要应用.卫星导航定位系统的更新和新发展要求更高精度更小型的新型星载原子钟.该文介绍采用新物理原理和先进技术在下-代卫星导航定位系统有应用前景的新原子钟的产生和发展以及它们目前的进展. 相似文献
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Paul Robbins 《Geographical review》2019,109(2):252-257
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Geographers have been thinking and teaching about human interactions with the environment for centuries. Whether the phrase used to describe this area of scholarship is man‐land, man and nature, people‐environment, nature‐society, human dimensions of global change, or the Anthropocene, these studies are deeply rooted under the umbrella of geography. Scholars in the natural sciences, social sciences, humanities, and creative arts have embraced the concept of the Anthropocene, and often employ it as a vernacular term with no implied connection to a so‐called golden spike, or stratigraphic layer of sediment or rock that would mark an official transition from one slice of geologic time to the next. This collection of essays explores ways in which the Anthropocene may be a helpful framework to organize geographical teaching and scholarship about ways in which people have interacted with and transformed planet Earth. The term Anthropocene was coined in the realm of Earth System science, but the authors who contributed to this Forum relate the idea to topics such as novel ecosystems and species assemblages, conservation, commodification of nature, global capitalism, and ways in which our species, Homo sapiens, has markedly transformed the Earth for at least thousands of years. The Forum also engages with the fact that the Anthropocene as a proposed new epoch of the geologic time scale may not make sense at the spatial and temporal scales at which geographers view the world. Geographers have an opportunity to address myriad unanswered questions about the Anthropocene. 相似文献
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为考虑钻井船插桩对邻近平台群桩相互作用的影响，以海洋平台群桩设计中使用的修正Poulos法为基础，提出了一种考虑桩靴贯入影响的群桩分析方法。该法基于非线性地基梁模型确定桩靴贯入土层时单桩桩头位移；依据桩同时承受桩头荷载与土体位移时对应的地基反力系数确定土层的弹性模量，进而在Poulos群桩相互作用分析理论框架内，分析桩靴贯入对群桩相互作用的影响，确定桩靴贯入过程中由于群桩相互作用导致的附加桩头位移及相应的群桩桩头位移；依据群桩桩头位移，确定考虑桩靴贯入影响的群桩p-y曲线Y因子及相应的p-y关系。为了说明分析方法的可行性，进行了桩靴贯入砂土时对邻近单桩和群桩相互作用影响的离心模型试验，方法预测与试验结果基本一致，从而验证了方法的合理性。对于文中的工况，桩靴贯入没有导致群桩p-y关系进一步弱化，此时采用桩靴贯入前的群桩p-y关系确定考虑桩靴贯入影响的群桩响应，得到的结果偏安全。 相似文献
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海上自升式钻井平台以其造价低廉、便于移动和安装的优势被广泛应用于海洋地质勘察、风电安装和油气开采等领域,其基础类型多为桩靴基础。为了保证平台能在恶劣的海洋环境中安全作业,桩靴基础需要贯入海床以下一定深度以获得足够的承载力。然而,当桩靴基础在上硬下软土层中贯入时可能发生穿刺破坏导致平台损坏甚至倾覆。已有的桩靴穿刺破坏分析方法基于预设的地层参数预测穿刺荷载,由于无法考虑海床中地层及土性的不确定性,其准确性有待提高。将桩靴基础贯入过程中的监测数据与穿刺破坏机理相结合,通过66组离心机模型试验结果表征土体不确定性的影响,发展贝叶斯预测模型,实现了峰值阻力和穿刺深度的实时预测。基于规范推荐的荷载扩展分析法和冲剪系数分析法,建立了适用于规范法的概率模型,采用该模型对上砂下黏土层中桩靴基础的穿刺行为进行了预测,结果表明所提方法的预测精度随着监测数据的增加而提高,预测得到的峰值阻力误差在10%以内。 相似文献