Large-eddy simulation of flows past a flapping airfoil using immersed boundary method

The numerical simulation of flows past flapping foils at moderate Reynolds numbers presents two challenges to computational fluid dynamics: turbulent flows and moving boundaries. The direct forcing immersed boundary (IB) method has been developed to simulate laminar flows. However, its performance in simulating turbulent flows and transitional flows with moving boundaries has not been fully evaluated. In the present work, we use the IB method to simulate fully developed turbulent channel flows and transitional flows past a stationary/plunging SD7003 airfoil. To suppress the non-physical force oscillations in the plunging case, we use the smoothed discrete delta function for interpolation in the IB method. The results of the present work demonstrate that the IB method can be used to simulate turbulent flows and transitional flows with moving boundaries

基于纳米间隔电极对的DNA分子结电输运的研究进展

脱氧核糖核酸分子是一类重要的生物分子,在生物医学领域之外,该类分子还因为其所具有的独特的双螺旋结构以及长程输运能力,在分子电子学领域也引起了研究者的极大兴趣.本文综述了近年来基于纳米间隔电极对构筑分子结这一研究范式,在构筑脱氧核糖核酸分子结以及研究后者的电输运性质等方面的研究进展.依据研究者所采用的不同纳米间隔电极对构筑技术,主要围绕裂结法和切割法两大类研究方法所展开.前者主要包括扫描隧道显微镜裂结法、导电原子力显微镜法、机械可控裂结法,后者则主要包括碳纳米管切割法、石墨烯切割法、硅纳米线切割法.在梳理不同实验方法的发展脉络、比较不同实验方法的各自特点的基础上,对一些具有代表性的关于脱氧核糖核酸分子结的研究工作进行了重点介绍,探讨了脱氧核糖核酸分子结所具有的与常规小分子体系所不同的特殊电学性质,同时对该领域的未来发展进行了展望.中南大学湘雅三医院“新湘雅人才工程”(No.20150203)国家重点研发计划(No.2017YFA0204902)国家自然科学基金(No.21722305)资助~

Genetic diversity and adaptive evolution of the major histocompatibility complex (MHC) class II DAB genes in the vulnerable Chinese egret (Egretta eulophotes)

主要组织相容性复合体（MajorHistocompatibilityComplex，MHC）对于脊椎动物识别、呈递外来抗原起着重要的作用。脊椎动物机体MHC免疫功能的正常执行有赖于MHC基因的高度多态性。MHC基因作为典型的适应性分子标记（Adaptivemarker），已被广泛应用于种群适应性进化等研究，并已成为进化生态学及保护遗传学领域的研究热点。黄嘴白鹭（Egrettaeulophotes）是国家II级重点保护动物、国际自然保护联盟（InternationalUnionforConservationofNature，IUCN）易危物种。本文深入研究黄嘴白鹭MHCII类DAB基因多态性及其...The major histocompatibility complex (MHC) consists of genes that play an important role in susceptibility and/or resistance to many vertebrate diseases, principally by recognizing foreign peptides and presenting them to T cells of the immune system, thus initiating the adaptive immune response. MHC genes are valuable genes for studies of evolutionary and conservation biology because of their dive...学位：理学博士院系专业：环境与生态学院_生态学学号：3332013015389

Martensitic transformation pathways and crystallographic orientation relationships in steel

Martensite is one of the most important structures determining the ability to tailor the performance of steel and several other engineering materials. In previous studies, the face-centered cubic (FCC) to hexag-onal close-packed (HCP) (or body-centered cubic (BCC)) martensitic transformation and the FCC to body-centered tetragonal (BCT) (or BCC) martensitic transformation during deformation and quenching were widely investigated; these transformations usually improve the plasticity and strength of steel, respec-tively. In this work, detailed transmission electron microscopy (TEM) observations and electron diffraction pattern analyses of the BCT and BCC twins are performed along the [110], [131], and [1 over bar 53] zone axes. The transformation of BCT twins into BCC twins along the [131] zone axis is also analyzed through in situ heating during the TEM observations. The high-resolution TEM observations of mutually perpendicular BCT variants are consistent with the atomic arrangement obtained for the quenching pathway during the martensitic transformation. In addition, different orientation relationships between austenite and marten-site are explained in terms of the atomic migration occurring during the deformation pathway and the quenching pathway of the martensitic transformation.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology

A study of intermodal transport coordination and its contribution to sustainable urban transportation in Hong Kong

published_or_final_versionTransport Policy and PlanningMasterMaster of Arts in Transport Policy and Plannin

Frequency-wavenumber energy spectra in isotropicturbulence

对均匀各向同性湍流的频率波数能量谱进行了初步研究，得出均匀各向同性湍流中能量随时间、空间尺度分布的解析表达式，并运用直接数值模拟的方法对理论预测进行验证．数值结果很好地支持了理论预测：横扫速度是决定频率波数能量谱的特征量

浸入边界/大涡模拟混合方法模拟翼型绕流的转捩问题

以雷诺数Re=60000静止翼型SD7003和扑动翼型SD7003绕流为例,验证结合浸入边界和大涡模拟的混合方法模拟流动转捩的能力。对于静止翼型绕流算例,结合浸入边界和大涡模拟的混合方法可以很好地预测转捩点以及再附点。对于扑动翼型绕流的算例,目前方法给

火箭炮大推力机电伺服作动器疲劳稳定性研究

火箭炮大推力机电伺服作动器是以高精度行星滚柱丝杠为核心部件的直线传动机构。为研究行星滚柱丝杠副疲劳稳定特性，开展了行星滚柱丝杠无故障与有故障疲劳对比试验；通过试验数据曲线，分析了行星滚柱丝杠副轮齿缺损和有无润滑脂两种工况对丝杠副负载、位移、转速、温升的影响。研究结果表明，在部分轮齿缺损或无润滑脂两种工况下，行星滚柱丝杠副依然可以保持较为稳定的负载、位移、转速、温升曲线；火箭炮大推力机电伺服作动器行星滚柱丝杠副在轮齿受损或少润滑脂情况下可免维护或少维护使用

Large-eddy simulation of flows past a flapping airfoil using immersed boundary method

The numerical simulation of flows past flapping foils at moderate Reynolds numbers presents two challenges to computational fluid dynamics: turbulent flows and moving boundaries. The direct forcing immersed boundary (IB) method has been devel- oped to simulate laminar flows. However, its performance in simulating turbulent flows and transitional flows with moving boundaries has not been fully evaluated. In the present work, we use the IB method to simulate fully developed turbulent channel flows and transitional flows past a stationary/plunging SD7003 airfoil. To suppress the non-physical force oscillations in the plunging case, we use the smoothed discrete delta function for interpolation in the IB method. The results of the present work demonstrate that the IB method can be used to simulate turbulent flows and transitional flows with moving boundaries