Extracting energy while reducing hydroelastic responses of VLFS using a modular raft wec-type attachment     

《Applied Ocean Research》2019

This paper presents the use of a modular raft Wave Energy Converter (WEC)-type attachment at the fore edge of a rectangular Very Large Floating Structure (VLFS) for extracting wave energy while reducing hydroelastic responses of the VLFS under wave action. The proposed modular attachment comprises multiple independent auxiliary pontoons (i.e. modules) that are connected to the fore edge of the VLFS with hinges and linear Power Take-Off (PTO) systems. For the hydroelastic analysis, the auxiliary pontoons and the VLFS are modelled by using the Mindlin plate theory while the linear wave theory is used for modelling the fluid motion. The analysis is performed in the frequency domain using the hybrid Finite Element-Boundary Element (FE-BE) method. Parametric studies are carried out to investigate the effects of pontoon length, PTO damping coefficient, gap between auxiliary pontoons, and incident wave angle on the power capture factor as well as reductions in the hydroelastic responses of the VLFS with the modular attachment. It is found that in oblique waves, the modular attachment comprising multiple narrow pontoons outperforms the corresponding rigid attachment that consists of a single wide pontoon with respect to the power capture factor and the reduction in the deflection of the VLFS. In addition, it is possible to have a considerable gap between pontoons without significantly compromising the effectiveness of the modular attachment.  相似文献   

皋兰老虎台红砂种群在不同坡向的空间格局及关联性          下载免费PDF全文

刘旻霞  南笑宁  夏素娟  李全弟  蒋晓轩 《干旱区地理》2019,42(6):1359-1367

种群的空间格局是研究植物种群相互作用及种群与环境关系的重要方法。红砂（Reaumuria soongarica）是黄土高原半干旱区的主要物种，通过野外的群落调查，运用空间点格局分析法中的Ripley K函数，分析甘肃皋兰老虎台荒漠植被不同坡向红砂种群的空间分布格局与种内关联。结果显示：红砂种群为增长型种群，其在不同坡向的分布具有显著差异；南坡及西南坡坡向上，红砂种群Ⅰ、Ⅱ级个体在小尺度上呈显著聚集分布，随着龄级及空间尺度的增加，红砂种群聚集强度逐渐减弱，最后趋于随机分布。西坡、西北坡坡向上生长大量的蓍状亚菊（Ajania achilloides）和短花针茅（Stipa breviflora）等对红砂的生长造成抑制并加剧种间竞争，各级红砂种群的分布格局均以随机分布为主。不同坡向上，红砂种群Ⅰ、Ⅱ龄级个体之间在小尺度内表现为负关联，随着尺度增加关联度降低，Ⅲ、Ⅳ龄级与Ⅰ、Ⅱ龄级个体之间呈显著的负关联，而Ⅲ、Ⅳ龄级之间没有明显关联性，表明龄级相近的个体在空间分布上是相互独立的。综上所述，在黄土高原半干旱区，影响红砂种群分布的主要因素除了其自身的生物、生态学特性外，微生境的影响也十分重要。  相似文献   

地基干涉雷达IBIS-S桥跨结构振动变形测量与模态分析   总被引：2，自引：0，他引：2  

王鹏  邢诚  项霞 《测绘通报》2019,(10):35-39

地基雷达干涉测量技术能够以较高的时空采样频率获取线性结构目标整体瞬时变形状态。本文将该技术引入大型桥梁桥跨结构的振动变形测量与模态分析中。对动静载试验过程中的武汉二七长江大桥东岸桥跨结构开展连续变形监测，利用频域分解法计算桥跨结构的自振频率、阻尼比和模态振型。计算结果表明，地基干涉雷达干涉测量技术能够快速探测桥跨结构竖弯模态，特别适用于灾后大型线形结构健康状态的应急检测。  相似文献   

Terrestrial heat flow and lithospheric thermal structure in the Chagan Depression of the Yingen-Ejinaqi Basin,north central China     

Yinhui Zuo  Shu Jiang  Shihu Wu  Wei Xu  Jiong Zhang  Renpeng Feng  Meihua Yang  Yongshui Zhou  M. Santosh 《Basin Research》2020,32(6):1328-1346

The Chagan Depression in the Yingen-Ejinaqi Basin, located at the intersection of the Paleo-Asian Ocean and the Tethys Ocean domains is an important region to gain insights on terrestrial heat flow, lithospheric thermal structure and deep geodynamic processes. Here, we compute terrestrial heat flow values in the Chagan Depression using a large set of system steady-state temperature data from four representative wells and rock thermal conductivity. We also estimate the “thermal” lithospheric thickness, mantle heat flow, ratio of mantle heat flow to surface heat flow and Moho temperature to evaluate the regional tectonic framework and deep dynamics. The results show that the heat flow in the Chagan Depression ranges from 66.5 to 69.8 mW/m², with an average value of 68.3 ± 1.2 mW/m². The Chagan Depression is characterized by a thin “thermal” lithosphere, high mantle heat flow, and high Moho temperature, corresponding to the lithospheric thermal structure of “cold mantle and hot crust” type. We correlate the formation of the Yingen-Ejinaqi Basin to the Early Cretaceous and Cenozoic subduction of the western Pacific Plate and the Cenozoic multiple extrusions. Our results provide new insights into the thermal structure and dynamics of the lithospheric evolution in central China.  相似文献   

New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone,Arabian Sea     

《China Geology》2020,3(2):269-282

Seabed fluid escape is active in the Makran subduction zone, Arabian Sea. Based on the new high-resolution 2D seismic data, acoustic blanking zones and seafloor mounds are identified. Acoustic blanking zones include three kinds of geometries: Bell-shaped, vertically columnar and tilted zones. The bell-shaped blanking zone is characterized by weak and discontinuous reflections in the interior and up-bending reflections on the top, interpreted as gas chimneys. Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity, which may together serve as a vent structure. Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope. Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion. Bottom simulating refectors (BSRs) are widely distributed and exhibit a series of characteristics including diminished amplitude, low continuity as well as local shoaling overlapping with these acoustic blanking zones. The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments, followed by the formation of the gas hydrates and hence the seafloor mound.  相似文献   

基于遗传算法优化BP神经网络的玉米遥感估产方法     

于海洋  陈圣波  杨北萍  安秦 《世界地质》2020,39(1):208-214

以内蒙古自治区开鲁县玉米作物为研究对象,将生育期内玉米遥感影像所提取的多种植被指数和实地采样点的测产数据作为训练值,利用BP(back propagation)神经网络和遗传算法优化BP(GA-BP)神经网络估产模型,得出网络预测的玉米产量数值。通过决定系数R 2和均方根误差RMSE,比较实测产量与预测产量之间的精度,BP神经网络模型R^2为0.8452,RMSE(%)为28.37;遗传算法优化BP神经网络模型R^2为0.9850,RMSE(%)为6.70,表明遗传算法优化BP神经网络估产模型具有一定可行性和可信度。  相似文献   

Winkler model for dynamic response of composite caisson–piles foundations: Seismic response     

《Soil Dynamics and Earthquake Engineering》2014

A simplified method with a dynamic Winkler model to study the seismic response of composite caisson–piles foundations (CCPF¹) is developed. Firstly, with the dynamic Winkler model, the kinematic response of the CCPF subjected to vertically propagating seismic S-wave is analyzed by coupling the responses of caisson part and pile part. Secondly, a simplified model for the foundation–structure system is created with the structure simplified as a lumped mass connected to the foundation with an elastic column, and through the Fast Fourier Transformation (FFT) this model is enabled to solve transient seismic problems. Thirdly, the proposed method for the seismic response of CCPF-structure systems is verified by comparison against 3D dynamic finite element simulation, in which the Domain Reduction Method (DRM²) is utilized. Lastly, the mechanism and significance of adding piles in improving the earthquake resistance of the foundation and structure is analyzed through an example with different soil conditions. Discovered in this study is that adding piles under the caisson is an efficient way to increase seismic resistant capability of the soil–foundation–structure system, and the main mechanism of that is the elimination of the pseudo-resonance.  相似文献   

东营凹陷沙河街组碳酸盐胶结物成因机制     

孟伟  隋风贵  郝雪峰  张守鹏  秦峰  伍松柏 《地质论评》2021,67(Z1):67z1107-67z1108

正碳酸盐矿物是砂岩储层中主要的成岩产物之一。碳酸盐胶结物较为活跃,其溶蚀及沉淀广泛发育于砂岩储层内。碳酸盐的溶蚀及沉淀是砂岩储层改造的重要成因之一。明确碳酸盐胶结物的成因机制对预测深部储层具有重要的意义。本次研究,采用铸体薄片及扫描电镜观察,明确碳酸盐胶结物的产状。对不同产状碳酸盐胶结物的分布、  相似文献   

太行山中段城南庄一带隐伏岩体及找矿前景分析     

吴云霞 《地质与勘探》2021,57(2):315-324

麻棚和赤瓦屋岩体都位于太行山中段热液金属矿成矿区内,在其周围已发现石湖石英脉大型金矿等60余处热液型矿床(点),其深部和外围可能存在找矿前景。本文通过探讨太行山中段城南庄一带遥感环形构造和重力负场特征与金属矿床和岩体的耦合关系,从城南庄卫星式-多层蘑菇群式遥感环形构造群、重力负场、中酸性岩脉侵入和温泉五种证据,推测城南庄深部存在比麻棚和赤瓦屋岩体大近六倍、面积约700 km~2的中酸性隐伏岩体—城南庄隐伏岩体。城南庄隐伏岩体边界基本与布格重力负异常边界吻合,呈长轴北东向宽缓带状展布,向南西方向倾伏,北侧埋深较浅、南侧埋深较深。城南庄隐伏岩体边部(特别是产状缓外倾,具有良好成矿空间的区域)和顶部与围岩的接触带位置、环形构造形成的晚期"小岩体"内部及附近位置和中酸性岩脉附近位置是寻找热液型矿床的有利部位。  相似文献   

鄂尔多斯盆地延安地区山西组山2段储层可动流体赋存影响因素分析     

刘江斌 《地质与勘探》2021,57(1):231-240

山2段是鄂尔多斯盆地延安地区致密砂岩气生产的重要层段,目前对其流体赋存规律认识明显不足。因此在铸体薄片、扫描电镜、X射线衍射、高压压汞、恒速压汞、核磁共振测试的基础上,分析该储层可动流体的赋存特征及其影响因素。结果表明:山2储层主要为岩屑石英砂岩和岩屑砂岩,溶蚀孔和晶间孔为主要储集空间,粒间溶孔显著发育。山2储层可动流体饱和度为34.74%～91.83%,平均为69.94%,T2谱多为双峰态,呈左低右高型。储层孔隙度、渗透率、孔隙类型、孔喉特征及胶结物影响可动流体饱和度。孔隙为可动流体提供主要空间,平均孔隙半径越大,平均喉道半径越大,孔喉比越小,可动流体饱和度越高。硅质含量越高,粒间孔保存越好,可动流体饱和度越高。铁方解石含量越高,孔隙破坏越明显,可动流体饱和越低。高岭石含量较高,长石溶孔及晶间孔发育较好,有利于流体流动,可动流体饱和度也较高。  相似文献