Modelling nonlinear time-dependent pipeline walking induced by SCR tension and downslope     

《Applied Ocean Research》2019

Subsea pipelines are important facilities in offshore oil and gas industry to transport High-Pressure and High-Temperature (HPHT) hydrocarbon. They are often exerted by cyclic thermal loading through the whole operational life, which may trigger asymmetry in the effective axial force (EAF) profile, leading to a global axial movement, defined as ‘pipeline walking’. It may cause the downtime and structural risks, since this directional accumulation in axial movement results in the overstressing of end connection, loss of tension in a steel catenary riser (SCR) and other issues in the field, therefore subsea pipeline design requires a reliable estimate of the global pipeline walking rate. Current design methods adopt a constant soil friction coefficient and ignore variations in soil-pipeline interaction with time during the heating up and cooling down processes. In reality, the overlooked changing soil friction is important, and may alter the pipeline walking behaviours. To achieve an accurate assessment of pipeline walking, this paper advances the conventional design practice, by introducing a time-dependent axial soil friction function, to examine the pipeline walking behaviour over the operational thermal cycles. A suite of time-dependent matrixes is provided to reveal the development of the expansion/contraction of the pipeline, the corresponding mobilised soil frictions and the EAF profile. The significant nonlinear EAF profile in response to the time-dependent soil friction is examined, and is used to well assess the accumulation in pipeline walking rate. The proposed analytical framework is applied into case studies to demonstrate its validity and applicability in practice.  相似文献   

Controls on geomorphic characteristics of the Xiaohei River basin in the upper Lancang-Mekong,China     

GU Zhen-kui  FAN Hui  LOU Jun-peng  YANG Kun 《山地科学学报》2020,17(5):1032-1044

Understanding the evolution of the fluvial geomorphology in an orogenic belt provides valuable insight into the relationship between upper crustal deformation and surface processes.The upper Lancang-Mekong River is in an area experiencing both uplift and erosion.The related processes provide a steady sediment supply to the lower reaches of the river and play an important role in the regional environmental changes.The Xiaohei(Weiyuan)River Basin is an important sub-basin in this area,which is characterized by large-scale topographic fluctuations,active tectonics and erosion,and anthropogenic activities.These different factors introduce numerous complexities to the local surface processes.In this study,we investigate and quantify the controls of geomorphic evolution of the Xiaohei River Basin.We located and mapped the main knick-zones within the channels and examined the main genetic factors,such as faults and stratigraphic differences.The results show that the areas with the lowest uplift rates are characterized by a low steepness index and are located in the southeastern part of the basin.The stream power of the mainstream increases downstream,with an average value of^122 W/m.The erosional activity of the various stream channels is intense.Overall,the basin tends to expansion,with only local instances of inward contraction.Our analysis confirms that a number of the geomorphic evolutionary characteristics of the Xiaohei River Basin are transient.In addition,the future potential for the increasing the number of dams and the hydropower development in the basin may weaken the expansion trend of the basin over a long period of time.  相似文献   

印度暴力袭击事件的时空演变及其驱动机制     

曾卓  熊理然  蒋梅英 《热带地理》2019,39(6):869-879

基于全球恐怖主义数据库（GTD）和南亚恐怖主义门户网站（SATP）所收录的印度暴力袭击事件数据,借助统计分析和核密度分析法,对1980—2017年印度暴力袭击事件时空演变及其驱动机制进行分析。结果表明：印度国内的暴力袭击事件频发,1980年以来呈现出波动上升态势。从空间上看,印度国内的暴力袭击事件具有自西到东、从北到南以及由边境地区向内地发展的扩散特点,展现出局部集中、面上扩散的发展趋势;呈现出以西北部的查馍-克什米尔地区和旁遮普邦、东北部的阿萨姆邦和曼尼普尔邦、中部的恰蒂斯格尔邦和东部的贾坎德邦、比哈尔邦和西孟加拉邦为主的四大集聚中心;形成以印度河上游—恒河—布拉马普特拉河一线为横轴,东高止山脉及其北部山区为纵轴的“T”字形空间格局。印度暴力袭击事件的时空演变受到身份认同、经济问题、历史问题和利益诉求等多方面因素的影响,通过宗教极端主义组织、民族分离主义组织、武装革命主义组织推动以及行动主体之间的互相作用,推动了暴力袭击事件的时空演变。要从根本上解决印度国内暴力袭击事件频发的态势,需要从政治、经济、宗教、社会等多方面进行综合施策。  相似文献   

可视化水下航行体控制系统数学仿真软件设计     

黄凡 《数字海洋与水下攻防》2020,3(4):355-362

提供一种水下航行体控制系统数学仿真软件的设计方案，在该仿真软件平台上可以完成水下航行体控制系统数学仿真研究、水下航行体水动力参数辨识实验和实航内测数据及仿真实验结果三维可视化显示。详细设计了该软件包含的 4 大模块：水下航行体数学模型及仿真模型模块、控制算法模块、流体动力参数辨识模块和图形界面人机交互模块，并对仿真模型的配置做了简单介绍。  相似文献   

Evaluation System for Yunnan Cultural Tourism Routes Based on a Five Component Model: Case Study of the Ancient Tea-horse Road in the South of Yunnan     

WANG Yan  XIE Hongzhong  ZHU Tao 《资源与生态学报(英文版)》2019,10(5):553-558

Cultural tourism routes can reveal and protect cultural tourism heritage by means of cultural tourism in the “time category” and the “space category”. The construction of an evaluation system for cultural tourism routes and the evaluation, scoring and grading of existing and potential cultural tourism routes are the key to the protection of heritage, history and culture along these routes, and the key to encouraging the standardization, branding and sustainable development of various formats on the routes. Yunnan cultural tourism routes are diverse and rich in resources, and their developmental foundation is good. However, the tourism development and cultural development activities occur along separate lines and there is a lack of unified management. Therefore, it is necessary to conduct research on information collection, information analysis, problem diagnosis and improvement of status in the local practices of Yunnan cultural tourism routes, and to guide the sustainable development of Yunnan cultural tourism routes. Based on the advanced experience of COE (Council of Europe), UNESCO WHC (United Nations Educational, Scientific and Cultural Organization, World Heritage Committee) and ICOMOS(International Council on Monuments and Sites), this paper comprehensively analyzes the decisive criteria for line evaluation by interpreting and summarizing the connotations of cultural tourism routes, and determines that the evaluation of cultural tourism routes should include lines. Five aspects―the theme, the participating subject, the object itself, related activities and multi-party value―are used to construct a five-component model. At the same time, based on the consumer utility function, a complete route evaluation and hierarchical system is constructed. Then, taking the Ancient Tea-horse Road cultural tourism route as an example and using the expert scoring method and the analytic hierarchy process, the actual scores and grades of the Ancient Tea-horse Road cultural tourism route are determined, and countermeasures and suggestions for its sustainable development are proposed. The paper also verifies the applicability and practicability of the evaluation system, and promotes and improves the feedback evaluation system. The aim is to at promote and widely apply the evaluation system of cultural tourism routes, realizing the transformation from individual cases to joint cases, and promoting the standardization and sustainable development of cultural tourism routes.  相似文献   

Isotopic analysis of the super-large Shuangjianzishan Pb–Zn–Ag deposit in Inner Mongolia,China: Constraints on magmatism,metallogenesis, and tectonic setting     

《Ore Geology Reviews》2016

The super-large Shuangjianzishan Pb–Zn–Ag deposit is a newly discovered deposit located in the Huanggang–Ganzhuermiao polymetallic metallogenic belt of Inner Mongolia, NE China. The deposit's resource includes 0.026 Mt Ag, 1.1 Mt Pb, and 3.3 Mt Zn. The deposit is controlled by a NW-trending ductile shear zone and NE- and NW-trending faults in black pelite assigned to the lower Permian Dashizhai Formation. LREE enrichment, HREE depletion, Nb, Ta, P, and Ti depletion, and Zr and Hf enrichment characterize felsic magmatic rocks in the Shuangjianzishan Pb–Zn–Ag district. The ages of porphyritic monzogranite, rhyolitic crystal–vitric ignimbrite, and porphyritic granodiorite are 254–252, 169, and 130 Ma, respectively. Pyrite sampled from the mineralization has Re–Os isochron ages of 165 ± 7 Ma, which suggest the mineralization is associated with the ca. 169 Ma magmatism in the Shuangjianzishan district.Zircons extracted from the porphyritic granodiorite yield ε_Hf(t) values of − 11.34 to − 1.41, with t_DM2 dates of 1275–1901 Ma. The ε_Hf(t) values of zircons in the rhyolitic crystal–vitric ignimbrite and the ore-bearing monzogranite porphyry are 7.57–16.23 and 10.18–15.96, respectively, and their t_DM2 ages are 177–733 and 257–632 Ma, respectively. Partial melting of depleted mantle resulted in the formation of the ca. 254–252 Ma ore-bearing porphyritic monzogranite and the ca. 169 Ma rhyolitic crystal–vitric ignimbrite; dehydration partial melting of subducted oceanic crust resulted in the formation of the ca. 130 Ma porphyritic granodiorite. The porphyritic monzogranite was emplaced during the late stages of closure of the Paleo-Asian Ocean during the transformation from a collisional to extensional tectonic setting. The ca. 170 and ca. 130 Ma magmatism and mineralization in the Shuangjianzishan district are related to subduction of the Mongolia–Okhotsk Ocean and subduction of the Paleo-Pacific Ocean Plate, respectively.  相似文献   

Late Cretaceous magmatism and related metallogeny in the Tengchong area: Evidence from geochronological,isotopic and geochemical data from the Xiaolonghe Sn deposit,western Yunnan,China     

《Ore Geology Reviews》2016

Xiaolonghe is a poorly studied greisen-type tin deposit that is hosted by biotite granite in the western Yunnan tin belt. The mineralisation-related metaluminous and weak peraluminous granite is characterised by high Si, Al and K and low Mg, Fe and Ca, with an average A/CNK of 1.02. The granite is enriched in LILEs (K and Rb), LREEs and HFSEs (Zr, Hf, Th, U and Ce) and depleted in Ba, Nb, Sr, P, and Ti, with zircon εHf(t) = − 10.8 to − 7.5 (T_DM2 = 1.61–1.82 Ga). These characteristics indicate that the magma was generated by the partial melting of a thickened ancient crust. LA-ICP-MS U–Pb dating of igneous zircon and hydrothermal cassiterite yield ages of 71.4 ± 0.4 Ma and 71.6 ± 4.8 Ma, respectively. The igneous biotite and hydrothermal muscovite samples show Ar–Ar plateau ages of 72.3 ± 0.4 Ma and 70.6 ± 0.2 Ma, respectively. The close temporal relationship between the igneous emplacement and hydrothermal activity suggests that the tin mineralisation was closely linked to the igneous emplacement. The δ¹⁸O and δD values for the deposit range from + 3.11‰ to − 4.5‰ and from − 127.3‰ to − 94.7‰, respectively. The hydrothermal calcite C and O isotopic data show a wide range of δ¹³C_PDB values from − 5.7‰ to − 4.4‰, and the δ¹⁸O_SMOW values range from + 1.4‰ to + 11.2‰. The δ³⁴S_V-CDT data range from + 4.8‰ to + 8.9‰ for pyrite, and the ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.708 to 18.760, from 15.728 to 15.754 and from 39.237 to 39.341, respectively. The stable isotopic (C–H–O–S–Pb) compositions are all similar to those of magmatic and mantle-derived fluids, which indicate that the ore-forming fluids and materials were mainly derived from magmatic sources that were accompanied by meteoric water. The tin mineralisation in the Xiaolonghe district was closely associated with the Late Cretaceous crustal-melting S-type granites that formed during the subduction of the Neo-Tethys oceanic lithosphere. Combined with the tin deposits in the Southeast Asian tin belt, Tengchong block and Central Lhasa, we interpreted that a giant intermittent tin mineralisation belt should be present along the Asian Neo-Tethys margin.  相似文献   

Mineralogy and mineral chemistry of Bi-minerals: Constraints on ore genesis of the Beiya giant porphyry-skarn gold deposit,southwestern China     

《Ore Geology Reviews》2016

The Beiya deposit, located in the Sanjiang Tethyan tectonic domain (SW China), is the third largest Au deposit in China (323 t Au @ 2.47 g/t). As a porphyry-skarn deposit, Beiya is related to Cenozoic (Himalayan) alkaline porphyries. Abundant Bi-minerals have been recognized from both the porphyry- and skarn- ores, comprising bismuthinite, Bi–Cu sulfosalts (emplectite, wittichenite), Bi–Pb sulfosalts (galenobismutite, cosalite), Bi–Ag sulfosalt (matildite), Bi–Cu–Pb sulfosalts (bismuthinite derivatives), Bi–Pb–Ag sulfosalts (lillianite homologs, galena-matildite series), and Bi chalcogenides (tsumoite, the unnamed Bi₂Te, the unnamed Ag₄Bi₃Te₃, tetradymite, and the unnamed (Bi, Pb)₃(Te, S)₄). Native bismuth and maldonite are also found in the skarn ores. The arsenopyrite geothermometer reveals that the porphyry Au mineralization took place at temperatures in the range of 350–450 °C and at log fS₂ in the range of − 8.0 to − 5.5, respectively. In contrast, the Beiya Bi-mineral assemblages indicate that the skarn ore-forming fluids had minimum temperatures of 230–175 °C (prevailing temperatures exceeding 271 °C) and fluctuating fS₂–fTe₂ conditions. We also model a prolonged skarn Au mineralization history at Beiya, including at least two episodes of Bi melts scavenging Au. We thus suggest that this process was among the most effective Au-enrichment mechanisms at Beiya.  相似文献   

海河流域夏季降水与北半球环流异常的相关     

马宁  谢均  郭军  何群 《气象科技》2016,44(3):400-407

使用1981—2013年6—8月的月平均海河流域站点降水资料以及NCEP/NCAR再分析资料,采用SVD方法分析了北半球高度场环流异常与海河流域夏季降水的关系。结果表明夏季海河流域的一致型降水异常主要受热带地区高度场异常的影响,而北半球中高纬的高度异常分布对海河流域东南部降水异常有重要作用。热带及中高纬地区的高度场异常与副热带西风急流和流域上空的水汽输送有一定的对应关系,急流强度和位置的变化以及水汽辐合异常造成海河流域降水异常,尤其中高纬高度异常的这种对应关系更加明显,并且两个地区的高度异常分布对应的海河流域异常水汽输送有不同来源。  相似文献   

利用地形正规化校正反立体现象     

章皖秋  岳彩荣  袁华 《遥感学报》2016,20(4):590-600

影像目视判读常会遇到山脊与沟谷的凹凸感与现实相反的反立体现象。消除反立体现象,能有效提高非专业人员对遥感影像的正确使用。立足于反立体现象的成因,本文采用地形正规化模型来校正影像的反立体现象,推导出Lambertian、Cosine-Civco、c校正、b校正这4种地形正规化模型的反立体校正式;对这4种地形正规化模型的反立体校正效果进行了对比,并且与其他5种校正法也进行了对比。通过3个实验区的校正发现,这4种地形正规化模型均能校正反立体现象,但校正影像存在色调偏差;Lambertian、Cosine-Civco的反立体校正影像立体感较强,但影像色调改变较大,视觉效果偏差;c校正、b校正的校正影像在视觉效果和定量指标上都比较接近,基本保持地物光谱信息,校正效果相对较好。从定量指标来看,b校正的反立体校正影像的各指标值整体最小,一定程度代表b校正能取得相对较好的反立体校正效果。与其他方法的对比表明,c校正和b校正的反立体校正不局限于波段个数,在有效消除反立体现象的同时,能相对较好的保留地物光谱信息,有利于影像的定量应用。  相似文献