基于SIMP方法微电容加速度计结构固有频率拓扑优化

基于连续体结构拓扑优化的SIMP材料插值模型,以叉指式微电容加速度计弹性梁和质量块的一阶固有频率最大化为目标函数,以体积比作为约束条件,建立了弹性梁和质量块的拓扑优化模型。采用优化准则算法进行迭代求解计算。获得了满足不同体积约束并使一阶固有频率最大的微电容加速度计弹性梁和质量块的多种拓扑优化结构,其中28%体积比约束下的拓扑优化结构与其初始结构相比,一阶固有频率提高了3 330 Hz,提高比例达46.4%。计算结果表明通过构建的拓扑优化模型及优化求解方法可以较好地解决微加速度计频响范围过窄的问题。     

纯电动汽车正面抗撞结构耐撞性拓扑优化方法

为了解决纯电动汽车正面碰撞安全性差的问题,文章提出了一种综合考虑5种典型碰撞工况下整车优化区域以及动力电池布置分析的多目标耐撞性拓扑优化方法。基于混合元胞自动机(hybrid cellular automata,HCA)算法,耐撞性拓扑优化以单元相对密度为设计变量、结构内能密度分布统一为目标,运用固体各向同性微结构材料惩罚模型(solid isotropic material with penalization model,SIMP)下的变密度法进行材料分布;迭代收敛后,最终得到了传力路径优越、构型明朗清晰的耐撞性车身结构,同时得到符合整车性能要求的吸能纵梁形状。对优化后的整车模型进行的耐撞性验证表明,该优化结构让碰撞加速度与结构变形量同步最优化,大大增加了纯电动汽车正面碰撞的安全性,优化出的抗撞结构为纯电动汽车正面耐撞性设计提供了一定的参考。     

热力耦合问题的拓扑优化算法

研究材料在热力耦合作用下的拓扑优化结构。基于固体各向同性惩罚法,建立材料热力耦合问题拓扑优化算法。基于Freefem++软件编写热力耦合问题的拓扑优化程序,并使用该程序计算了二维悬臂梁在热力耦合作用下的拓扑优化结构。     

基于Ordered SIMP插值模型的 点阵-实体复合结构拓扑优化设计方法

为了提高点阵材料结构件的力学性能,提出了一种基于Ordered SIMP方法的点阵-实体复合结构拓扑优化方法.采用一种三维X型微结构单元作为点阵材料,通过数值拟合建立点阵材料相对密度与其等效物理属性之间的函数关系.在宏观结构拓扑优化问题中,以点阵材料等效密度为设计变量,基于Ordered SIMP插值方法建立点阵材料和实体材料相结合的多材料插值模型,进而,以材料体积用量为约束,以结构柔度最小化为目标实现点阵-实体复合结构的多尺度拓扑优化设计.通过数值算例和实验测试表明,相比于仅使用点阵材料填充的设计,本方法能够获得更好的结构刚度.     

渗流问题的拓扑优化

分析拓扑优化中的密度惩罚函数插值法SIMP（Solid isotropic material with penalization model）,将结构力学中的拓扑优化方法应用到渗流问题的拓扑优化设计中,用有限元的方法建立了简单的理想状态下的渗流问题的拓扑优化数学模型,并采用基于剃度法的数值解法-优化准则法（OC系列算法）,以设计具有最小能量损耗情况下的流体最佳流动路径的拓扑分布。以一组二维渗流问题为例,说明了该模型的有效性,为渗流问题的优化设计提供了一种有效的新思路和方法。     

基于RAMP模型的ICM连续体拓扑优化方法

基于RAMP插值函数和独立连续映射(ICM)法,提出了一个新的拓扑优化模型. 模型采用不同参数RAMP插值函数对单元体积和单元刚度阵进行过滤识别. 与SIMP插值函数下的ICM拓扑优化模型相比,仅一、二阶导数表达式不同,拓展了优化建模方法并保证了优化求解算法的一致性. 通过拓扑优化数值算例对不同模型参数下的拓扑优化结果进行了对比分析. 结果表明,该方法适用于连续体拓扑优化建模.     

基于类桁架材料模型优化方法计算稳定性研究

推导了2相正交类桁架材料模型,建立了基于类桁架连续体材料模型的单工况和多工况应力约束拓扑优化方法.以杆件在结点位置的密度和方向为设计变量,在单工况下,采用满应力准则法优化杆件密度,将杆件方向与主应力方向对齐;在多工况下,采用方向刚度包络线拟合的方法,由各单工况优化结构导出.通过反复迭代形成类桁架连续体材料优化分布场,进而形成类桁架结构.通过3个经典算例,验证了不同有限单元网格密度和形状下该拓扑优化方法的稳定性,克服了各种拓扑优化普遍存在的单元依赖性.     

基于并行策略的热固耦合多材料柔顺机构设计

热效应在结构设计领域受到广泛的重视,文中利用拓扑优化的方法,对热驱动柔顺机构设计进行了研究,提出了相应的基于并行策略的求解模型.该模型的核心是将一个复杂的多材料热固耦合问题离散成为单材料热固耦合子问题,然后对这些子问题并行求解,并根据整体目标的需要,对所有子问题的解进行调整以得到原始问题的解.对所有的单材料子问题,基于SIMP(固体各向同性材料惩罚模型)材料插值模型,建立了热固耦合拓扑优化求解模型,然后利用顺序耦合方法进行热-结构多物理场耦合分析,独立并行求解.该模型在理论和实践上都比较简单,可以处理任意多种材料,并且可以避免零碎的拓扑结构,因而有利于制造.文中还通过数值算例说明了此方法的有效性.     

精细拓扑结构表示与深度特征融合在多目标图像检索中的应用

空间信息表示是增强图像特征表达性能的重要手段,通过空间关系建模与深度学习方法融合可有效提升深度特征的语义特性,从而提升图像检索性能.首先,针对复杂图像的空间关系表示提出了一种新的精细拓扑结构表示模型,该模型不仅具有完备的拓扑描述性能,还提供了两种拓扑不变量的推理算法,使得拓扑不变量可以由表示模型直接推导而不需要繁复的几何计算;其次,基于精细拓扑结构表示模型,提出了有效的拓扑结构相似性度量方法,为空间关系特征表达奠定了基础;最后,进一步结合卷积神经网络,提出融合复杂空间关系特征与深度特征的多目标图像检索方法.实验结果表明,所提出的拓扑结构表示模型在空间查询中具有良好的性能;所提出的图像检索框架取得优于现有方法的精度,并能够有效地结合手工特征与深度特征各自的优势,为提升深度学习方法的可解释性创造了有利条件.     

SIMP拓扑优化的拉压杆模型研究

采用SIMP应变能最小化的优化准则方法,对基于拓扑优化技术建立拉压杆模型的设计流程进行了深入研究.并对基于SIMP法拓扑优化建立拉压杆模型的影响因素进行了系统研究,总结出将最优拓扑转化为构件拉压杆模型的原则.为验证其最优性,对一简支开洞深梁建立了多种拉压杆模型,并与基于SIMP法的拓扑优化建立的拉压杆模型,通过承载能力和有效系数进行方案的比选.研究结果表明基于SIMP拓扑优化的拉压杆模型应变能和钢筋体积比最小,而承载能力较大.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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