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Adiabatic regularization and Green's function of a scalar field in de Sitter space: Positive energy spectrum and no trace anomaly

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Science China(Physics,Mechanics & Astronomy) 2020年第5期63卷 59-91页

作者： Yang Zhang xuan ye Bo Wang Department of Astronomy Key Laboratory for Researches in Galaxies and CosmologySchool of Astronomy and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

In the conventional adiabatic regularization the vacuum ultraviolet divergences of a quantum field in curved spacetime are removed by subtracting the k-mode of the stress tensor to the 4 *** a scalar field in de Sitter space,we find that the4 th-order regularized spectral energy density is ***,the 2 nd-order regularization for minimal coupling(ξ=0)and the 0 th-order regularization for conformal coupling(ξ=1/6) yield a positive and UV-convergent spectral energy density and power *** regularized stress tensor in the vacuum is maximally symmetric and can drive inflation,while its k-modes representing the primordial fluctuations are nonuniformly *** regularization of a Green's function in position space is generally plagued by a log IR *** in the massless case with ξ=0 or 1/6,we can directly regularize the Green's functions and obtain vanishing results that agree with the adiabatic regularization *** this case,the regularized power spectrum and stress tensor are both zero,and no trace anomaly *** overcome the log IR divergence problem in the massive cases with ξ=0 and 1/6,we perform Fourier transformation of the regularized power spectra and obtain the regularized analytical Green's functions which are IR-and UV-convergent.

关键词： inflationary universe mathematical and relativistic aspects of cosmology quantum fields in curved spacetimes

A Review on Vibration Control of Multiple Cylinders Subjected to FlowInduced Vibrations

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China Ocean Engineering 2024年第2期38卷 183-197页

作者： XU Wan-hai MA ye-xuan State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300350China Institute of Mechanics Chinese Academy of SciencesBeijing 100190China

The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering *** FIV suppression is of great importance for the security of many cylindrical *** active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated *** to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV *** efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two *** control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control *** FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and *** FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence *** research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.

关键词： flow-induced vibration vibration control multiple cylinders tandem side-by-side staggered

Hydrolysis of epoxides and aziridines catalyzed by polymer-supported quarternary ammonium bisulfate

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Chinese Chemical Letters 2008年第2期19卷 146-148页

作者： Wan xuan Zhang Kang ye Ministry-of-Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules Hubei University Wuhan 430062 China

Macroporous resin （D201）-supported quartemary ammonium bisulfate （D201-HSO4） was prepared and effectively used in catalyzing the hydrolysis of epoxides or aziridines under mild and non-metal conditions to give the... 详细信息

关键词： Resin-supported quartemary ammonium bisulfate Catalysis Hydrolysis Aziridine Epoxide

New era of drug innovation in China

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Acta Pharmaceutica Sinica B 2019年第5期9卷 1084-1085页

作者： xuan ye Qingli Wang Haixue Wang Office of Pharmacology and Toxicology Center for Drug Evaluation National Medical Products Administration

In 2018, the China National Medical Products Administration(NMPA) approved new drug applications (NDAs) of 48 new drugs, which was the highest annual approval rate by the Chinese regulatory agency in the past 20 years. Nine of the 48 new drugs,including fruquintinib, anlotinib, toripalimab and sintilimab, are global new molecular entities (NME) that were developed by Chinese pharmaceutical companies.

关键词： New era drug innovation China

Tensile properties of individual multicellular Bacillus subtilis fibers

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Science China(Physics,Mechanics & Astronomy) 2019年第9期62卷 70-78页

作者： xuan ye Tao Wang Zhuo Zhuang XiDe Li Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing 100084China Center for Nano and Micro Mechanics Tsinghua UniversityBeijing 100084China

Microfibers formed by Bacillus subtilis(B. subtilis) have attracted interest because of their potential for use as biodegradable fibers. In this work, an efficient method based on the micro-liquid bridge method(LBM) is proposed to investigate the mechanical properties and the deformation evolution in individual fibers. For the first time, tensile testing of fibers of this type containing several cells is conducted in a scanning electron microscope(SEM) chamber and the in situ deformation evolution of the fibers and the septa is observed. Experimental results show that these fibers are almost broken at the positions of the septa at low humidity, but also show that their fracture morphologies are different. At high humidity, local necking deformation occurs at the septum position. To explore the deformation mechanism of an individual bacterial fiber with a diameter of several hundred nanometers under different humidity conditions, we use the finite element method(FEM) to analyze the tensile deformation behavior of these fibers when their septa are at various separation levels. The numerical results indicate that weak interactions among the septa lead to the dispersion of both the fibrous tensile strength and the modulus. These results may be helpful in understanding the deformation mechanism, thus leading to further improvements in the mechanical performance of these fibers.

关键词： Bacillus subtilis mechanical properties micro-liquid bridge method finite element method

Hedgehog signaling:mechanisms and evolution

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Frontiers in Biology 2011年第6期6卷 504-521页

作者： xuan ye Aimin LIU Department of Biology Eberly College of ScienceThe Pennsylvania State UniversityUniversity ParkPA 16802USA

The Hedgehog(Hh)family of secreted proteins plays essential roles in the development of a wide variety of animal species and underlies multiple human birth defects and *** ensure the proper range of signaling,the Hh proteins are modified with lipids,assembled into water-soluble multimers,and interact with multiple cell surface *** the target cells,a largely conserved intracellular signal transduction pathway,from the cell surface receptor Patched to the Glioma-associated oncogene homolog(Gli)family of transcription factors,mediates the transcriptional responses from fruit flies to mammals.A significant divergence between vertebrates and insects is the vertebrate-specific requirement of cilia for Hh signal transduction and Gli protein ***,transcription-independent cellular responses to Hh have been described in certain developmental *** clinical trial underway to treat Hhrelated diseases,more work is urgently needed to reach a more comprehensive understanding of the molecular mechanisms underlying the regulation of Hh signaling in development and diseases.

关键词： Hedgehog Shh Ihh Dhh Cubitus interruptus(Ci) Gli1 Gli2 Gli3 Patched Smoothened Cilia Drosophila mouse signaling development evolution

A massless scalar field in Robertson-Walker spacetimes:Adiabatic regularization and Green’s function

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Chinese Physics C 2020年第9期44卷 194-209页

作者： Yang Zhang Bo Wang xuan ye Department of Astronomy CAS Key Laboratory for Researches in Galaxies and CosmologySchool of Astronomy and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

We study adiabatic regularization of a coupling massless scalar field in general spatially flat Robertson-Walker(RW)*** the conformal coupling,the 2nd-order regularized power spectrum and 4th-order regularized stress tensor are zero,and no trace anomaly exists in general RW *** is a new result that exceeds those found in de Sitter *** the minimal coupling,the regularized spectra are also zero in the radiationdominant and matter-dominant stages,as well as in de Sitter *** vanishing of these adiabatically regularized spectra is further confirmed by direct regularization of the Green's *** a general coupling and general RW spacetimes,the regularized spectra can be negative under the conventional *** a higher order of regularization,the spectra will generally become positive,but will also acquire IR divergence,which is inevitable for a massless *** avoid the IR divergence,the inside-horizon regularization is *** these procedures,nonnegative UV-and IR-convergent power spectrum and spectral energy density will eventually be achieved.

关键词： quantum fields in curved spacetimes inflationary universe mathematical and relativistic aspects of cosmology

Vortex-Induced Vibration Response Features of A Submarine Multi-Span Pipeline via Towing Tank Experimental Tests

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China Ocean Engineering 2023年第2期37卷 175-189页

作者： XU Wan-hai JIA Kun MA ye-xuan SONG Zhi-you State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the structural vibration characteristics more complex, which may change the fatigue characteristics of the pipeline and affect the safety of the structure. In this paper, model tests were designed to explore the vortex-induced vibration(VIV) characteristics of multi-span pipelines and investigate the multi-span interaction mechanism. The experimental study mainly focused on the dynamic response of double-span pipelines, and further extended to triple-span pipelines, hoping that the results can be applied to more complex environment. The effects of span-length ratio, buried depth and axial force on VIV of the pipeline were investigated and discussed. The dynamic response of the pipeline varied with the span length. There was obvious interaction between different spans of multi-span pipelines, and the pipe-sediment interaction obviously affected the vibration characteristics of pipeline. The differences of pipeline burial depth and axial force changed the structural stiffness. With the increase of buried depth, the response amplitude presented a downward trend. The spanwise evolutions were asymmetric caused by the pipe-sediment interaction and multi-span interaction. The results can help to identify multi-span pipelines in engineering, and realize the prevention and control of free spans.

关键词： vortex-induced vibration submarine pipeline pipe-sediment interaction multi-span interaction

Displacement Response Reconstruction of Slender Flexible Structures Based on Cubic Spline Fitting Method

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China Ocean Engineering 2019年第2期33卷 226-236页

作者： HAN Qing-hua MA ye-xuan FENG Xin-xin XU Wan-hai State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University School of Civil Engineering Tianjin University

How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring(SHM), which are beneficial for controlling the structural vibration and protecting the structural safety. In this paper, the displacement reconstruction method based on cubic spline fitting is put forward to reconstruct the dynamic displacement of slender flexible structures without the knowledge of modeshapes and applied loading. The obtained strains and displacements are compared with the results calculated by ABAQUS to check the method's validity. It can be found that the proposed method can accurately identify the strains and displacement of slender flexible structures undergoing linear vibrations, nonlinear vibrations, and parametric vibrations. Under the concentrated force, the strains of slender flexible structures will change suddenly along the axial direction. With locally densified measurement points, the present reconstruction method still works well for the strain concentration problem.

关键词： displacement reconstruction cubic spline fitting slender flexible structures linear vibrations parametric vibrations nonlinear vibrations