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991.
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993.
传统的基于全站仪等单点测量技术难以获取钢结构整体信息,且测量速度慢、模型重建精度低。针对此问题,本文将三维激光扫描技术应用于钢结构模型重建领域,提出了基于LiDAR点云的复杂钢结构模型重建方法。首先,基于标靶球和钢结构面信息实现多测站点云的高精度配准,并通过半径滤波算法去除噪点,以得到完整的激光点云数据;然后,对复杂钢结构单体模型进行分割,以实现各个部件的模型重建;最后,根据现场实测数据对重建的三维模型进行精度评估。试验结果表明,基于该方法得到的模型精度较高,与实际尺寸差值均小于1 cm,为复杂钢结构的三维模型重建提供了有效解决方案。 相似文献
994.
COVID-19疫情不断蔓延为国际政治、外交关系等带来深刻影响。目前基于复杂网络方法的国际关系研究较少考虑节点的空间属性,难以探索国际关系的动态演化模式及其空间分布特征。该文提出一种结合时间序列聚类与空间统计的国家关系交互网络演化模式探测方法。基于2020年1月-2021年3月的GDELT数据构建国家关系交互网络,基于节点的演化特征,应用K-means聚类算法将节点划分为6种类型,结合局部连接统计方法分析节点演化模式的空间分布特征。研究表明:面对疫情冲击,各国为控制疫情蔓延倾向于参与合作交互事件;国家关系交互网络中的不同时序演化模式总体按照节点的点度中心性强度由高到低分布;疫情防控期间网络中始终处于边缘地位的节点在空间分布上呈现聚集特征,而核心节点空间分布较分散。通过研究网络节点的时序演化模式及空间分布特征可为公共卫生危机事件期间国际关系与地缘政治研究提供新思路,对于危机事件期间制定外交政策与应对策略具有一定参考价值。 相似文献
995.
U–Pb dating of detrital zircons was performed on mélange-hosted lithic and basaltic sandstones from the Inthanon Zone in northern Thailand to determine the timing of accretion and arc activity associated with Paleo-Tethys subduction. The detrital zircons have peak ages at 3400–3200, 2600–2400, 1000–700, 600–400, and 300–250 Ma, similar to the peaks ages of detrital zircons associated with other circum-Paleo-Tethys subduction zones. We identified two types of sandstone in the study area based on the youngest detrital zircon ages: Type 1 sandstones have Late Carboniferous youngest zircon U–Pb ages of 308 ± 14 and 300 ± 16 Ma, older than associated radiolarian chert blocks within the same outcrop. In contrast, Type 2 sandstones have youngest zircon U–Pb ages of 238 ± 10 and 236 ± 15 Ma, suggesting a Middle Triassic maximum depositional age. The youngest detrital zircons in Type 1 sandstones were derived from a Late Carboniferous–Early Permian ‘missing’ arc, suggesting that the Sukhothai Arc was active during sedimentation. The data presented within this study provide information on the development of the Sukhothai Arc, and further suggest that subduction of the Paleo-Tethyan oceanic plate beneath the Indochina Block had already commenced by the Late Carboniferous. Significant Middle Triassic arc magmatism, following the Late Carboniferous–Early Permian arc activity, is inferred from the presence of conspicuous detrital zircon U–Pb age peaks in Type 2 sandstones and the igneous rock record of the Sukhothai Arc. In contrast, only minimal arc activity occurred during the Middle Permian–earliest Triassic. Type 1 sandstones were deposited between the Late Permian and the earliest Triassic, after the deposition of associated Middle–Late Permian cherts that occur in the same mélanges and during a hiatus in Sukhothai Arc magmatism. In contrast, Type 2 sandstones were deposited during the Middle Triassic, coincident with the timing of maximum magmatism in the Sukhothai Arc, as evidenced by the presence of abundant Middle Triassic detrital zircons. These two types of sandstone were probably derived from discrete accretionary units in an original accretionary prism that was located along the western margin of the Sukhothai Arc. 相似文献
996.
997.
湖北省的磷矿资源储量居全国之首,矿床类型以元古宙海相沉积型磷块岩矿床为主,分布集中在五大区域,开发利用条件较好。虽然湖北的磷矿资源勘查近年取得了突破性的进展,但由于资源利用合理度欠缺、磷化工企业规模小、产业链不完善及产业集中度低等原因,对磷矿开发和磷化工产业的可持续发展构成了制约。磷矿资源的合理开发利用对建设磷矿开发及磷化工产业集群、保障国家粮食安全具有重要意义。因此,在勘查部署上,要根据成矿条件、空间富集规律和勘查开发现状,统一部署,分类开展工作;在产业布局上,以宜昌、保康、荆襄、黄麦岭4大磷化工基地为主体,新建鹤峰、黄梅磷肥基地,打造"一圈多点"式产业集群;在产业关联上,新建磷矿产地与现有磷化工基地之间形成以老带新、以新助老、空间互动的产业格局;在产品分工上,支持现有磷化工基地内的骨干企业兼并重组,提高产业集中度。 相似文献
998.
汶川地震断裂带科学钻探三号孔(WFSD-3)事故处理与认识 总被引:1,自引:0,他引:1
WFSD-3孔因地层破碎、缩径,不可预知因素多,发生多起孔内事故,通过对钻铤脱扣、下套管卡钻、埋钻等不同事故原因分析、事故处理,对WFSD-3孔施工工艺做出了改进与调整,总结了对科学钻探孔事故预防与处理的经验体会。 相似文献
999.
The Koraput Alkaline Complex in the high-grade Eastern Ghats Belt, India, is synkinematically emplaced in a pull-apart structure and far from the Bastar cratonic margin. The suite comprises four distinct members, namely, mafic syenite, felsic syenite, nepheline syenite and perthite syenite. Fe-rich orthopyroxene rims on olivine in mafic syenite indicate iron-enrichment in the early stage of differentiation. With plagioclase of andesine composition it could be described as alkali-norite, the plutonic equivalent of hawiite. Felsic syenite with both alkali-feldspars and plagioclase of oligoclase composition could be described as two-feldspar syenite, the plutonic equivalent of mugearite. Albitic rims on nepheline indicates subsolvus reaction. Chemical trends in amphiboles and plagioclase feldspars, progressively more ferroan and more sodic respectively, are strong indications of mineral fractionation in the Koraput suite. Chemical trends in the variation diagrams are compatible with feldspar fractionation in the Koraput suite. A weak Fe-enrichment trend in the early stage of differentiation, as observed in the AFM diagram, is compatible with that of the alkali-basalt series. Nb anomalies, both positive and negative, are indicative of crustal contamination as expected in synkinematic plutons. In terms of Gondwana assembly and break up, the alkaline complexes are supposed to represent rift-related magmatism along the continental margin. In spite of petrological evidence of the magmatic character of the Koraput Complex, anorogenic setting is contra-indicated by mesoscopic and microscopic fabrics, more akin to synkinematic intrusion during F 2 folding in the host country rocks. The Proterozoic alkaline complexes in the Eastern Ghats Belt, could alternatively trace the path of moving Gondwana continent over mantle plumes. 相似文献
1000.