Results 91 to 100 of about 16,458 (194)
Kongjian kexue xuebao圆形限制性三体问题共线平动点附近的平动点轨道由于其独特的动力学特性, 在深空探测任务中有着重要价值, 这些轨道间的轨道转移问题值得进行系统性研究. 针对平动点轨道的计算与延拓, 提出了一种基于数值的系统性计算平动点轨道的方法以及状态伴随法的轨道稳定维持策略. 在此基础上, 通过对大量平动点轨道不变流形以及平动点相空间中心流形的研究, 设计了一套通过脉冲机动实现平动点轨道间轨道转移的系统性解决方案. 该方法充分利用平动点动力学特性, 在仿真验证中证实了方案的有效性, 为平动点轨道转移研究提供了新的思路.
杨 富涛, 张 汉清
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Establishment of hydrodynamic model and research on motion simulation of open-frame ROV [PDF]
ObjectiveManeuverability is one of the most important performance characteristics of a Remotely Operated Vehicle (ROV), and is closely related to its dynamics model. To realize the precise control and maneuverability of an open-frame ROV, a dynamic model
Chaohe CHEN +3 more
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Conservation Biology, EarlyView.Abstract The design of experiments to investigate the combined effects of multiple stressors requires exposing target organisms to multiple combinations of stressor doses. Concurrent manipulation of stressors is often infeasible with wildlife, but long‐lasting health effects allow individual health to be used as an integrator of prior stressor exposure.
Enrico Pirotta +24 more
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Numerical Study on the Environment of Shenhu and Quanzhou Bays [PDF]
, 2007 本文以福建中部的两个半封闭的海湾——深沪湾和泉州湾为研究对象，通过数值模拟的方法再现了当地的潮汐潮流，浅滩干湿变化，污染物的输运，百年一遇的台风过境引起的增水现象和台风生成的波浪特征，在此基础上进一步探讨了不同动力机制对当地泥沙动力特性的影响。 结果发现：福建沿岸的潮汐潮流以规则半日潮为主，由于潮差较大，一些浅滩、湿地和暗礁在低潮时会露出水面，在高潮时又重新被海水淹没，形成周期性的干湿变化过程。模拟结果还显示：当天文分潮由外海传入海湾时 ...
刘浩
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Conservation Biology, EarlyView.Abstract Achieving global conservation policy goals requires the ability to set and measure progress toward science‐based targets for biodiversity. The species threat abatement and restoration (STAR) metric was developed to enable actors to set science‐based targets for species.
Louise Mair +17 more
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Harnessing social media data to track species range shifts
Conservation Biology, EarlyView.Abstract Biodiversity monitoring programs and citizen science data remain heavily biased toward the Global North. Especially in megadiverse countries with limited biodiversity records, incorporating social media data can help address existing data gaps.
Shawan Chowdhury +15 more
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, 1989 本文叙述了在定常流中,用平板模拟海底平面边界,在雷诺数R_e为4.0×10~3～1.5×10~5范围内,测量了孤立圆柱和离平板不同距离上的单柱的阻力(C_D)、升力(C_L)、上抬力(C_(LO))等水动力系数和响应频率f。研究了管道距平板边界的相对间距H/D(H为圆柱与平板之间的间距;D为圆柱直径 ...
凌国灿, 李战华, 鄂学全
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International Journal of Applied Linguistics, EarlyView.ABSTRACT Online tutoring platforms (OTPs) are an increasingly popular way for learners to study languages and for teachers to earn money. On many OTPs, individual teachers are responsible for attracting potential students via self‐branding. While scholarship has examined OTP teachers’ self‐branding practices and identified some of the most popular self‐
Wenjing Zeng, Nate Ming Curran
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Gaoya dianqi, 2016 文中基于某轨道交通直流断路器的总体结构模型,设计了一种快速电磁操动机构,对其结构和工作原理进行了阐述。基于电磁场分析理论,利用有限元分析软件ANSYS对电磁机构的静态特性进行了仿真分析,得出了在合闸状态下磁场分布和动铁心所受电磁吸力情况,并对其影响因素进行了分析。然后对电磁操动机构在不同电流条件下的电磁吸力随气隙变化进行了仿真分析,得出了机构空载条件下的动态输出插值数据。最后建立直流断路器动力学分析模型,借助动力学分析软件ADAMS,将建立的动态离散数据导入其中,对直流断路器动态分合特性进行了仿真 ...
王海燕 +5 more
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Jianzhu Gangjiegou Jinzhan, 2020 针对一个实际钢塔斜拉桥工程,采用有限元软件SAP2000进行了动力特性和地震反应分析,并以主塔为混凝土塔的苏通大桥作为参照,对斜拉桥的动力特性、主塔地震反应和抗震性能等进行了比较分析。结果表明:相对于混凝土塔,钢桥塔的刚度和质量较小,轴压比略大,斜拉桥纵飘和主塔侧弯振型周期较长,主塔重力几何刚度对桥梁动力特性的影响较大,从而显著增大了塔顶及主梁的纵向地震位移,但对主塔及其基础的地震内力影响较小。钢塔斜拉桥的抗震性能较好,在7度地震区,地震作用不会控制钢塔及其基础的结构设计。
朱家豪, 叶爱君, 韩大章, 华新
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