Effect of wing planform on leading-edge vortex structures

Flow visualization experiments are conducted in water tunnel for low aspect ratio cropped wings at low Reynolds number. The experimental results show that the model sweep angle Λ influences the formation and development of the leading-edge vortex. For wings with Λ =0°, the dominant flow structure is transverse vortex. When Λ≥26°, the dual vortex structure can be observed at some angles of attack, and it is confirmed that the dual vortex is a special structure for flow over low aspect ratio wing at low Reyno...     

Experimental investigation on the flow structure over a simplified Papilio Ulysses model

The aerodynamic characteristics of butterflies, especially those which can migrate overseas, have received a great deal of attention because they have larger-scale wingspans and lower flapping frequencies than other insects such as drosophilae and bees. The objective of this work is to investi-gate the flow structures over a simplified model of Papilio Ulysses, one kind of migratory butterflies, through hydrogen bubble visualizations, and leading-edge vortices, wing-tip vortices, separation bub-bles and horseshoe vortex wake are observed. Moreover, the variations of these structures with the angle of attack are discussed in detail. A new type of leading-edge vortices which resembles the in- versed Chinese character “八” is observed in the experiment.     

基于FrFT滤波和LMS降噪的变转速滚动轴承故障诊断

变速工况下的机械故障诊断逐渐成为旋转机械监控领域的一个热门课题,在变转速下故障更容易发生且伴随更大的噪声,而相应的降噪问题目前却没有可靠的解决方法。因此提出一种基于分数阶傅里叶变换（FrFT）滤波和最小均方算法（LMS）降噪的故障诊断方法,对变转速工况下轴承振动信号进行降噪,进而提取非平稳故障特征。首先,同时获得滚动轴承振动加速度信号和转速信号;然后对Hilbert解调后的振动信号进行峰值搜索FrFT,按照搜索得到的最佳阶次和分数阶域聚集位置进行FrFT滤波;再将FrFT滤波得到的信号作为参考信号,原包络信号作为输入信号,进行LMS自适应降噪;最后对降噪后的信号按照转速重采样进行阶次分析,将包络阶次谱中的突出特征与故障特征阶次对比,判断故障。该方法可成功应用于变转速工况下滚动轴承的试验数据处理,证明了方法的有效性。     

Characteristics of Early Eocene radiolarian assemblases of the Sasa area, southern Tibet and their constraint on the closure history of the Tethys

Quantitative analysis of Early Eocene radiolarian assemblages discovered in the sedimentary melange （accretionary prism） of the Saga area, southern Tibet provides new information to constrain the timing of Tethys closure and the initial collision of India and Eurasia. The radiolarian species of Saga include Amphisphaera coronata （Ehrenberg）, Buryella hannae Bak ＆ Barwicz-Piskorz, Buryella clinata Foreman, Buryella tetradica Foreman, Calocycloma ampulla （Ehrenberg）, Lamptonium fabaeforme constrictum Riedel and Sanfilippo, Lamptonium pennatum Foreman, Lithomespilus coronatus Squinabol and Lamptonium （？） colymbus Foreman. The adequate and reliable correlation of these radiolarians specimens indicates that the assemblage is of Early Eocene in age. The age and depositional environment of these radiolarians testify that deep ocean basins existed between India Plate and Asia Plate during the Early Eocene. The complete closure of Tethys must have taken place at least after the Early Eocene.     

光敏色素B介导光信号影响水稻的脱落酸途径

研究表明,拟南芥中光敏色素介导的光信号与植物激素脱落酸(abscisic acid,ABA)途径相互作用.但水稻光敏色素与ABA途径之间是否相互影响仍不清楚.利用野生型和phyB突变体水稻作为研究材料,分析phyB介导的光信号对ABA生物代谢和ABA反应的影响.结果表明,ABA合成代谢相关基因OsNCED1,OsNCED2,OsNCED3和OsNCED4在phyB突变体中的表达水平明显高于野生型,而ABA降解代谢基因OsABAOX1则相反,这可能解释了phyB突变体积累较多内源ABA的原因.外源ABA处理明显抑制黑暗和光照下生长的水稻种子的萌发,但光照条件下ABA对phyB突变体种子萌发的抑制效果更明显.据此推测,phyB感受的光信号消弱了ABA对种子萌发的抑制效果.通过分析部分已报道的种子萌发相关基因在正常或ABA处理的野生型和phyB突变体中的表达水平,结果表明,phyB介导的光信号对水稻种子萌发的调控作用可能与这些基因无关.此外,在红光条件下,ABA处理能够抑制水稻幼苗地上部分的生长,野生型和phyB突变体对ABA处理的反应基本相同;但是ABA对phyB突变体主根生长的抑制效果显著高于野生型,这个结果表明phyB介导的光信号不影响ABA对水稻幼苗地上部分生长的抑制效果,但负调控ABA对主根生长的抑制效果.上述研究结果表明,phyB介导的光信号负调控水稻ABA的积累和ABA反应.本研究揭示了水稻光敏色素对ABA途径的影响,为深入研究光信号途径和ABA途径之间协同调控水稻发育的分子机制奠定了基础.     

基于粘弹性分析的含蜡原油触变性研究

触变性是含蜡原油的一个重要流变性质，输油管道运行的安全性分析需要对触变行为做出准确的定量描述。从粘弹性力学角度出发，在弹性应力和粘性应力两方面分析含蜡原油在触变过程中的力学响应，做出若干合理的假设，推出新的触变性计算模型。该模型物理意义明确，可用于求取停输管道的再启动压力。对大庆原油和中原加剂原油进行了触变实验，用该模型对实验数据进行了非线性最小二乘法回归，结果表明，该模型能够较准确地预测触变行为。与其他触变模型相比，该模型具有参数较少和精度较高等特点。     

Multi-dimensional overall regulatory modes and threshold values for water cycle of the Haihe River Basin

In this study, a multi-dimensional critical regulatory criteria and decision-making mechanism based on the scientific cognition of multi-dimensional attributes and characteristics of the water cycle was proposed. This system was functioned by deeply discriminating the nature-society binary characteristics of the five-dimensional characteristics of the water cycle system of the Haihe River Basin (water resources, economy, society, ecology, and environment) under the influence of high-intensity human activities and hydrological changes and by analyzing the organic interactive relationships between the five dimensions and their overall effect on the water cycle. A GDP calculation model was constructed in this study by adjusting the water environment for water resources, after which five-dimensional normalization objective functions were established for multi-objective analysis to carry out trade-off analysis of multi-dimensional regulatory indexes. In addition, synergetic theory, entropy theory and dissipation structure theory were introduced to construct an evaluation model for multi-dimensional regulatory schemes. A water cycle multi-dimensional critical overall regulatory model system was also established. This system consisted of a multi-objective macroeconomic model (DAMOS), water resource allocation model based on rules (ROWAS), evaluation model for WEDP (EMW) and multi-dimensional regulatory scheme evaluation model (SEAMUR) as the main body. To address the national demands faced by the Haihe River Basin as a result of combinatorial schemes for different hydrological series and water amounts diverted by the south-to-north water diversion project, this study adopted a hierarchy progression method to set up the technologies, investigated multi-dimensional overall regulatory methods, proposed an overall regulation threshold value for the water cycle of the Haihe River Basin, and recommended corresponding five-dimensional regulatory schemes.     

Synthesis and photo-activity of peptide nucleic acids containing an azobenzene unit

We prepared the azobenzene PNA unit and synthesized various PNAs containing an azobenzene unit by a typical tBoc method. Both the azobenzene PNA unit and PNA containing an azobenzene unit （N-PNA） showed reversible photoisomerization with UV and visible light irradiation. The hybridization of N-PNA with complementary DNA resulted in a considerable decrease of the photoisomerization rate constant of the azobenzene.