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Influence of Blade Outlet Angle on Inner Flow Field of Centrifugal Pump Transporting Salt Aqueous Solution

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 912-917页

作者： YANG Minguan KANG Can dong xiang LIU dong School of Energy and Power Engineering Jiangsu University Zhenjiang 212013 China

During transportation of salt aqueous solutions with centrifugal pump, crystallization phenomenon is frequently encountered. For this kind of two-phase flow, it is difficult to be accurately modeled since there are various medium properties and phase change characteristics. In view of experiment, several problems are hampering the implementation of precise measurement. Influences of blade outlet angle and medium temperature on crystallization rate were studied. Sodium sulfate solution was applied to simulate practical fluid in chemical industry. Particle image velocimetry（PIV） was employed to measure velocity distributions in rotating impeller. Crystallization processes in three impellers with different blade outlet angles were investigated. Relations among crystallization and flow parameters such as temperature and velocity were obtained. With the same blade wrap angle, when blade outlet angle is larger, diffusion of single flow passage gets stronger, relative velocity at blade outlet decreases and large scale vortex tends to appear near the blade working surface. For the impact of volume effect of particle phase on fluid viscosity, both liquid and solid phase velocities decrease with continual forming and growing of crystal particles. Velocity of solid phase is greater than that of liquid phase and its direction leans more closely to blade working surface. Solid particles tend to move towards blade working surface, as is more obvious in the impeller with large blade outlet angle. Therefore, collision between solid particles with stem part of blade working surface is more intensive in impeller with large blade outlet angle. Concerning transportation of salt aqueous solution, accurate PIV measurement is conducted in centrifugal impellers with different blade outlet angles. The results are useful and instructive in relevant engineering design and operation.

关键词： centrifugal pump flow with crystallization blade outlet angle particle image velocimetry(PIV)

Real-time in-situ monitoring of chiral changes during a reaction at single-molecule level

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Science China Chemistry 2024年第2期67卷 422-423页

作者： Min Tan dong xiang Institute of Modern Optics and Center of Single-Molecule Science Tianjin Key Laboratory of Micro-scale Optical Information Science and TechnologyNankai UniversityTianjin300350China School of Materials Science and Engineering Smart Sensing Interdisciplinary Science CenterNankai UniversityTianjin300350China TongLu FeiRan Garment–Nankai University Joint Laboratory Nankai UniversityTianjin300350China

Molecular chirality is a widespread phenomenon in nature,playing a critical role in various fields such as chemistry [1],life sciences [2], and materials science [3], and has therefore attracted significant attention and research by scholars [4–6].However, the chirality in chemical reactions is often dynamic, making real-time monitoring of chiral changes during chemical reactions at the single-molecule level extremely challenging.

关键词： chiral chirality critical

On the torque exerted by a warped, magnetically threaded accretion disk

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Research in Astronomy and Astrophysics 2021年第3期21卷 15-20页

作者： Chang Liu xiang-dong Li School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023

Most astrophysical accretion disks are likely to be *** X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the accretion *** have been extensive investigations on the accretion torque exerted by a coplanar disk that is magnetically threaded by the magnetic field lines from the neutron stars,but relevant works on warped/tilted accretion disks are still *** this paper we develop a simplified twocomponent model,in which the disk is comprised of an inner coplanar part and an outer,tilted *** on standard assumption on the formation and evolution of the toroidal magnetic field component,we derive the dimensionless torque and show that a warped/titled disk is more likely to spin up the neutron star compared with a coplanar *** also discuss the possible influence of various initial parameters on the torque.

关键词： accretion accretion disks magnetic field X-ray binaries

A Study of Magnetized White Dwarf+Helium Star Binary Evolution to Type Ia Supernovae

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Research in Astronomy and Astrophysics 2022年第2期22卷 1-15页

作者： Zhe Cui xiang-dong Li School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key Laboratory of Modern Astronomy and Astrophysics Nanjing UniversityMinistry of EducationNanjing 210023China

The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution have shown that the magnetic fields of WDs may significantly influence their accretion and nuclear burning *** this work we focus on the evolution of magnetized WD+He star binaries with detailed stellar evolution and binary population synthesis(BPS)*** the case of magnetized WDs,the magnetic fields may disrupt the inner regions of the accretion disk,funnel the accretion flow onto the polar caps and even confine helium burning within the *** find that,for WDs with sufficiently strong magnetic fields,the parameter space of the potential SN Ia progenitor systems shrinks toward shorter orbital periods and lower donor masses compared with that in the non-magnetized WD *** reason is that the magnetic confinement usually works with relatively high mass transfer rates,which can trigger strong wind mass loss from the WD,thus limiting the He-rich mass accumulation *** surviving companion stars are likely of low-mass at the moment of the SN explosions,which can be regarded as a possible explanation for the non-detection of surviving companions after the SNe or inside the SN ***,the corresponding birthrate of Galactic SNe Ia in our high-magnetic models is estimated to be~(0.08–0.13)×10^(-3)yr^(-1)(~0.17–0.28×10^(-3)yr^(-1)for the non-magnetic models),significantly lower than the observed Galactic SN Ia birthrate.

关键词： stars:evolution (stars:)supernovae:general–(stars:)binaries:general stars:magnetic field (stars:)white dwarfs

Immirzi parameter and quasinormal modes in four and higher spacetime dimensions

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Frontiers of physics 2016年第4期11卷 133-136页

作者： xiang-dong Zhang Department of Physics South China University of Technology Guangzhou 510641 China Institute for Quantum Gravity University of Erlangen-Nurnberg StaudtstraBe 7/ B2 91058 Erlangen Germany

There is a one-parameter quantization ambiguity in loop quantum gravity, which is called the Immirzi parameter. In this paper, we fix this free parameter by considering the quasinormal mode spectrum of black holes in four and higher spacetime dimensions. As a consequence, our result is consistent with the Bekenstein-Hawking entropy of a black hole. Moreover, we also give a possible quantum gravity explanation of the universal In 3 behavior of the quasinormal mode spectrum.

关键词： Immirzi parameter quasinormal mode loop quantum gravity

Non-coding RNA: a new frontier in regulatory biology

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National Science Review 2014年第2期1卷 190-204页

作者： xiang-dong Fu Department of Cellular and Molecular Medicine Institute of Genomic Medicine University of California

A striking inding in the past decade is the production of numerous non-coding RNAs(nc RNAs) from mammalian genomes. While it is entirely possible that many of those nc RNAs are transcription noises or by-products of RNA processing, increasing evidence suggests that a large fraction of them are functional and provide various regulatory activities in the cell. hus, functional genomics and proteomics are incomplete without understanding functional ribonomics. As has been long suggested by the ‘RNA world’hypothesis, many nc RNAs have the capacity to act like proteins in diverse biochemical processes. he enormous amount of information residing in the primary sequences and secondary structures of nc RNAs makes them particularly suited to function as scafolds for molecular interactions. In addition, their functions appear to be stringently controlled by default via abundant nucleases when not engaged in speciic interactions. his review focuses on the functional properties of regulatory nc RNAs in comparison with proteins and emphasizes both the opportunities and challenges in future nc RNA research.

关键词： the RNA world non-coding RNA biological functions regulatory mechanisms experimental approaches functional genomics

A Contact Force Model Considering Meshing and Collision States for Dynamic Analysisin Helical Gear System

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Chinese Journal of Mechanical Engineering 2019年第3期32卷 66-77页

作者： dong xiang Yinhua Shen Yaozhong Wei Department of Mechanical Engineering Tsinghua University

The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process of collision that often occurs in gear system. Focus on the contact-impact events, this paper proposes an improved gear contact force model for dynamic analysis in helical gear transmission system. In this model, a new factor associated with hysteresis damping is developed for contact-impact state, whereas the traditional linear damping factor is utilized for normal meshing state. For determining the selection strategy of these two damping factors, the fundamental contact mechanics of contact-impact event a ected by supporting forces are analyzed. During this analysis, an e ect factor is proposed for evaluating the influence of supporting forces on collision. Meanwhile, a new restitution of coe cient is deduced for calculating hysteresis damping factor, which suitable for both separation and non-separation states at the end of collision. In addition, the time-varying meshing sti ness(TVMS) is obtained based on the potential energy approach and the slice theory. Finally, a dynamic analysis of a helical gear system is carried out to better understand the contact force model proposed in this paper. The analysis results show that the contribution of supporting forces to the dynamic response of contact-impact event within gear pair is important. The supporting forces and dissipative energy are the main reasons for gear system to enter a steady contact state from repeated contact-impact state. This research proposes an improved contact force model which distinguishes meshing and collision states in gear system.

关键词： Contact-impact event Gear transmission Contact force Restitution coe cient Flexible support

Enzyme catalysis at single-molecule level

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Science China Chemistry 2023年第9期66卷 2441-2442页

作者： Surong Zhang dong xiang Institute of Modern Optics and Center of Single-Molecule Science Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology Nankai University Tianjin 300350 China School of Materials Science and Engineering Smart Sensing Interdisciplinary Science Center Nankai UniversityTianjin 300350 China TongLu FeiRan Garment-Nankai University Joint Laboratory Nankai University Tianjin 300350 China

Enzyme activity lays the foundation for the biochemical processes since the origin of life [1,2], and understanding the mechanism and kinetics of enzyme reactions is very important for the study of life science and bioengineering. The ensemble-averaged experiments are unable to characterize the transient intermediates or various specific steps during the catalytic cycle of enzymes, which brings a challenge to reveal enzyme-catalytic mechanisms. Now, in the article published in the Nature Catalysis, Prof. Wenjing Hong, *** Fang and Prof. Binju Wang in Xiamen University employed a scanning tunneling microscope-break junction technique (STM-BJ) with a time resolution of milli-second to probe the stepwise reaction dynamics of the catalytic cycle at the single-enzyme leve.

关键词： catalysis Xiamen kinetics

Measure of Noncompactness and Semilinear Nonlocal Functional Differential Equations in Banach Spaces

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Acta Mathematica Sinica,English Series 2015年第1期31卷 140-150页

作者： Qi xiang dong Gang LI School of Mathematical Sciences Yangzhou University

This paper is concerned with the measure of noncompactness in the spaces of continuous functions and semilinear functional differential equations with nonloeal conditions in Banach spaces. The relationship between the Hausdorff measure of noncompactness of intersections and the modulus of equicontinuity is studied for some subsets related to the semigroup of linear operators in Banach spaces. The existence of mild solutions is obtained for a class of nonlocal semilinear functional differential equations without the assumption of compactness or equicontinuity on the associated semigroups Of linear operators.

关键词： Measure of noncompactness equicontinuity differential equation nonlocal condition C0-semigroup mild solution