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1Hierarchical microstructures with high spatial frequency laser induced periodic surface structures possessing different orientations created by femtosecond laser ablation of silicon in liquids显示文摘High spatial frequency laser induced periodic surface structures(HSFLs)on silicon substrates are often developed on flat surfaces at low fluences near ablation threshold of 0.1 J/cm2,seldom on microstructures or microgrooves at relatively higher fluences above 1 J/cm^2.This work aims to enrich the variety of HSFLs-containing hierarchical microstructures,by femtosecond laser(pulse duration:457 fs,wavelength:1045 nm,and repetition rate:100 kHz)in liquids(water and acetone)at laser fluence of 1.7 J/cm^2.The period of Si-HSFLs in the range of 110–200 nm is independent of the scanning speeds(0.1,0.5,1 and 2 mm/s),line intervals(5,15 and 20μm)of scanning lines and scanning directions(perpendicular or parallel to light polarization direction).It is interestingly found that besides normal HSFLs whose orientations are perpendicular to the direction of light polarization,both clockwise or anticlockwise randomly tilted HSFLs with a maximal deviation angle of 50°as compared to those of normal HSFLSs are found on the microstructures with height gradients.Raman spectra and SEM characterization jointly clarify that surface melting and nanocapillary waves play important roles in the formation of Si-HSFLs.The fact that no HSFLs are produced by laser ablation in air indicates that moderate melting facilitated with ultrafast liquid cooling is beneficial for the formation of HSFLs by LALs.On the basis of our findings and previous reports,a synergistic formation mechanism for HSFLs at high fluence was proposed and discussed,including thermal melting with the concomitance of ultrafast cooling in liquids,transformation of the molten layers into ripples and nanotips by surface plasmon polaritons(SPP)and second-harmonic generation(SHG),and modulation of Si-HSFLs direction by both nanocapillary waves and the localized electric field coming from the excited large Si particles.Dongshi Zhang Koji Sugioka 2019Opto-Electronic Advances2019,2,3:17
2A series solution for surface motion amplification due to underground twin tunnels:incident SV waves显示文摘A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjectcd to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method. The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion. It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed.梁建文 张浩 Vincent W Lee 2003Earthquake Engineering and Engineering Vibration2003,2,2:13
3High-resolution 3D crustal S-wave velocity structure of the MiddleLower Yangtze River Metallogenic Belt and implications for its deep geodynamic setting显示文摘The Middle-Lower Yangtze River Metallogenic Belt(MLYMB) is an important mineral resource region in China.High-resolution crustal models can provide crucial constraints to understand the ore-forming processes and geodynamic setting in this region. Using ambient seismic noise from 107 permanent and 82 portable stations in the MLYMB and the adjacent area,we present a new high-resolution 3D S-wave velocity model of this region. We first extract 5–50 s Rayleigh wave phase velocity dispersion data by calculating ambient noise cross-correlation functions(CFs) and then use the surface wave direct inversion method to invert the mixed path travel times for the 3D S-wave velocity structure. Checkerboard tests show that the horizontal resolution of the 3D S-wave velocity model is approximately 0.5°–1.0° and that the vertical resolution decreases with increasing noise and depth. Our high-resolution 3D S-wave velocity model reveals:(1) AV-shaped high-velocity zone(HVZ) is located in the lower crust and the uppermost mantle in the study region. The western branch of the HVZ passes through the Jianghan Basin,the Qinling-Dabie orogenic belt and the Nanxiang Basin. The eastern branch, which almost completely covers the main body of the MLYMB, is located near the Tanlu Fault. The low-velocity anomalies between the western and eastern branches are located in the area of the Qinling-Dabie orogenic belt.(2) High-velocity uplifts(HVUs) are common in the crust of the MLYMB,especially in the areas near the Tanlu Fault, the Changjiang Fault and the Yangxin-Changzhou Fault. The intensities of the HVUs gradually weaken from west to east. The V-shaped HVZ in the lower crust and uppermost mantle and the HVUs in the middle and lower crust likely represent cooled mantle intrusive rocks. During the Yanshanian period, fault systems formed in the MLYMB due to the convergence between the South China Plate and the North China Plate, the multiple-direction drifting of the PaleoPacific Plate and its subduction beneath the Eurasian Plate. The dehydration of the cold oceanic crust led to partial melting in the upper mantle. Temperature differences caused strong convection of the upper mantle material that underplated the lower crust and rose to near the surface along the deep fault systems. After mixing with the crustal materials, mineralization processes, such as assimilation and fractional crystallization, occurred in the MLYMB.Song LUO Huajian YAO Qiusheng LI Weitao WANG Kesong WAN Yafeng MENG Bin LIU 2019Science China Earth Sciences2019,62,9:13
4An analysis of surface acoustic wave propagation in a plate of functionally graded materials with a layered model显示文摘In a homogeneous plate, Rayleigh waves will have a symmetric and anti-symmetric mode regarding to the mid-plane with different phase velocities. If plate properties vary along the thickness, or the plate is of functionally graded material (FGM), the symmetry of modes and frequency behavior will be modified, thus producing dif-ferent features for engineering applications such as amplifying or reducing the velocity and deformation. This kind of effect can also be easily realized by utilizing a layered structure with desired material properties that can produce these effects in terms of velocity and displacements, since Rayleigh waves in a solid with gen-eral material property grading schemes are difficult to analyze with known methods. Solutions from layered structures with exponential and polynomial property grad-ing schemes are obtained from the layered model and comparisons with known analytical results are made to validate the method and examine possible applica-tions of such structures in engineering.GAO LiMing WANG Ji ZHONG Zheng DU JianKe 2008Science China(Physics,Mechanics & Astronomy)2008,51,2:5
5Fabrication and characterization of one-port surface acoustic wave resonators on semi-insulating GaN substrates显示文摘One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy(HVPE)and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [1120] GaN and [1100] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film(~1%)reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8-μm Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.吉雪 董文秀 张育民 王建峰 徐科 2019Chinese Physics B2019,28,6:5
6Multi-lens stereo reconstruction of wave surface in a wave basin显示文摘A new method is developed to measure the wave surface elevation in a wave basin.A thin film of tiny granules floating on the free surface ensures the formation of the dot grid pattern on the wave surface.The dot grid pattern is generated by a high-brightness projector.The granule film has little influence on the wave propagation in a wave basin.The measuring system is validated by the experiments of the propagation of solitary wave in water of uniform depth.It turns out that the time series of the surface elevation measured by the multi-lens stereo reconstruction method agree well with that measured by wave gauges.The errors of the measuring system are discussed.This work sheds a light on measuring the local wave field with high precision and efficiency in laboratory.Qian Wang Yong-liu Fang Hua Liu 2019Journal of Hydrodynamics2019,31,5:5
7OPTIMIZATION OF A WAVE CANCELLATION MULTIHULL SHIP USING CFD TOOLS显示文摘A simple CFD tool, coupled to a discrete surface representation and a gradient based optimization procedure, is applied to the design of optimal hull forms and optimal arrangement of hulls for a wave cancellation multihull ship. The CFD tool, which is used to estimate the wave drag, is based on the zeroth order slender ship approximation. The hu ll surface is represented by a triangulation, and almost every grid point on the surface can be used as a design variable. A smooth surface is obtained via a si mplified pseudo shell problem. The optimal design process consists of two steps . The optimal center and outer hull forms are determined independently in the fi rst step, where each hull forms are determined independently in the first step, where each hull keeps the same displacement as the original design while the wav e drag is minimized. The optimal outer hull arrangement is determined in the se cond step for the optimal center and outer hull forms obtained in the first step . Results indicate that the new design can achieve a large wave drag reduction i n comparison to the original design configuration.C. Yang, R. L■hner, O. Soto (School of Computational Sciences, George Mason University Fairfax VA 22030-4444, USA) 2002Journal of Hydrodynamics2002,14,1:5
8Imaging shallow structure with active-source surface wave signal recorded by distributed acoustic sensing arrays显示文摘Distributed acoustic sensing(DAS) is one recently developed seismic acquisition technique that is based on fiber-optic sensing. DAS provides dense spatial spacing that is useful to image shallow structure with surface waves.To test the feasibility of DAS in shallow structure imaging,the PoroTomo team conducted a DAS experiment with the vibroseis truck T-Rex in Brady's Hot Springs, Nevada, USA.The Rayleigh waves excited by the vertical mode of the vibroseis truck were analyzed with the Multichannel Analysis of Surface Waves(MASW) method. Phase velocities between5 and 20 Hz were successfully extracted for one segment of cable and were employed to build a shear-wave velocity model for the top 50 meters. The dispersion curves obtained with DAS agree well with the ones extracted from co-located geophones data and from the passive source Noise Correlation Functions(NCF). Comparing to the co-located geophone array, the higher sensor density that DAS arrays provides help reducing aliasing in dispersion analysis, and separating different surface wave modes. This study demonstrates the feasibility and advantage of DAS in imaging shallow structure with surface waves.Zhenghong Song Xiangfang Zeng Clifford H.Thurber Hebert F.Wang Dante Fratta 2018Earthquake Science2018,31,4:4
9Surface acoustic wave humidity sensors based on uniform and thickness controllable graphene oxide thin films formed by surface tension显示文摘Graphene oxide(GO)is a promising candidate for humidity sensing,and the uniformity and thickness of GO films are important for the reproducibility and test signal strength of humidity sensors.In this paper,uniform and thicknesscontrollable GO films are first formed by the surface tension of different concentrations of GO solution and then transferred to surface acoustic wave(SAW)humidity sensors.This GO film formation and transfer process has very good repeatability and stability,as evidenced by the humidity response of the sensors.With the help of the uniform and highly oxidized GO film,the humidity sensors show a significantly high sensitivity(absolute sensitivity of 25.3 kHz/%RH and relative sensitivity of 111.7 p.p.m./%RH)in a wide test range from 10%RH to 90%RH with very little hysteresis(<1%RH).The sensors achieve good reversibility,excellent short-term repeatability and stability.Moreover,the humidity sensors also show a fast response and recovery time of<10 s.Xianhao Le Yihan Liu Li Peng Jintao Pang Zhen Xu Chao Gao Jin Xie 2019Microsystems & Nanoengineering2019,5,1:4
10响应面法优化棉籽油超声强化合成生物柴油工艺的研究显示文摘以棉籽油为原料,KOH为催化剂,通过超声波强化制备生物柴油(FAME)。采用四因素二次正交旋转组合设计实验。结果表明:采用超声波强化与机械搅拌反应体系相比,反应时间从40min缩短至20min,节能效果明显;得出了超声强化合成FAME的最佳工艺条件为:醇油比6.5:1,超声时间20min,占空比28%,催化剂用量0.9%,FAME的得率为97.35%,所得生物柴油各项指标基本达到欧洲EN14214和0#生物柴油标准。王璐 徐小琳 韩军 吴玉龙 李春 2010太阳能学报2010,31,6:4
11A series solution for surface motion amplification due to underground group cavities:Incident P waves显示文摘A series solution for surface motion amplification due to underground group cavities for incident plane P waves isderived by Fourier-Bessel series expansion method. It is shown that underground group cavities significantly am-plify the surface ground motion nearby. It is suggested that the effect of subways on ground motion should be con-sidered when the subways are planned and designed.LIANG Jian-wen(梁建文) ZHANG Hao(张浩) Vincent W Lee 2004Acta Seismologica Sinica(English Edition)2004,17,3:3
12Smooth constraint inversion technique in genetic algorithms and its application to surface wave study in the Tibetan Plateau显示文摘吴建平 明跃红 曾融生 2001Acta Seismologica Sinica(English Edition)2001,14,1:3
13On the role of topographic ampli fi cation in seismic slope instabilities显示文摘Surface wave generation due to body wave propagation near ground surface has been discussed in the literature.This phenomenon,typically occurring in topographic changing areas,along with its interaction with body waves(SV),decreases precision of formulas for evaluation of slope displacement.This signi fi cant fact caused the researchers not only to investigate the combined surface and SV waves motion pattern,but also to consider its effect on structures built on the slopes.In order to reveal the phenomenon,several fi nite element numerical studies have been performed by ABAQUS programme.Besides,two physical model slopes simulating the landslide occurrence have been constructed and tested by shaking table device.The results of induced and calculated accelerations obtained by two approaches have been compared and Rayleigh wave generation has been proved.Furthermore,the slope displacements have been calculated by various empirical methods and the results were compared with numerical ones.The results proved that in order to increase the precision of empirical formulas for displacement prediction,surface wave effect should be taken into account.Finally,a concept of'effective depth of sur fi cial ampli fi cation'is introduced and its effect on dynamic slope stability is analysed.Fardin Jafarzadeh Mohammad Mahdi Shahrabi Hadi Farahi Jahromi 2015Journal of Rock Mechanics and Geotechnical Engineering2015,7,2:3
14Acoustic wave detection of laser shock peening显示文摘Jiajun Wu Jibin Zhao Hongchao Qiao Xuejun Liu Yinuo Zhang Taiyou Hu 2018Opto-Electronic Advances2018,1,9:3
15Low regularity well-posedness for the viscous surface wave equation显示文摘In this paper, we prove the local well-posedness of the viscous surface wave equation in low regularity Sobolev spaces. The key points are to establish several new Stokes estimates depending only on the optimal boundary regularity and to construct a new iteration scheme on a known moving domain. Our method could be applied to some other fluid models with free boundaries.Xiaoxia Ren Zhaoyin Xiang Zhifei Zhang 2019Science China Mathematics2019,62,10:2
16The hydrothermal wave of large-Prandtl-number fluid in a shallow cavity显示文摘The hydrothermal wave was investigated numerically for large-Prandtl-number fluid (Pr = 105.6) in a shallow cavity with different heated sidewalls. The traveling wave appears and propagates in the direction opposite to the surface flow (upstream) in the case of zero gravity when the applied temperature difference grows and over the critical value. The phase relationships of the disturbed velocity,temperature and pressure demonstrate that the traveling wave is driven by the disturbed tem-perature,which is named hydrothermal wave. The hydrothermal wave is so weak that the oscillatory flow field and temperature distribution can hardly be observed in the liquid layer. The exciting mechanism of hydrothermal wave is analyzed and discussed in the present paper.TANG ZeMei & HU WenRui National Microgravity Laboratory,Institute of Mechanics,Chinese Academy of Sciences,Beijing 100080,China 2007Science China(Physics,Mechanics & Astronomy)2007,50,6:2
17Effects of surface drag on low-level frontogenesis within baroclinic waves显示文摘Using a three-dimensional nonhydrostatic mesoscale numerical model (MM5), the evolution and structures of baroclinic waves with and without surface drag in case of dry and moist atmosphere are simulated, with special emphases on the effects of surface drag on the low-level frontal structure and frontogenesis. There are two different effects of surface drag on the low-level frontogenesis in the dry case. On one hand, the surface drag weakens the low-level frontogenesis and less inclined to develop the baroclinic wave due to the dissipation. But on the other hand, the surface drag induces a strong ageostrophic flow, which prolongs the low-level frontogenesis and finally leads to the enhancement of cold front. Compared with the no surface drag case, the surface drag increases the frontal slope espe- cially in the boundary layer, where the front is almost vertical to the surface, and then enhances the prefrontal vertical motion. All these conclusions expanded the analytical theory of Tan and Wu (1990). In the moist atmosphere, the influence of surface drag on frontal rainbands is also obvious. The surface drag weakens the convection, and reduces the energy dissipation near the surface when the initial relative humidity is relatively weak. At this time, the confluence induced post-frontal updrafts moves across the cold front and reinforces the prefrontal convection, which is beneficial to the maintenance of the rainband in cold sector. Given the enhancement of relative humidity, the moist convection domi- nates the low-level frontogenesis while the retardation of surface drag on energy dissipation is not obvious, therefore the effects of surface drag on the low-level frontogenesis and precipitation are re- duced.ZHANG Yi TAN ZheMin 2007Science China Earth Sciences2007,50,2:2
18SOURCE RADIATION AND RESPONSES OF WAVE PROPAGATION显示文摘Recordings of seismic waves propagating from earthquake source to a station at the earth’s surface are a system response function. The convolution operator in time domain can be simplified as a multiplication operator in frequency domain. We discuss in frequency domain the separation of source, path and site effects for global scaling of earthquake source radiation. Also discussed are source scaling model, faulting mechanism, and the H/V inversion problems with crustal and near surface structures. Gross features of apparent source spectra appear to be not much region dependent although there may be difference between tectonic styles within a region of tectonic mixture for which we need further study as data accumulate. Vertical spectra may be a better approach to approximate source radiation, as it has less crustal amplification effects than horizontal spectra. The H/V ratio is evidently a comprehensive indicator of amplification effects from near surface to deep structure. This gives it potential as an inversion tool to deduce site crustal structure.CHEN Sheng zao 1 and Gail M Atkinson 2 (1. Geomatrix Consultants, Inc., 2101 Webster St., 12 th Floor, Oakland, CA 94612, USA, formerly at Dept. Earth Sciences & Ottawa Carleton Geoscience Center, Carleton University, Ottawa, Canada 2. Dept. Ea 2001Geotectonica et Metallogenia2001,25,1:2
19The 3-D structure of shear wave in South China and the southward extension of Tanlu fault显示文摘By processing the CSND Rayleigh wave data with the matched filter FTAN technique, Rayleigh wave dispersion for southeast China is obtained. The 4°×4°S wave dispersion of the pure path is calculated using random inversion scheme, and 3-D S wave velocity structure is set up. Incorporating the above-mentioned results with wide angle seismic sounding data, we studied structure framework and the extending of faults in this area, which demonstrates that the depth of Moho in South China varies from 30 to 40 km, shallower from west to east. The depth of Moho varies from 25 to 28 km for the offshore. The depth of the asthenosphere in upper mantle varies from 60 to 100 km. The depth difference of layers at the two sides of Tanlu fault is more than 10 km at the south part of the Yangtze River, and the fault extends downward more than 170 km. The fault exceeds the main land at Hainan Island and slips into the southern China Sea. Both Tanlu fault and the huge bend of gravity gradient anomaly are influenced byTENG Jiwen WANG Guangjie ZHANG Zhongjie HU Jiafu 2001Chinese Science Bulletin2001,46,4:2
20Application of Laser Ultrasonic Technique for Non-contact Detection of Angled Surface Defects显示文摘Based on the finite element method,the angled surface defects have been investigated by using the laser generated surface acoustic wave(SAW).The feature of laser generated SAW interaction with the angled defect is analyzed in time and frequency domains.An increase in the amplitude of SAW at the edge of the defect is observed,and the spectral feature is angle dependent.With the angle decreasing from 120°to 30°,the maximum amplitude of frequency spectrum of SAW increases gradually.The corresponding experimental results verify the feasibility of numerical analyses and reach a good agreement with simulation results.Guo Ruipeng Liu Jinghua Wang Haitao 2018Transactions of Nanjing University of Aeronautics and Astronautics2018,35,5:2
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