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| 1 | Supersonic flow imaging via nanoparticles显示文摘Due to influence of compressibility,shock wave,instabilities,and turbulence on supersonic flows, current flow visualization and imaging techniques encounter some problems in high spatiotemporal resolution and high signal-to-noise ratio(SNR)measurements.Therefore,nanoparticle based planar laser scattering method(NPLS)is developed here.The nanoparticles are used as tracer,and pulse planar laser is used as light source in NPLS;by recording images of particles in flow field with CCD, high spatiotemporal resolution supersonic flow imaging is realized.The flow-following ability of nanoparticles in supersonic flows is studied according to multiphase flow theory and calibrating experiment of oblique shock wave.The laser scattering characteristics of nanoparticles are analyzed with light scattering theory.The results of theoretical and experimental studies show that the dynamic behavior and light scattering characteristics of nanoparticles highly enhance the spatiotemporal resolution and SNR of NPLS,with which the flow field involving shock wave,expansion,Mach disk,boundary layer,sliding-line,and mixing layer can be imaged clearly at high spatiotemporal resolution. | ZHAO YuXin YI ShiHe TIAN LiFeng CHENG ZhongYu | 2009 | Science China(Technological Sciences)2009，52，12： | 31 |
| 2 | The fractal measurement of experimental images of supersonic turbulent mixing layer显示文摘Flow visualization of supersonic mixing layer has been studied based on the high spatiotemporal resolution Nano-based Planar Laser Scattering(NPLS) method in SML-1 wind tunnel. The corresponding images distinctly reproduced the flow structure of laminar,transitional and turbulent region,with which the fractal measurement can be implemented. Two methods of measuring fractal dimension were introduced and compared. The fractal dimension of the transitional region and the fully developing turbulence region of supersonic mixing layer were measured based on the box-counting method. In the transitional region,the fractal dimension will increase with turbulent intensity. In the fully developing turbulent region,the fractal dimension will not vary apparently for different flow structures,which em-bodies the self-similarity of supersonic turbulence. | ZHAO YuXin YI ShiHe TIAN LiFeng HE Lin CHENG ZhongYu | 2008 | Science China(Physics,Mechanics & Astronomy)2008，51，8： | 24 |
| 3 | Aero-optical aberration measuring method based on NPLS and its application显示文摘The existing methods for measuring aero-optical aberration suffer from several problems,such as low spatiotemporal resolution,sensitivity to environment,and integral effects.A new method for measuring aero-optical aberration of supersonic flow is proposed.Based on the self-developed measuring method of supersonic density field,the wavefront aberration induced by a cross-section of supersonic flow field could be measured by ray-tracing.Compared with other methods,the present one has three significant innovations:(1) high spatiotemporal resolution.Its time resolution is 6 ns,and the spatial resolution can reach up to micrometers;(2) it can avoid the integral effects and study the wavefront aberration induced by the flow field of interest locally;(3) it can also avoid the influence from the test section wall boundary layers and environmental disturbances.The present method was applied to supersonic flow around an optical bow cap.The results of high spatiotemporal resolution reveal fine wavefront structures,and show that shock waves,expansion waves and turbulent boundary layers have different impacts on the wavefront aberration. | YI ShiHe TIAN LiFeng ZHAO YuXin HE Lin CHEN Zhi | 2010 | Chinese Science Bulletin2010，55，31： | 20 |
| 4 | Visualization of coherent structures in a supersonic flat-plate boundary layer显示文摘Flow in a flat-plate zero-pressure-gradient boundary layer at Mach 3 was visualized via nanoparticle-based planar laser scattering (NPLS). Coherent structures such as an individual hairpin vortex and hairpin packet were identified in the streamwise-wall-normal plane on the basis of the now accepted hairpin model. Λ-shaped vortices were found in a staggered pattern in the stream-wise-spanwise plane, which indicated H-type transition in the present experiments. This is the direct evidence (in the form of flow visualization) of such coherent structures in a supersonic boundary layer. A series of NPLS images taken in streamwise-spanwise planes at different heights is presented, and the three-dimensional structures of the supersonic boundary layer agree well with the hairpin model. | HE Lin YI ShiHe ZHAO YuXin TIAN LiFeng CHEN Zhi | 2011 | Chinese Science Bulletin2011，56，6： | 19 |
| 5 | The experimental study of interaction between shock wave and turbulence显示文摘The interaction between shock wave and turbulence has been studied in supersonic turbulent mix layer wind tunnel. The interaction between oblique shock wave and turbulent boundary layer and the influence of large vortex in mix layer on oblique shock wave have been observed by NPLS technique. From NPLS image, not only complex flow structure is observed but also time-dependent supersonic flow visualization is realized. The mechanism of interaction between shock wave and turbulence is discussed based on high quality NPLS image. | ZHAO YuXin YI ShiHe HE Lin CHENG ZhongYu TIAN LiFeng | 2007 | Chinese Science Bulletin2007，52，10： | 18 |
| 6 | Study of density field measurement based on NPLS technique in supersonic flow显示文摘Due to the influence of shock wave and turbulence, supersonic density field exhibits strongly inhomogeneous and unsteady characteristics. Applying traditional density field measurement techniques to supersonic flows yields three problems: low spatiotemporal resolution, limitation of measuring 3D density field, and low signal to noise ratio (SNR). A new method based on Nano-based Planar Laser Scattering (NPLS) technique is proposed in this paper to measure supersonic density field. This method measures planar transient density field in 3D supersonic flow by calibrating the relationship between density and concentration of tracer particles, which would display the density fluctuation due to the influence of shock waves and vortexes. The application of this new method to density field measurement of supersonic optical bow cap is introduced in this paper, and the results reveal shock wave, turbulent boundary layer in the flow with the spatial resolution of 93.2 μm/pixel. By analyzing the results at interval of 5 μs, temporal evolution of density field can be observed. | TIAN LiFeng YI ShiHe ZHAO YuXin HE Lin CHENG ZhongYu | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，9： | 15 |
| 7 | An experimental study of aero-optical aberration and dithering of supersonic mixing layer via BOS显示文摘The optical performance of supersonic mixing layer is heavily deteriorated by the aero-optical aberration and dithering of coherent structures, but current measuring methods limit the spatiotemporal resolution in relevant studies. A high resolution whole-field aero-optical aberration and dithering measuring method based on the Background Orient Schlieren (BOS) technique was studied. The systematic structure, sensitivity and resolution of BOS are analyzed in this paper. The aero-optical aberration and dithering of streamwise structures in supersonic mixing layers were quantificationally studied with BOS. The aberration field of spanwise structures revealed the ribbon-like aberration structures, which heavily restrict the optical performance of a mixing layer. The quantifications of aero-optical aberration and dithering are very important in studying aero-optical performance of supersonic mixing layer. | ZHAO YuXin , YI ShiHe, TIAN LiFeng, HE Lin & CHENG ZhongYu College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China | 2010 | Science China(Physics,Mechanics & Astronomy)2010，53，1： | 13 |
| 8 | Urban expansion in China and its effect on cultivated land before and after initiating'Reform and Open Policy'显示文摘Urbanization in China has expanded at an unprecedented speed since the declaration of 'Reform and Open Policy'and presented many challenges. Unbalanced regional development, appearance of super megacities and concomitant problems,and conflicts between urbanization and cultivated land protection are three critical problems that Chinese urbanization has to face. To develop new plans for foreseeable future urbanization in China, it is critical to understand the evolving history of cities across China. This study maps urban expansion of 60 typical Chinese cities based on large amount of remote sensing data and the labor-intensive image interpretation method, in order to understand the history of urban expansion from the 1970 s to 2013.Results showed that area of cities expanded 5.23 times compared to their area in the 1970 s. Urban expansion in China accelerated three times(1988–1996, 1999–2006, and 2009–2011) and decelerated three times(1997–1998, 2007–2008, and 2012–2013) over the 40 years. The urban area of South China expanded most significantly 9.42 times, while the urban area in Northeast China expanded only 2.37 times. The disparity among different administrative ranks of cities was even greater than(3.81 times) the differences among different regions. Super megacities have been continuously expanding at a fast rate(8.60-fold), and have not shown obvious signs of slowing down. The proportion of cultivated land among the land sources for urban expansion decreased to a small extent in the 1990 s, but cultivated land continues to be the major land source for urban expansion. Effective future urbanization needs controlling the expansion scale of large cities and reasonably developing medium and small cities, as well as balancing regional development. | ZHANG ZengXiang WEN QingKe LIU Fang ZHAO XiaoLi LIU Bin XU JinYong YI Ling HU ShunGuang WANG Xiao ZUO LiJun LI Na LI MinMin SHI LiFeng ZENG Tian JU HongRun | 2016 | Science China Earth Sciences2016，59，10： | 12 |
| 9 | Multiresolution analysis of density fluctuation in supersonic mixing layer显示文摘Due to the difficulties in measuring supersonic density field, the multiresolution analysis of supersonic mixing layer based on experimental images is still a formidable challenge. By utilizing the recently developed nanoparticle based planar laser scattering method, the density field of a supersonic mixing layer was measured at high spatiotemporal resolution. According to the dynamic behavior of coherent structures, the multiresolution characteristics of density fluctuation signals and density field images were studied based on Taylor’s hypothesis of space-time conversion and wavelet analysis. The wavelet coefficients reflect the characteristics of density fluctuation signals at different scales, and the detailed coefficients reflect the differences of approximation at adjacent levels. The density fluctuation signals of supersonic mixing layer differ from the periodic sine signal and exhibit similarity to the fractal Koch signal. The similarity at different scales reveals the fractal characteristic of mixing layer flowfield. The two-dimensional wavelet decomposition and reconstruction of density field images extract the approximate and detailed signals at different scales, which effectively resolve the characteristic structures of the flowfield at different scales. | ZHAO YuXin1, YI ShiHe, TIAN LiFeng, HE Lin & CHENG ZhongYu College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China | 2010 | Science China(Technological Sciences)2010，53，2： | 11 |
| 10 | A flow control study of a supersonic mixing layer via NPLS显示文摘The flow control of a supersonic mixing layer was studied in a supersonic mixing layer wind tunnel with convective Mach number (Mc) at 0.5. The passive control of the mixing layer was achieved by perturbation tapes on the trailing edge of the splitter plate. The control effects of 2D and 3D perturbation tapes with different sizes were compared. The mixing layer was visualized via NPLS,and the transient fine structures were identifiable in NPLS images,which were used to analyze the effects of flow control. The results show that the 2D tapes can enhance the 2D characteristic of the mixing layer,delaying mixing layer transition; and the 3D tapes can enhance the 3D characteristic of the mixing layer,advancing mixing layer transition. 3D structures of the mixing layer were visualized,and the H-type Λ vortexes were found with 3D tapes control. | YI ShiHe HE Lin ZHAO YuXin TIAN LiFeng CHENG ZhongYu | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，12： | 10 |
| 11 | Aero-optical wavefront measurement technique based on BOS and its applications显示文摘A collimated light beam will be refracted if it propagates through a flow-field with index-of-refraction variations,and its wavefront will be distorted.If we measure the deflection angle of the light beam,the gradient of the wavefront can be obtained using the Malus law,and the wavefront aberration can be computed with a reconstruction algorithm.Two characteristics of background oriented schlieren(BOS) are conducive to wavefront aberration measurement:BOS can be used to measure the deflection angle of a light beam by measuring the displacement field between the reference image and the experiment image.Moreover,in a BOS system of Schlieren mode,only the ray perpendicular to the background image can be captured with a camera.This is helpful to measure wavefront aberrations that occur after a planar wavefront has passed through the flow-field.Based on these characteristics of BOS of Schlieren mode,a new wavefront measurement technique,which is called the BOS-based wavefront technique(BOS-WT),is proposed in this paper.It works by constructing the relationship between the displacement of the background image and the aero-optical wavefront gradient and uses the Southwell wavefront reconstruction algorithm.A BOS-WT system was assembled,and its temporal resolution was found to be 6 ns,and its temporal-correlation resolution reached 0.2 μs.A BOS-WT can measure the time-correlation transient wavefront quantitatively.It is simple and easy to operate.In this paper,we also present a study of the aero-optical performance of supersonic mixing layer based on our BOS-WT transient wavefronts at an interval of 5 μs.The results showed the wavefront was transient and distorted after it had passed through the mixing layer.Through the analysis of the data at the 5 μs interval,the temporal evolution of wavefront can be obtained. | TIAN LiFeng YI ShiHe ZHAO YuXin HE Lin CHEN Zhi | 2011 | Chinese Science Bulletin2011，56，22： | 10 |
| 12 | Density field measurement and approximate reconstruction of supersonic mixing layer显示文摘The density field measurement of supersonic mixing layer based on the nanoparticle-based planar laser scattering method was studied.The calibration of experimental images was analyzed,and the relation between tracer particles concentration and local density of flowfield was calibrated with oblique shockwave experiment.According to the characteristic of mixing layer images,the influence of uneven light intensity distribution was calibrated.With these calibration methods,the density field of supersonic mixing layer with convective Mach number at 0.12 was measured.By analyzing the spanwise vortical structures and streamwise density field,the three dimensional(3D) density field was approximately reconstructed,which apparently reflected the 3D structure of supersonic mixing layer. | ZHAO YuXin YI ShiHe TIAN LiFeng HE Lin CHENG ZhongYu | 2010 | Chinese Science Bulletin2010，55，19： | 7 |
| 13 | Experimental study of a supersonic turbulent boundary layer using PIV显示文摘Particle image velocimetry was applied to the study of the statistical properties and the coherent structures of a flat plate turbulent boundary layer at Mach 3. The nanoparticles with a good flow-following capability in supersonic flows were adopted as the tracer particles in the present experiments. The results show that the Van Driest transformed mean velocity profile satisfies the incompressible scalings and reveals a log-law region that extends to y/ =0.4, which is further away from the wall than that in incompressible boundary layers. The Reynolds stress profiles exhibit a plateau-like region in the log-law region. The hairpin vortices in the streamwise-wall-normal plane are identified using different velocity decompositions, which are similar to the results of the flow visualization via NPLS technique. And multiple hairpin vortices are found moving at nearly the same velocity in different regions of the boundary layer. In the streamwise-spanwise plane, elongated streaky structures are observed in the log-law region, and disappear in the outer region of the boundary layer, which is contrary to the flow visualization results. | HE Lin YI ShiHe ZHAO YuXin TIAN LiFeng CHEN Zhi | 2011 | Science China(Physics,Mechanics & Astronomy)2011，54，9： | 6 |
| 14 | An experimental study on fine structures of supersonic laminar/turbulent flow over a backward-facing step based on NPLS显示文摘Fine structures of supersonic flow over a 5 mm high backward facing step(BFS),including expansion wave fan,reattachment shock,supersonic boundary layer were measured in a Ma=3.0 low-noise indraft wind tunnel.By varying the superficial roughness of the wall upstream from the step,supersonic laminar flow and supersonic turbulent flow could be formed over a BFS.Measurements on the spatiotemporal features of the holistic flow field and the fine structures in four typical regions were carried out using NPLS(nano-based planar laser scattering).Flow structures,including expansion wave fan,reattachment shock,supersonic boundary layer and its separation,reattachment and redevelopment are revealed by measuring the holistic structure of the transient flow field.Comparing the two time-averaged flow fields with each other,it is apparent that supersonic turbulent flow over a BFS(STF-BFS) has a larger expansion angle and a shorter recirculation region,and its redeveloped boundary layer increases at a smaller obliquity while the angle of reattachment shock is the same for the supersonic laminar flow over a BFS(SLF-BFS).With regard to time-evolution features,the K-H vortices in the SLF-BFS suffers from shearing,expansion,reattachment and three-dimensional effects while in the STF-BFS large-scale structures are affected by the incline and distortion at the reattachment point due to expansion,viscosity and reverse-pressure.Studies on local regions indicate that in the SLF-BFS,the emergence of compression waves which distinctly converge into a reattachment shock is due to the local convective Mach number and the inducement of K-H vortices in the free shear layer.Nevertheless,in the STF-BFS,compression waves and K-H vortices are barely evident,and the formation of a reattachment shock is related to the wall compressive effect. | CHEN Zhi YI ShiHe HE Lin TIAN LiFeng ZHU YangZhu | 2012 | Chinese Science Bulletin2012，57，6： | 4 |
| 15 | The electromechanical features of LiNbO_(3) crystal for potential high temperature piezoelectric applications显示文摘Lithium niobate(LiNbO_(3),LN)crystal is a multi-functional material with favorable piezoelectric,nonlinear optical and electro-optic properties.In this study,the electromechanical properties of the radial extensional(RE)and the thickness extensional(TE)modes of the congruent LN are studied and the temperature dependent behaviors are revealed.The RE mode electromechanical coupling factors(kp)for the Y-and Z-oriented discs are calculated and found to be 3.8%and 24.7%,respectively,which are nearly the same as the experimental results of 3.8%and 25.2%,respectively.The maximum RE and thickness shear(TS)modes electromechanical coupling factors are obtained to be 47.6%and 68.5%for the Yx/25and Yx/167crystal cuts,respectively.The LN crystal possesses good temperature stability of the electromechanical coupling factors(RE and TE modes)from 20℃ to 500℃,where the variations of kp and kt for the Y-oriented discs are<8.0%and<1.8%,respectively. | Feifei Chen Lingfeng Kong Wei Song Chao Jiang Shiwei Tian Fapeng Yu Lifeng Qin Xian Zhao | 2019 | Journal of Materiomics2019，5，1： | 3 |
| 16 | Experimental and numerical study on instability structure of the supersonic mixing layer(M_c = 0.5)显示文摘The parameters of instability wave of supersonic mixing layer(Mc=0.5,M1=3.5/M2=1.4) are measured by flow visualization and calculated by means of two-dimensional direct numerical simulaitons of the compressible Navier-Stokes equations.In both cases of the mixing layer with harmonic disturbance or not,the comparative results indicate that the wavelength of the two-dimensional wave is equal to the vortex spacing in the streamwise direction because the difference between them is less than 1%.However,the measured convective velocity of the large-scale structure deviates from the theoretical isentropic prediction about 10%.Here the measured value confirms that Mc,2 | YANG WuBing ZHUANG FengGan SHEN Qing GUAN FaMing WANG Qiang YI ShiHe ZHAO YuXin HE Lin TIAN LiFeng | 2009 | Science China(Physics,Mechanics & Astronomy)2009，52，10： | 2 |
| 17 | Study on electrochemical oxidation of 4-chlorophenol on a vitreous carbon electrode using cyclic voltammetry显示文摘 | Xiaoyue Duan Lifeng Tian Wei Liu Limin Chang | 2013 | Electrochimica Acta2013，，： | 1 |
| 18 | Bi-channel near-and far-field optical vortex generator based on a single plasmonic metasurface显示文摘With the recent development of the metasurface,generating an optical vortex in optical far or near fields is realized in various ways.However,to generate vortices in both the near and far fields simultaneously is still a challenge,although it has great potential in the future compact and versatile photonic system.Here,a bi-channel optical vortex generator in both the near and far fields is proposed and demonstrated within a single metasurface,where the surface plasmon vortex and the far-field optical vortex can be simultancously generated under circularly polarized light.The ability of generating vortices with arbitrary topological charges is experimentally demon-strated,which agrces well with simulations.This approach provides great freedom to integrate different vortex generators in a single device and ofers new opprtunities for integrated optical communications,trapping,and other related fields. | QIAO JIANG YANJUN BAO JING LI LIFENG TIAN ToNG CUI LIN SUN BOWEN DU BOWEN LI BENFENG BAI JIA WANG HONGBO SUN Bo SHEN HAN ZHANG FENG LIN XING ZHU ZHEYU FANG | 2020 | Photonics Research2020，8，6： | 1 |
| 19 | Forimation of dicalcium phosphate on magnesium alloy by micro-arc oxidation coupled with hydrothermal treatment 显示文摘 | Limin Chang Lifeng Tian Wei Liu | 2013 | Corrosion Science2013，72，： | 1 |
| 20 | Self-assembled biodegradable micellar nanoparticles o{ am- phiphilic and cationic block copolymer for siRNA delivery 显示文摘 | TIAN MENG SUN JINZHI DU LIFENG YAN | 2008 | Biomaterials2008，29，32： | 1 |
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