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The vibroacoustic response and sound absorption performance of multilayer, microperforated rib-stiffened plates

Acta Mechanica Sinica 2017年第5期33卷 926-941页

作者： Haian Zhou Xiaoming Wang Huayong wu Jianbing Meng School of Mechanical Engineering Shandong University of Technology School of Mechanical Engineering Dalian University of Technology School of Aeronautics Shandong Jiaotong University

The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters-for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing-on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.

关键词： Sound absorption Multilayer Microperforated Rib-stiffened Flexural Vibration

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Bifurcation of thermocapillary convection in a shallow annular pool of silicon melt

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Acta Mechanica Sinica 2007年第1期23卷 43-48页

作者： Yourong Li Lan Peng Shuangying wu Nobuyuki Imaishi College of Power Engineering Chongqing University Chongqing 400044 China Institute for Materials Chemistry and Engineering Kyushu University Fukuoka 816-8580 Japan

In order to understand the nature of surface patterns on silicon melts in industrial Czochralski furnaces, we conducted a series of unsteady threedimensional numerical simulations of thermocapillary convections in thin silicon melt pools in an annular container. The pool is heated from the outer cylindrical wall and cooled at the inner wall. Bottom and top surfaces are adiabatic. The results show that the flow is steady and axisymmetric at small temperature difference in the radial direction. When the temperature difference exceeds a certain threshold value, hydrothermal waves appear and bifurcation occurs. In this case, the flow is unsteady and there are two possible groups of hydrothermal waves with different number of waves, which are characterized by spoke patterns traveling in the clockwise and counter-clockwise directions. Details of the flow and temperature disturbances are discussed and number of waves and traveling velocity of the hydro- thermal wave are determined.

关键词： Computer simulation Thermocapillary convection Semiconducting silicon Bifurcation

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Review of shock wave detection method in CFD post-processing

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Chinese Journal of Aeronautics 2013年第3期26卷 501-513页

作者： wu Ziniu Xu Yizhe Wang Wenbin Hu Ruifeng School of Aerospace Tsinghua University

In the present computational fluid dynamics （CFD） community, post-processing is regarded as a procedure to view parameter distribution, detect characteristic structure and reveal physical mechanism of fluid flow based on computational or experimental results. Field plots by contours, iso-surfaces, streamlines, vectors and others are traditional post-processing techniques. While the shock wave, as one important and critical flow structure in many aerodynamic problems, can hardly be detected or distinguished in a direct way using these traditional methods, due to possible confusions with other similar discontinuous flow structures like slip line, contact discontinuity, etc. Therefore, method for automatic detection of shock wave in post-processing is of great importance for both academic research and engineering applications. In this paper, the current status of methodologies developed for shock wave detection and implementations in post-processing platform are reviewed, as well as discussions on advantages and limitations of the existing methods and proposals for further studies of shock wave detection method. We also develop an advanced post-processing software, with improved shock detection.

关键词： Aerodynamics Automatic detection Computational fluid dynamics Shock wave Post-processing

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Salient object detection via region contrast and graph regularization

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Science China(Information Sciences) 2016年第3期59卷 46-59页

作者： Xingming wu Mengnan DU Weihai CHEN Jianhua WANG School of Automation Science and Electrical Engineering Beihang University

Detection of salient objects in an image is now gaining increasing research interest in computer vision community. In this study, a novel region-contrast based saliency detection solution involving three phases is proposed. First, a color-based super-pixels segmentation approach is used to decompose the image into regions. Second, three high-level saliency measures which could effectively characterize the salient regions are evaluated and integrated in an effective manner to produce the initial saliency map. Finally, we construct a pairwise graphical model to encourage that adjacent image regions with similar features take continuous saliency values, thus producing the more perceptually consistent saliency map. We extensively evaluate the proposed method on three public benchmark datasets, and show it can produce promising results when compared to 14state-of-the-art salient object detection approaches.

关键词： salient object detection region contrast region compactness global distinctness graph regular ization

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System Design and Analysis of Hydrocarbon Scramjet with Regeneration Cooling and Expansion Cycle

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Journal of Thermal Science 2015年第4期24卷 350-355页

作者： wu Xianyu YANG Jun ZHANG Hua SHEN Chibing College of Aerospace Science and Engineering National Univ.of Defense Technology

A new expansion cycle scheme of the scramjet engine system including a hydrocarbon-fuel-based(kerosene)regenerative cooling system and supercritical/cracking kerosene-based turbo-pump was proposed in this *** this cycle scbeme,the supercritical/cracking kerosene with high pressure and high temperature is formed through the cooling *** then,in order to make better use of the high energy of the supercritical/cracking fuel,the supercritical/cracking kerosene fuel was used to drive the turbo-pump to obtain a high pressure of the cold kerosene fuel at the entrance of the cooling *** the end,the supercritical/cracking kerosene from the turbine exit is injected into the scramjet *** supercritical/cracking kerosene fuel can decrease the fuel-air mixing length and increase the combustion efficiency,due to the gas state and low molecular weight of the cracking *** order to ignite the cold kerosene in the start-up stage,the ethylene-assisted ignition subsystem was *** the present paper,operating modes and characteristics of the expansion cycle system are first *** then,the overall design of the system and the characterisitics of the start-up process are analyzed numerically to investigate effects of the system parameters on the scramjet start-up *** results show that the expansion cycle system proposed in this paper can work well under typical *** research work in this paper can help to make a solid foundation for the research on the coupling characteristics between the dynamics and thermodynamics of the scramjet expansion cycle system.

关键词： scramjet supercritical/cracking hydrocarbon regenerative cooling expansion cycle

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Non-buckled vitrectomy for retinal detachment with inferior breaks and proliferative vitreoretinophathy

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International Journal of Ophthalmology(English edition) 2012年第5期5卷 591-595页

作者： Yan Sheng, wu Liu Department of Ophthalmology the First Affiliated Hospital College of Medicine Zhejiang University Hangzhou 310009 Zhejiang Province China Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Science Key Lab Beijing 100730 China

AIM: To investigate the efficacy of non-buckled vitrectomy with classical endotamponade agents in the treatment of primary retinal detachment (RD) complicated by inferior breaks and proliferative vitreoretinophathy (PVR). METHODS: A retrospective, consecutive and case series study of 40 patients with inferior break RD and PVR >= C1 was conducted. All patients underwent a standard 3-port 20-gauge pars plana vitrectomy (PPV) with gas or silicone oil tamponade without supplementary scleral buckling. The vitreous and all proliferative membrane were completely removed, and retinectomy was performed when necessary. The mean follow-up was 12.5 months. The primary and final anatomic success rate, visual acuity and complications were recorded and analyzed. RESULTS: Primary anatomic success rate was achieved in 35 of 40 eyes (87.5%) and the final anatomic success rate was 100%. The most common cause of redetachment was recurrent PVR. The best-corrected visual acuity (BCVA) at final follow-up was improved in 34 eyes (85%), remained stable in 1 eye (2.5%), and worsened in 5 eyes (12.5%). The mean visual acuity at final follow-up was improved significantly (P=0.000). CONCLUSION: This retrospective study provides evidence that vitrectomy without scleral buckling seemed to be an effective treatment for inferior break RD with PVR. With complete removal of vitreous and proliferative membranes and timing of retinectomy, the inferior breaks which complicated with PVR could be dosed successfully without additional sclera! buckling.

关键词： retinal detachment inferior retinal break proliferative vitreoretinophathy vitrectomy

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Analysis of the characteristics of the harmonics coefficient J_2 of the Earth's gravity field in different periods

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Chinese Science Bulletin 2012年第14期57卷 1626-1630页

作者： QU WeiJing wu Bin Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The characteristics of the geopotential coefficient J2 in different periods are analyzed using satellite laser ranging data spanning the last 27 *** satellites used in the analysis are Lageos1 and *** variations in J2 are obtained by determining the dynamic *** results show that there are strong seasonal and long-term *** different data spans,the seasonal variations agree well in terms of both amplitude and *** all the data,the amplitude and phase of the annual term are 2.5 10-10 and 127°,respectively,while the amplitude and phase of the semiannual term are 0.94 10-10 and 213°,*** the case of long-term variation,the secular variation in J2(J2) is-2.2 10-11 a-1 from 1984 to 2010.J2 differs for the different periods because of interannual variations,such as the "1998 anomaly".Another anomaly may have taken place during *** the cause of the anomaly is unknown,it is an important observational constraint on the shape of the Earth.

关键词：地球重力场谐波系数特征卫星激光测距长期变化季节变化年际变化形状约束

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Submarine slide evidence for late Miocene strike-slip reversal of the Red River Fault

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Science China Earth Sciences 2016年第11期59卷 2231-2239页

作者： WANG DaWei wu ShiGuo LI ChunFeng YAO GenShun Institute of Deep-sea Science and Engineering Chinese Academy of Sciences Sanya 572000 China Ocean College Zhejiang University Zhoushan 310013 China PetroChina Hangzhou Institute of Geology Hangzhou 310023 China

During the late Miocene(~5.5 Ma), a large-scale submarine slide with an area of approximately 18000 km^2 and a maximum thickness of 930 m formed in the deep-water region of the Qiongdongnan Basin. The large-scale submarine slide has obvious features in seismic profile, with normal faults in the proximal region, escarpments at the lateral boundary, and a pronounced shear surface at the base. The internal seismic reflections are chaotic and enclosed by parallel and sub-parallel seismic *** main direction of sediment transport was from south to north and the main sediment source was the southern region of the Qiongdongnan Basin, which is located in the east of the Indo-China Peninsula and the north of the Guangle uplift. In this region,late Miocene strike-slip reversal of the Red River Fault, uplift and increased erosion of the Indo-China Peninsula, and an abrupt rise in the rate of deposition in the western part of the South China Sea provided the basic conditions and triggering mechanism for the large-scale submarine slide. The discovery of the large-scale submarine slide provides sedimentological evidence for the tectonic event of late Miocene strike-slip reversal of the Red River Fault. It can also be inferred that the greatest tectonic activity during the process of the Red River Fault reversal occurred at ~5.5 Ma from the age of top surface of the submarine slide.

关键词： Red River Fault Qiongdongnan Basin Deep-water Submarine slide Seismic reflection character

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A Posture Recognition System for Rat Cyborg Automated Navigation

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Chinese Journal of Electronics 2018年第4期27卷 687-693页

作者： ZHANG Zhenchuan YANG Yingchun wu Zhaohui MA Qian College of Computer Science and Technology Zhejiang University College of Computer Science and Technology Qiushi Academy for Advanced Studies Zhejiang University

Rat cyborg is a rat which can receive cerebral commands and act as human wants. The navigation task is a widely used scenario in which the rat cyborg is required to walk along a specified path according to commands. Mostly the commands are given by human operators, but there’s a need for automatic control which is quite challenging since several modules need to be elaborately combined together to work as a whole, among which the monitoring system and the commands model are two major components. Previously, few attempts were made for behavior monitoring of rat cyborg. Existing works often implement an over-simple rat information extractor which is capable of giving only a few parameters of the rat cyborg, which greatly limited the performance of their automatic control accuracy. In response to this requirement,we develop a monitoring system that is capable of giving detailed motion parameters and accurate body postures of the rat cyborg. We explore the possibility of recognizing rat postures using shape information, which is described by the powerful Zernike moments. We propose several simple shape descriptors which are fast to compute and achieve acceptable performance.

关键词： Rat cyborg Posture recognition Rat posture

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Into Africa via docked India: a fossil climbing perch from the Oligocene of Tibet helps solve the anabantid biogeographical puzzle

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Science Bulletin 2019年第7期64卷 455-463页

作者： Feixiang wu Dekui He Gengyu Fang Tao Deng Key Laboratory of Vertebrate Evolution and Human Origins Institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Center for Excellence in Life and Paleoenvironment Chinese Academy of Sciences Key Laboratory of Aquatic Biodiversity and Conservation Institute of Hydrobiology Chinese Academy of Sciences College of Earth Sciences University of Chinese Academy of Sciences

The northward drift of the Indian Plate and its collision with Eurasia have profoundly impacted the evolutionary history of the terrestrial organisms, especially the ones along the Indian Ocean rim. Climbing perches(Anabantidae) are primary freshwater fishes showing a disjunct south Asian-African distribution,but with an elusive paleobiogeographic history due to the lack of fossil evidence. Here, based on an updated time-calibrated anabantiform phylogeny integrating a number of relevant fossils, the divergence between Asian and African climbing perches is estimated to have occurred in the middle Eocene(ca.40 Ma, Ma: million years ago), a time when India had already joined with Eurasia. The key fossil lineage is ?Eoanabas, the oldest anabantid known so far, from the upper Oligocene of the Tibetan *** range reconstructions suggest a Southeast Asian origin in the early Eocene(ca. 48 Ma) and subsequent dispersals to Tibet and then India for this group. Thereby we propose their westbound dispersal to Africa via the biotic bridge between India and Africa. If so, climbing perch precursors had probably followed the paleobiogeographical route of snakehead fishes, which have a slightly older divergence between African and Asian taxa. As such, our study echoes some recent molecular analyses in rejecting the previously held ‘‘Gondwana continental drift vicariance" or late Mesozoic dispersal scenarios for the climbing perches, but provides a unique biogeographical model to highlight the role of the preuplift Tibet and the docked India in shaping the disjunct distribution of some air-breathing freshwater fishes around the Indian Ocean.

关键词： Climbing perches Asian-African disjunct distribution Biogeography Indian subcontinent Tibet

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