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Experiment Study on Active-passive Mode-locking Using Cr4+∶YAG as Saturable Absorber

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Chinese Journal of Lasers 2002年第1期11卷 2-5页

作者： LENG Yuxin LU Haihe LIN Lihuang XU Zhizhan (shanghai institute of Optics and Fine {2., The Chinese Academy of Sciences, shanghai 2.1800, china) shanghai institute of Optics and Fine {2. The Chinese Academy of Sciences 上海 201800

Cr 4+ ∶YAG crystal was used as a saturable absorber in an active-passive mode-locked Nd∶YAG laser. The stable and complete mode-locked pulse train was achieved at 1064 nm. The duration of ～0.8 ns to 2.4 ns for a single pulse was obtained by using Cr 4+ ∶YAG crystals with the different initial transmissions, and there was a shortest pulse width. The mode-locking dynamic process of Cr 4+ ∶YAG crystal was discussed to explain the experimental result, and the effect of excited-state absorption was considered.

关键词： Cr 4+ ∶YAG active-passive mode-locking excited-state absorption

NUMERICAL ANALYSIS OF THE 3-D FLOW FIELD OF PRESSURE ATOMIZERS WITH V-SHAPED CUT AT ORIFICE

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Journal of Hydrodynamics 2011年第2期23卷 187-192页

作者： ZHOU Hua School of Aerospace Engineering and applied mechanics Tongji University Shanghai 200092 China

Axisymmetric liquid jets have been studied extensively for more than one century, while non-axisymmetric jets are also very common in engineering applications but attract less concern. Based on Eulerian fluid-fluid model in Fluent software, this article analysizes the 3-D flow fields of pressure atomizers with V-shaped cut at orifice, which will result in a non-axisymmetric liquid jet. Flow rate analysis and jet structure analysis are carried out, the results show that the flow rate can be formulated by adding a correction coefficient to the formula of inviscid axisymmetric jets in atomization regime, when the Weber number is low enough to make the flow fall out of atomization regime, and the jet structure together with the flow rate formula will change. Analysis shows that the evolution of the spray and therefore the structure of the liquid jet are affected much by relative velocity and the local volume fraction of liquid phase.

关键词： flow rate fraction distribution gas-liquid interference non-axisymmetric liquid jet pressure atomizer

A generalized wave action conservative equation for the dissipative dynamical system in the nearshore region

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Progress in Natural Science:Materials International 2003年第7期 72-74页

作者： HUANG Hu (1. shanghai institute of {2. mathematics and mechanics, shanghai University, shanghai 2.0072. china 2. LNM, institute of mechanics, Chinese Academy of Sciences, Beijing 100080, china)

To describe the various complex mechanisms of the dissipative dynamical system between waves, currents, and bottoms in the nearshore region that induce typically the wave motion on large-scale variation of ambient currents, a generalized wave action equation for the dissipative dynamical system in the nearshore region is developed by using the mean-flow equations based on the Navier-Stokes equations of viscous fluid, thus raising two new concepts: the vertical velocity wave action and the dissipative wave action, extending the classical concept, wave action, from the ideal averaged flow conservative system into the real averaged flow dissipative system (that is, the generalized conservative system). It will have more applications.

关键词： dissipative dynamical system wave action conservation the averaged flow equations the Navier-Stokes equations.

EXPERIMENTAL INVESTIGATION ON THE DRAG REDUCTION CHARACTERISTICS OF TRAVELING WAVY WALL AT HIGH REYNOLDS NUMBER IN WIND TUNNEL

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Journal of Hydrodynamics 2010年第5期22卷 719-724页

作者： YAO Yan LU Chuan-jing SI Ting ZHU Kun Department of Engineering mechanics Shanghai Jiao Tong University Shanghai 200240 China Beijing Electromechanic Engineering institute Beijing 100074 China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai 200030 China Department of Modern mechanics University of Science and Technology of China Hefei 230027 China

Drag reduction experiments of the traveling wavy wall at high Reynolds number, ranging from 1.46×106 to 5.83×106 based on the free-stream velocity and the model length, were conducted. A suit of traveling wavy wall device was developed and its characteristics of drag reduction at high Reynolds number were investigated. The drag forces of the traveling wavy wall with various wave speeds （ c ） were measured at different wind speeds （U ） in the FL-8 low-speed wind tunnel and compared with the drag force of the flat plate. The results show that the mean drag force of the traveling wavy wall decreases as the value of c /U increases, at different wind velocities, the values of c /U corresponding to minimal drag force of the traveling wavy wall are different, when the values of c /U are larger than 0.6, the mean drag forces of the traveling wavy wall are smaller than those of the flat plate, and the drag reduction can be up to 60%. The drag reduction effectiveness of traveling wavy wall is thus achieved. Furthermore, as the value of c /U increases, the traveling wavy wall can restrain the separation and improve the quality of flow field.

关键词： flow control drag reduction traveling wavy wall wind tunnel test

Lagrangian time scales and its relationship to Eulerian equivalents in turbulent channel flow

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Journal of shanghai University(English Edition) 2010年第1期14卷 71-75页

作者：罗剑平卢志明刘宇陆 School of Mechanical and Automation Engineering Shanghai Institute of Technology shanghai institute of {2. mathematics and mechanics Shanghai University

Lagrangian and Eulerian time scales were obtained from the direct numerical simulation of turbulent channel flow at two Reynolds numbers based on the friction velocity and channel half-height, Rer= 80, 100. The Lagrangian integral time scales and time microscales were compared to their Eulerian equivalents. It is found that the ratio of Lagrangian to TL Eulerian integral time scales is given by TE/TiE= 1 ＋ 0.1y＋ for y＋ ≤ 10, and that the ratios between the Lagrangian to theEulerian time microscales are almost the same irrespective of the components. Those increase with y＋ are approximated by ≈ 2.75 - 1.75 exp （-v＋/a） . These results also show that these expressions are independent of the Reynolds number.

关键词： turbulent channel flow Lagrangian time scale Eulerian time scale direct numerical simulation (DNS)

Propagation and Beam Quality of Flattened Hermite-Gauss Beams

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Chinese Journal of Lasers 1995年第2期B4卷 127-132页

作者： HUA Renzhong QIAN Liejia, FAN Dianyuan DENC Ximing(shanghai institute of Optics and Fine {2., Academia Sinica,shanghai 2.1800, china) shanghai Inst of Optics and Fine Mechanics Shanghai China

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ＰｒｏｐａｇａｔｉｏｎａｎｄＢｅａｍＱｕａｌｉｔｙｏｆＦｌａｔｔｅｎｅｄＨｅｒｍｉｔｅ－ＧａｕｓｓＢｅａｍｓ￥ＨＵＡＲｅｎｚｈｏｎｇ；ＱＩＡＮＬｉｅｊｉａ，ＦＡＮＤｉａｎｙｕａｎ；ＤＥＮＣＸｉｍｉｎｇ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｐｔｉｃ...

关键词： beam propagation beam quality flattened Hermite-Gauss beam

THE VOF METHOD FOR STUDY OF WAVE RUN-UP AND BREAKING ON A SLOPING STRUCTURE

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Journal of Hydrodynamics 1997年第4期9卷 88-96页

作者： Wan De-chengshanghai institute of {2. mathematics, and mechanics shanghai University,shanghai2.0072. P. R. china.Miao Guo-pingDepartment of Naval Architecture and Ocean Engineering, shanghai Jiao Tong University,shanghai 2.0030,P. R. china.Dai Shi-qiangshanghai institute of {2. mathematics and mechanics, shanghai University,shanghai2.0072. P. R. china.

The volume of fluid method (VOF method) for numerical simulations describing wave run-up on a sloping structure including the overturning. breaking and merging phenomena is presented. The flow motions are governed by the classical, two-dimensional Navier-Stokes equation for incompressible fluid. Computational results concerning the time evolution of the free surface and pressure distribution along water bed and slope boundary are given, showing how an initial solitary wave undergoes run-up, overturning, breaking and merging on the slope. It is found that most of the wave energy is lost after the wave breaking and merging.

关键词： VOF method wave run-up wave breaking sloping structure

Exact Solution to(1+1)-Dimensional Higher-Order SchrSdinger Equation via an Extended Mapping Approach

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Communications in Theoretical Physics 2006年第1期45卷 127-130页

作者： ZHU Hai-Ping~1 ZHENG Chun-Long~(1,2.+) FANG Jian-Ping~11 Department of Physics,Zhejiang Lishui University,Lishui 32.000,china2.shanghai institute of applied mathematics and mechanics,{2. University,{2. 2.0072.china

Starting from a special variable transformation and with the help of an extended mapping approach,the high-order Schr■dinger equation(n=3,4)is solved.A new family of variable separation solutions with arbitraryfuncti... 详细信息

关键词： extended mapping approach Schr■dinger equation exact solution

Tracheal compliance and limit flow rate changes in a murine model of asthma

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Science china(Life Sciences) 2008年第10期51卷 922-931页

作者： TENG ZhongZhao1, WANG YiQin2. LI FuFeng2. YAN HaiXia2.& LIU ZhaoRong3 1 Department of Mathematical Sciences, Worcester Polytechnic institute, Worcester, MA, 01609, USA 2.Syndrome Laboratory of TCM, shanghai University of Traditional Chinese Medicine, shanghai 2.12.3, china 3 Department of mechanics and Engineering Science, Fudan University, shanghai 2.0433, china 1. Department of Mathematical Sciences Worcester Polytechnic Institute Worcester MA 01609 USA 2. Syndrome Laboratory of TCM Shanghai University of Traditional Chinese Medicine Shanghai 201203 China 3. Department of mechanics and Engineering Science Fudan University Shanghai 200433 China

Trachea is the unique passage for air to flow in and out. Its tone is of importance for the respiration system. However, investigation on how tracheal tone changes due to asthma is limited. Aiming at studying how the mechanical property changes due to asthma as well as the compliance and flow limitation, the following methods are adopted. Static and passive pressure-volume tests of rats' trachea of the asthmatic and control groups are carried out and a new type of tube law is formulated to fit the experimental data, based on which changes of compliance and limit flow rate are investigated. In order to give explanation to such changes, histological examinations with tracheal soft tissues are made. The results show that compliance, limit flow rate and material constants included in the tube law largely depend on the longitudinal stretching ratio. Compared with the control group, the tracheal compliance of asthmatic animals decreases significantly, which results in an increased limit flow rate. Histological studies indicate that asthma can lead to hyperplasia/hypertrophy of smooth muscle cells, and increase elastin and collagen fibres in the muscular membrane. Though decreasing compliance increases sta- bility, during the onset of asthma, limit flow rate is much smaller due to the lower transmural pressure. Asthma leads to a stiffer trachea and the obtained results reveal some aspects relevant to asthma-induced tracheal remodelling.

关键词： trachea asthma collapse tube law compliance limit flow rate remodelling