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Isometries on the Quasi-Banach Spaces L^p (0 < p <1)

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Acta Mathematica Sinica,English Series 2010年第8期26卷 1519-1524页

作者： Lei LI Wei yun ren School of Mathematical Sciences and LPMC Nankai University Tianjin 300071 P. R. China Department of Mathematics School of Sciences Tianjin University Tianjin 300072 P. R. China

We study the extension of isometries between the unit spheres of quasi-Banach spaces Lp for 0〈p〈1. We give some sufficient conditions such that an isometric mapping from the the unit sphere of Lp（μ） into that of ... 详细信息

关键词： Quasi-Banach spaces isometric mappings unit spheres

Frequency invariability of acoustic field and passive source range estimation in shallow water

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Science China(Physics,Mechanics & Astronomy) 2014年第2期57卷 225-232页

作者： ZHOU ShiHong QI YuBo ren yun State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of Sciences

The frequency invariability of the warped modal signal and the warped signal autocorrelation function in shallow water is discussed.A method is proposed for passive source-range estimation based on the frequency invariability and warping transform of signal autocorrelation function received by a single hydrophone in a range-independent or weak range-dependent shallow water *** the method,a guided source with a known range is employed to provide the crucial and relative invariant scaled *** experimental data in shallow water with an iso-speed profile and a fluctuated thermocline are used to verify this *** relative errors of the source range estimation are basically less than 10%.

关键词： frequency invariability warping transform autocorrelation function passive range estimation single hydrophone

NUMERICAL SIMULATION OF UNSTEADY FLOW FOR VISCO- ELASTIC FLUID IN AN ECCENTRIC ANNULUS WITH INNER ROD RECIPROCATION

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Journal of Hydrodynamics 2008年第2期20卷 261-266页

作者： HE Feng-yun YANG Shu-ren Department of Petroleum Engineering Daqing Petroleum Institute Daqing 163318 China

The equation governing the unsteady flow of viscoelastic fluids in an eccentric annulus was derived by using the common conversion Maxwell fluid constitutive equation and then discretized by the control volume method. The velocity distribution of flow field was computed by using the ADI method. The influences of the pressure gradient, eccentricity, stroke length, and stroke frequency on the velocity and flow capacity in the flow field was analyzed. The foundation for further research of the eccentric wear problem of the pumping rod in polymer-flood well was laid.

关键词： polymer-flood well viscoelastic fluid eccentric annulus unsteady flow eccentric wear

Unsteady Flow and Structural Behaviors of Centrifugal Pump under Cavitation Conditions

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Chinese Journal of Mechanical Engineering 2019年第1期32卷 127-141页

作者： Denghao Wu yun ren Jiegang Mou yunqing Gu Lanfang Jiang College of Mechanical Engineering Zhejiang University of Technology Zhijiang College Zhejiang University of Technology

Cavitation has a significant e ect on the flow fields and structural behaviors of a centrifugal pump. In this study, the unsteady flow and structural behaviors of a centrifugal pump are investigated numerically under di erent cavitation conditions. A strong two-way coupling fluid-structure interaction simulation is applied to obtain interior views of the e ects of cavitating bubbles on the flow and structural dynamics of a pump. The renormalization-group k-ε turbulence model and the Zwart–Gerbe–Belamri cavitation model are solved for the fluid side, while a transient structural dynamic analysis is employed for the structure side. The di erent cavitation states are mapped in the head-net positive suction head(H-NPSH) curves and flow field features inside the impeller are fully revealed. Results indicate that cavitating bubbles grow and expand rapidly with decreasing NPSH. In addition, the pressure fluctuations, both in the impeller and volute, are quantitatively analyzed and associated with the cavitation states. It is shown that influence of the cavitation on the flow field is critical, specifically in the super-cavitation state. The e ect of cavitation on the unsteady radial force and blade loads is also discussed. The results indicate that the averaged radial force increased from 8.5 N to 54.4 N in the transition progress from an onset cavitation state to a super-cavitation state. Furthermore, the structural behaviors, including blade deformation, stress, and natural frequencies, corresponding to the cavitation states are discussed. A large volume of cavitating bubbles weakens the fluid forces on the blade and decreases the natural frequencies of the rotor system. This study could enhance the understanding of the e ects of cavitation on pump flow and structural behaviors.

关键词： Centrifugal pump Cavitation Unsteady flow Structural behaviors Fluid-structure interaction

Enhancement of Flow Boiling Heat Transfer with Surfactant

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Journal of Central South University 2000年第4期12卷 219-222页

作者： QIU yun-ren CHEN Wei-ping SI Qin College of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China Editorial Office of Journal of Central South University of Technology Central South UniversityChangsha 410083China College of Chemical Engineering Tianjin UniversityTianjin 300072China

The surfactant additive octadecylamine (ODA) was used to enhance the flow boiling heat transfer of water in vertical copper tube, and the effects of the aqueous solution properties, mass fraction of ODA, mass flux and heat flux etc. on flow boiling heat transfer were investigated. In order to analyze the mechanism of enhancement on boiling heat transfer with ODA, the copper surface was detected by XPS, and the diagram of binding energy was obtained. The results show that ODA can be adsorbed on the surface of the copper wall, and affects the properties of the heating surfaces and enhances the flow boiling heat transfer of water. Only in low heat flux and in a suitable range of concentration, can ODA aqueous solution enhance flow boiling heat transfer, and the suitable mass fraction of ODA is in the range of 1×10 -5 5×10 -5 . In addition, compared with water, ODA aqueous solution does not increase the flow drag under the same experimental conditions.

关键词： flow boiling heat transfer flow drag enhancement additive

Stability and a fast calculation method of travel speed of pulse peak in convergence zone

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Science China(Physics,Mechanics & Astronomy) 2014年第7期57卷 1274-1282页

作者： ren yun ZHANG renHe WANG Jun GUO YongGang Luo WenYu State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences

A long-range sound propagation experiment was conducted in the West Pacific Ocean in summer *** signals received by a towed array indicate that the travel speed of pulse peak(TSPP)in the convergence zones is ***,an equivalent sound speed can be used at all ranges in the convergence zones.A fast calculation method based on the beam-displace-ment ray-mode(BDRM)theory and convergence zone theory is proposed to calculate this equivalent sound *** computation speed of this proposed method is over 1000 times faster than that of the conventional calculation method based on the normal mode theory,with the computation error less than 0.4%compared with the experimental ***,the effect of frequency and sound speed profile on the TSPP is studied with the conventional and fast calculation methods,showing that the TSPP is almost independent of the frequency and sound speed profile in the ocean surface layer.

关键词： travel speed pulse peak pulse propagation BDRM theory turning point convergence zone

CFD Investigation of the Influence of Volute Geometrical Variations on Hydrodynamic Characteristics of Circulator Pump

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Chinese Journal of Mechanical Engineering 2016年第2期29卷 315-324页

作者： WU Denghao YUAN Shouqi ren yun MU Jiegang YANG Youdong LIU Jian Zhijiang College Zhejiang University of Technology College of Mechanical Engineering Zhejiang University of Technology Research Center of Fluid Machinery Engineering and Technology Jiangsu University

Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic

关键词： CFD circulator pump hydrodynamic characteristics volute variations

First synthesis and characterization of key stereoisomers related to Ezetimibe

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Chinese Chemical Letters 2014年第8期25卷 1157-1160页

作者： yun ren Yan-Jun Duan ren-Jun Li Yong Deng Li Hai Yong Wu Key Laboratory of Drug Targeting and Drug Delivery System of the Education Ministry Department of Medicinal Chemistry West China School of PharmacySichuan University

uring the laboratory optimization and the late phase manufacturing studies of the cholesterol absorption inhibitor Ezetimibe 1, the formation of several stereoisomers was observed. To study the complete stereoisomer profile of Ezetimibe 1, we have synthesized and completely characterized several key stereoisomers of Ezetimibe 1 for the first time. This study will provide an access to the reference standard of these stereoisomers and may have some implications in the development of new medicines.

关键词： Ezetimibe Related substances Stereoisomers profile Synthesis Characterization

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非均匀强激光场下正负电子对的产生

原子与分子物理学报 2025年第2期42卷 117-123页

作者：落彩青任云亮吾拉依木江·司提瓦力地新疆大学物理科学与技术学院乌鲁木齐830046

随着强激光技术领域的不断突破,使得能量转化成物质的施温格过程的实验指日可待.在这样的背景下,在接近实际强激光的模型中理论研究施温格效应至关重要.本文采用量子场论模拟方法在非均匀电场中研究施温格效应的空间特性.首先,发现在能... 详细信息

随着强激光技术领域的不断突破,使得能量转化成物质的施温格过程的实验指日可待.在这样的背景下,在接近实际强激光的模型中理论研究施温格效应至关重要.本文采用量子场论模拟方法在非均匀电场中研究施温格效应的空间特性.首先,发现在能量保持不变的情况下电场的空间尺度显著影响正负电子对的产生率、动量和空间分布.正负电子对的动量和空间分布显示,当电场的空间尺度增大时,因为电场强度变小,所以产生的正负电子对无法及时被分开,抑制正负电子对的产生.最后,用连续性方程研究正负电子对的产生位置分布,发现正负电子对的产生位置分布与电场强度分布是对应的,电子和正电子的产生位置分离一个康普顿波长.此研究结果展示了施温格效应的空间特性,同时解释了弱电场下施温格效应的抑制机制.这些结论在人们常采用的均匀电场近似研究中无法得到.我们的研究对检测施温格实验中的正负电子对具有重要的指导意义.

关键词：强激光施温格效应量子场论模拟方法非均匀电场空间分布

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