DOPA-PSPMA仿生共聚物综合探究性实验研究

为提高本科学生的创新创业能力,通过高分子化学实验教学使学生深入了解仿生共聚物的制备及性能的相关知识,设计了综合探究性实验。通过原子转移自由基聚合法制备仿生共聚物,并将其修饰在多种材料表面。采用X射线光电子能谱、扫描电子显微镜、生物显微镜分别对修饰材料进行表征。该实验通过共聚物的制备使学生掌握高分子化学中活性可控自由基聚合制备共聚物的方法;掌握仿生共聚物设计及构筑方法;使学生学习科研仪器的操作方法,切实提高学生的实践能力。该实验重复性好、创新性及拓展性强,将共聚物设计制备及应用有机结合,适用于高分子专业本科生综合探究性实验。     

Oscillation of shallow flow past a cavity: Resonant coupling with a gravity wave

Self-excited oscillations of flow past a cavity are generated in a shallow free-surface system. The shear layer past the cavity opening has two basic forms: a separated free-shear flow; and a shear flow along a slotted plate. Instabilities of these classes of shear flows can couple with the fundamental gravity-wave mode of the adjacent cavity. The dimensionless frequencies of both types of oscillations scale on the length of the cavity opening, rather than the gap distance between the slats, i.e., a large-scale instability is always prevalent. A technique of high-image-density particle image velocimetry allows acquisition and interpretation of global, instantaneous images of the flow pattern, including patterns of vorticity and Reynolds stress correlation. Use of a cinema approach provides representations of the timewise evolution of the global, instantaneous flow structure, and thereby definition of the amplitude peaks and phase angles of the coupled fluctuations via auto- and cross-spectral techniques. These methods, along with global, averaged representations of the fluctuating flow field, provide insight into the onset of fully coupled (phase-locked) oscillations of the shear flow past the resonator cavity. The common, as well as the distinctive, features of the resonant-coupled instability of the shear flow past the slotted plate are characterized, relative to the corresponding coupled instability of the free-shear layer. Varying degrees of resonant coupling between the unstable shear layer and the adjacent resonator are attained by variations of the inflow velocity, which yield changes of the predominant oscillation frequency, relative to the resonant frequency of the adjacent cavity. Well-defined, coherent oscillations are indeed attainable for the case of the shear flow along the slotted plate, though their amplitude is significantly mitigated relative to the case of a free-shear layer. The degree of organization of the self-excited, resonant-coupled oscillation and the manner in which it varies with open area ratio and geometry of the plate are interpreted in terms of the flow structure on either side of, and within, the slotted plate; these features are compared with the corresponding structure of the free-shear layer oscillations.     

Dual-phase-lag thermoelastic damping models for micro/nanobeam resonators

Thermoelastic damping (TED) affects the quality factors of vacuum-operated micro/nanobeam resonators significantly. In this work, by adopting the non-Fourier theory of dual-phase-lag (DPL) model, an analytical formula of TED in micro/nanobeam resonators with circular cross-section is first developed. Moreover, for micro/nanobeam resonators with rectangular cross-section, the series-form type of DPL-TED model is also proposed and compared with the modified existing model. The characteristics of TED spectra with the single-peak, dual-peak, and multiple-peak phenomena are explored. The simulation results reveal that the ratio of dual-phase-lag times and the characteristic dimension of beams such as the radius and thickness have significant influences on TED behaviors. In addition, temperature distributions in micro/nanobeams exhibit an apparent distinction under the DPL non-Fourier effect.     

Flow Mechanism and Simulation Approaches for Shale Gas Reservoirs: A Review

Transport in Porous Media - The past two decades have borne remarkable progress in our understanding of flow mechanisms and numerical simulation approaches of shale gas reservoir, with much larger...     

Improved accuracy phase retrieval in spatial phase-shifting interferometry

Algorithms for phase retrieval in spatial phase-shifting interferometry are examined. It is noticed that the classical Carré technique based on four neighbor pixels may introduce shaped phase residuals that affect the accuracy of the reconstruction. A variant of the technique is proposed, taking into consideration five pixels and steering the phase retrieval algorithm to the appropriate subset so that residuals are free of underlying errors. Computational results are presented illustrating the approach and demonstrating the accuracy improvement in a case study.     

A parallel three-dimensional scour model to predict flow and scour below a submarine pipeline

A three-dimensional Lattice Boltzmann flow and scour model is developed to simulate time-dependent scour below a submarine pipeline. The proposed model presented in this paper is able to predict streamwise and spanwise propagations of scour with respect to lattice unit of time. It is evident from this study that the existence of a spiral vortex in the proximity of the span shoulder is quite noteworthy. It is revealed that the critical regime of the 2-D scour process is found to be up to one pipe diameter away in both directions from the middle of the unsupported length of pipelines. The equilibrium maximum scour depth and the shape of streamwise equilibrium scour hole compare well with the available experimental data. The speed of propagation of scour along the pipeline length maintains an almost constant rate, which is consistent with the experimental observations found in literature. In addition, it is seen that the scour slope at the shoulder region remains fairly constant throughout the whole scour process.     

Remark on the variational principle in the AdS/CFT correspondence for the scalar field

We discuss how the variational principle can be used as a criterion for choosing, among scalar field actions implying the same equation of motion, the appropriate one for the AdS/CFT correspondence.     

介质阻挡放电低温等离子体脱硝性能研究

进行了介质阻挡放电低温等离子体脱除伴有SO₂的烟气中NO的研究,分别进行了直接等离子体脱硫脱硝和间接等离子体脱硫脱硝实验。在直接等离子体脱硫脱硝中,模拟烟气等混合气直接通入等离子体发生器,在反应器中电离分解NO以及和生成的高能电子、离子和自由基等离子体相互反应而进行脱除NO;间接等离子体脱硫脱硝中,模拟烟气连接在等离子体发生器出口与从反应器中产生出的等离子体发生氧化反应而进行脱除NO。结果表明,无论直接形式还是间接形式,脱硝效率都要比脱硫效率高,间接脱硫脱硝能够大大降低功率输入,节省能耗,具有重要的实际应用价值和意义。氨气的加入,有利于脱除效率的提升。