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基于相场描述的拉压不对称强度结构拓扑优化 被引量:4
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作者 张晓鹏 康柯 杨东生 《计算力学学报》 EI CAS CSCD 北大核心 2020年第6期670-676,共7页
运用了基于相场描述的拓扑优化方法,来寻找在拉伸和压缩中表现出不对称强度行为的连续体结构的最优布局。依据Drucker-Prager屈服准则和幂率插值方案,优化问题可以描述为在局部应力约束下的最小化结构的体积。用qp放松法来解决应力约束... 运用了基于相场描述的拓扑优化方法,来寻找在拉伸和压缩中表现出不对称强度行为的连续体结构的最优布局。依据Drucker-Prager屈服准则和幂率插值方案,优化问题可以描述为在局部应力约束下的最小化结构的体积。用qp放松法来解决应力约束的奇异性,并采用基于P-norm函数的聚合方法对应力约束进行凝聚,该方法实现了约束个数的降低,同时引入了稳定转化法来处理大量的局部应力约束和高度非线性的应力行为,以修正应力,提高优化收敛的稳定性。在优化问题求解时,使用拉格朗日乘子法对目标函数和应力约束进行处理。利用伴随变量法进行灵敏度分析,并通过求解Allen-Cahn方程更新相场函数设计变量。数值算例证明了该优化模型和相应数值技术的有效性,相关算例还揭示了考虑拉压不同强度和考虑同拉压强度约束时得到的结构优化拓扑构型具有显著的差异。 展开更多
关键词 结构拓扑优化 应力约束 相场函数 拉压不对称强度
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融合车尾边缘特征的前车识别与纵向车距检测 被引量:4
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作者 程文冬 袁伟 +1 位作者 张名芳 李震 《机械设计与制造》 北大核心 2017年第7期152-156,共5页
以提升车辆主动安全、减少纵向碰撞事故为目标,提出了一种基于车尾边缘特征信息的前车识别方法与基于单目视觉的纵向车距检测方法。有别于传统算法利用全局边缘特征或灰度纹理特征来识别前车,该算法首先依据路面灰度分布特性来分割车底... 以提升车辆主动安全、减少纵向碰撞事故为目标,提出了一种基于车尾边缘特征信息的前车识别方法与基于单目视觉的纵向车距检测方法。有别于传统算法利用全局边缘特征或灰度纹理特征来识别前车,该算法首先依据路面灰度分布特性来分割车底阴影,再利用车尾水平与竖直边缘的分布特性建立前车ROI,进一步利用竖直边缘的对称强度验证车辆身份。根据摄像机的小孔成像原理建立纵向车距测量模型,避免了复杂的内外部参数标定。道路试验表明,算法对车辆的平均识别率达到88.5%,纵向车距检测的平均相对误差小于3%,能够实现的有效测距范围为(6.9~78.3)m,其精度与运行速度可以满足实际驾驶中的纵向车距检测。 展开更多
关键词 高级驾驶辅助系统 梯度边缘方向直方图 对称强度 纵向车距模型
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混凝土板的轴对称冲切强度 被引量:10
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作者 王安宝 杨秀敏 +1 位作者 史维纷 王年桥 《建筑科学》 2000年第5期17-19,35,共4页
采用双剪应力三参数强度准则和刚塑性模型 ,对混凝土板轴对称冲切强度进行了分析 ,给出了轴对称破坏机构 ,得到极限应力圆的包络线为二条直线 ,利用虚功原理求得破坏荷载的上限。公式形式简洁 ,与已有结果相比符合较好。
关键词 双剪强度理论 混凝土板 对称冲切强度
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Study on High-Temperature Spectra of Asymptotic Asymmetric-Top Molecule O_3 被引量:1
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作者 SONG Xiao-Shu GUO Yun-Dong +3 位作者 LING-HU Rong-Feng Lv Bing CHENG Xin-Lu YANG Xiang-Dong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2008年第8期481-485,共5页
The line intensities of 001-000 transition of the asymptotic asymmetric-top Oa molecule at several temperatures are calculated by directly calculating the partition functions and regarding the rotationless transition ... The line intensities of 001-000 transition of the asymptotic asymmetric-top Oa molecule at several temperatures are calculated by directly calculating the partition functions and regarding the rotationless transition dipole moment squared as a constant. The calculated values of the total internM partition sums (TIPS) are consistent with the data of HITRAN database with -0.61% at 296 K. The calculated line intensity data at 500 K and 3000 K are also in excellent agreement with the data in HITRAN database with less than 0.659% and 5.458% at 500 K and 3000 K, which provide a strong support for the calculations of partition function and fine intensity at high temperature. Then we extend the calculation to higher temperatures. The line intensities and simulated spectra of v3 band of the asymptotic asymmetric-top O3 molecule at 4000 and 5000 K are reported. The results are of significance for the studying of the molecular high-temperature spectrum including experimental measurements and theoretical calculations. 展开更多
关键词 asymptotic asymmetric-top molecule line intensities partition functions high temperature spectrum
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Extension of Direct Displacement-Based Design to Plan-Asymmetric RC Frame Buildings
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作者 Alessandro Paparo Luca Landi Pier Paolo Diotallevi 《Journal of Civil Engineering and Architecture》 2012年第10期1280-1291,共12页
The object of this paper is the evaluation of the seismic response of reinforced concrete frames designed according to the DDBD (direct displacement-based design) approach. The great part of research works about DDB... The object of this paper is the evaluation of the seismic response of reinforced concrete frames designed according to the DDBD (direct displacement-based design) approach. The great part of research works about DDBD has been dedicated to planar frames, but recently also some proposals for 3D structures have been presented, in particular for wall structures. This paper will give a further contribution to the extension of the procedure for the case of plan-asymmetric RC (reinforced concrete) frames. The extended methodology is aimed at accounting for the floor rotations on the basis of a given lateral strength distribution along the plan. The procedure was applied to two plan-asymmetric RC frames, characterized by the same geometry but different lateral strength distributions along the plan. The seismic behavior of the designed frames was studied by adopting a fiber model and by performing pushover and nonlinear dynamic analyses. 展开更多
关键词 Direct-displacement-based design pushover analysis non-linear dynamic analysis plan-asymmetric structures
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同位旋相关量探测重离子碰撞趋平衡及对称能 被引量:1
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作者 李庆峰 李祝霞 《高能物理与核物理》 EI CSCD 北大核心 2002年第9期926-932,共7页
用IQMD模型分析了由96 Ru和96 Zr构成的质量对称、同位旋不对称的一组中能核反应 ,寻求对对称势强度的敏感量和研究反应最终是否达到平衡的问题 .研究表明中子 -质子差快度分布在弹或靶快度区对对称势强度敏感 ,且越丰中子的核系统越敏... 用IQMD模型分析了由96 Ru和96 Zr构成的质量对称、同位旋不对称的一组中能核反应 ,寻求对对称势强度的敏感量和研究反应最终是否达到平衡的问题 .研究表明中子 -质子差快度分布在弹或靶快度区对对称势强度敏感 ,且越丰中子的核系统越敏感 .中子 -质子差快度分布还表明能量为 40 0MeV/u时达到的平衡程度要比 1 0 0MeV/u时的高 .出射的核子、轻带电粒子和中等质量碎片的N/Z显示IMF的出射有记忆效应 .随着入射能量由 1 0 0MeV/u增加到 40 0MeV/u ,IMF的N/Z有明显下降 ,这是由于随入射能量增加使IMF中同位素的分布发生变化所致 . 展开更多
关键词 探测 重离子碰撞 对称 同位旋 对称强度 反应平衡性
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环境规制与公平竞争:理论逻辑、现实解析及协调思路——基于异质性企业的视角 被引量:1
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作者 田露露 韩超 姜春海 《上海财经大学学报(哲学社会科学版)》 CSSCI 北大核心 2024年第2期50-64,共15页
在公平竞争理念已成为全社会基本共识的情形下,其与环境规制的关系少有涉及和探讨。为此,文章首先厘清了环境规制与公平竞争之间关系的理论逻辑,接着基于异质性企业视角,从规制立法并未考虑企业的异质性、规制执法的选择性和偏向性、作... 在公平竞争理念已成为全社会基本共识的情形下,其与环境规制的关系少有涉及和探讨。为此,文章首先厘清了环境规制与公平竞争之间关系的理论逻辑,接着基于异质性企业视角,从规制立法并未考虑企业的异质性、规制执法的选择性和偏向性、作为市场主体不正当竞争的工具、促使企业向规制强度较弱地区转移四方面归纳了环境规制影响公平竞争的具体路径。随后从现实原因与理论症结层面解析二者相冲突的深层次原因,发现规制方式不完善、地方执法机构专业性与独立性缺乏、规制理论并未包含公平竞争是造成此现象的根源所在。最后提出须通过在环境规制中引入公平竞争、基于企业的异质性完善既有规制方式、提高环境规制机构的专业性与独立性、协调区域间环境规制政策四个途径对二者的关系加以改进。文章为在环境规制领域践行公平竞争理念提供了理论参考和现实路径。 展开更多
关键词 环境规制 公平竞争 异质性企业 规制方式 对称规制强度
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A Four-Element Sensor Array Consisting of Asymmetric Distributed-Feedback Fiber Lasers 被引量:2
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作者 Pengpeng WANG Jun CHANG +7 位作者 Cunguang ZHU Boning SUN Guangping LV Sasa ZHANG Yanjie ZHAO Zhihui SUN Xiaolei ZHANG Gangding PENG 《Photonic Sensors》 SCIE EI CAS 2014年第2期180-187,共8页
A sensor array system formed by arranging four asymmetric distributed-feedback fiber lasers (DFB-FL) in ascending order according to their slope efficiencies was proposed. The output flatness could be effectively im... A sensor array system formed by arranging four asymmetric distributed-feedback fiber lasers (DFB-FL) in ascending order according to their slope efficiencies was proposed. The output flatness could be effectively improved with the application of asymmetric DFB-FLs. The last element had almost the same output with the others although it obtained the smallest pump power. The relative intensity noise (RIN) and relaxation oscillation frequency of the sensor array were also analyzed. It is found that the relaxation oscillation frequency of a certain DFB-FL was relevant to its relative position in the array. And the RIN of a certain DFB-FL was always affected by the other elements in the array, which was not dependent on the order of their arrangement. 展开更多
关键词 Asymmetric DFB fiber laser sensor array intensity noise relaxation oscillation
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Numerical simulations on origin of Galilean moons' magnetic anomalies 被引量:1
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作者 JIAO LiGuo KUANG WeiJia MA ShiZhuang 《Science China Earth Sciences》 SCIE EI CAS 2011年第11期1754-1760,共7页
Galileo mission detected the magnetic anomalies originated from Galilean moons.These anomalies are likely generated in the moons' interiors,under the influence of a strong ambient Jovian field.Among various possib... Galileo mission detected the magnetic anomalies originated from Galilean moons.These anomalies are likely generated in the moons' interiors,under the influence of a strong ambient Jovian field.Among various possible generation mechanisms of the anomalies,we focus on magneto-convection and dynamos in the interiors via numerical simulation.To mimic the electromagnetic environment of the moons,we introduce in our numerical model an external uniform magnetic field B0 with a fixed orientation but varying field strength.Our results show that a finite B0 can substantially alter the dynamo processes inside the core.When the ambient field strength B0 increases to approximately 40% of the field generated by the pure dynamo action,the convective state in the core changes significantly:the convective flow decreases by 80% in magnitude,but the differential rotation becomes stronger in much of the fluid layer,leading to a stronger field generated in the core.The field morphologies inside the core tend to align with the ambient field,while the flow patterns show the symmetry-breaking effect under the influence of B0.Furthermore,the generated field tends to be temporally more stable. 展开更多
关键词 Galilean moons magnetic fields magneto-convection DYNAMO
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Effect of solvent on directional drift in Brownian motion of particle/molecule with broken symmetry
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作者 FanDong Kong Nan Sheng +2 位作者 RongZheng Wan GuoHui Hu HaiPing Fang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2016年第8期28-33,共6页
The directional drifting of particles/molecules with broken symmetry has received increasing attention. Through molecular dynamics simulations, we investigate the effects of various solvents on the time-dependent dire... The directional drifting of particles/molecules with broken symmetry has received increasing attention. Through molecular dynamics simulations, we investigate the effects of various solvents on the time-dependent directional drifting of a particle with broken symmetry. Our simulations show that the distance of directional drift of the asymmetrical particle is reduced while the ratio of the drift to the mean displacement of the particle is enhanced with increasing mass, size, and interaction strength of the solvent atoms in a short time range. Among the parameters considered, solvent atom size is a particularly influential factor for enhancing the directional drift of asymmetrical particles, while the effects of the interaction strength and the mass of the solvent atoms are relatively weaker. These findings are of great importance to the understanding and control of the Brownian motion of particles in various physical, chemical, and biological processes within finite time spans. 展开更多
关键词 directional drift asymmetrical particle solvent
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