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Strain tunability of dielectric and ferroelectric properties in epitaxial lead titanate thin films

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Theoretical & Applied Mechanics Letters 2011年第1期1卷 14-17页

作者： Jie Wang~(a)) School of aeronautics & astronautics,zhejiang university,hangzhou 31002.,china School of aeronautics & astronautics Zhejiang University Hangzhou 310027 China

Many distinguished properties of epitaxial ferroelectric thin films can be tunable through the misfit *** strain tunability of ferroelectric and dielectric properties in epitaxial lead titanate ultrathin films is numerically investigated by using a phase field model,in which the surface effect of polarization is taken into *** response of polarization to the applied electric field in the thickness direction is examined with different misfit strains at room *** is found that a compressive misfit strain increases the coercive field and the remanent polarization while a tensile misfit strain decreases both of *** nonlinear dielectric constants of the thin films with tensile misfit strains are much larger than those of the thin films without misfit strains,which are attributed to the existence of the a/c/a/c multiple domains in the thin films under tensile misfit strains.

关键词： misfit strain ferroelectric thin film dielectric constant phase field model domain structures

Numerical investigation of the effect of sub-grid scale eddies on the dispersed particles by LES/FDF model

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Science china(Technological Sciences) 2010年第5期53卷 1304-1308页

作者： JIN HanHui1,CHEN SuTao1,CHEN LiHua1 & FAN JianRen2 1 School of aeronautics and astronautics,zhejiang university,hangzhou 31002.,china 2 State Key Lab of Clean Energy Utilization,zhejiang university,hangzhou 31002.,china 1. School of aeronautics and astronautics Zhejiang University Hangzhou 310027 China2. State Key Lab of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

An LES/FDF model was developed by the authors to investigate the SGS effect on the particle motion in the gas-particle two-phase plane wake *** simulation results of dispersion rate for different particles were compared with the results without using the FDF *** was shown that the large eddy structure is the dominant factor influencing the particle diffu-sion in space for small particles(small Stokes-number particles),but for intermediate or large diameter particles,the influence of the sub-grid scale eddies on the dispersion rate is in the same order as that of the large *** sub-grid scale eddies increase the particle dispersion rate in most time,but sometimes they decrease the dispersion *** sub-grid scale particle dispersion rate is decided not only by the intensity of sub-grid scale eddies and the Stokes number of the particles,but also by the large eddy structure of the flow *** the particles in isotropic turbulence,the dispersion rate decreases as the particle diameter increases.

关键词： multiphase flow large eddy simulation filtered density function turbulence sub-grid

MARCHING CUBES BASED FRONT TRACKING METHOD AND ITS APPLICATION TO SOME INTERFACE INSTABILITY PROBLEMS

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Journal of Hydrodynamics 2011年第5期23卷 580-588页

作者： WANG Jing-yi ZOU Jian-feng ZHENG Yao REN An-lu 不详 Department of Engineering Mechanics School of Aeronautics and Astronautics Zhejiang University Hangzhou 310027 China

A front tracking method based on a marching cubes isosurface extractor, which is related filter generating isosurfaces from a structured point set, is provided to achieve sharp resolution for the simulation of non-diffusive interfacial flow. Compared with the traditional topology processing procedure, the current front tracking method is easier to be implemented and presents high performance in terms of computational resources. The numerical tests for 2-D highly-shearing flows and 3-D bubbles merging process are conducted to numerically examine the performance of the current methodology for tracking interfaces between two immiscible fluids The Rayleigh-Taylor （RT） and Richtmyer-Meshkov （RM） instability problems are successfully investigated with the present marching cubes based front tracking method.

关键词： interracial flow front tracking marching cubes bubbles merging process Rayleigh-Taylor (RT) instability Richtmyer- Meshkov (RM) instability

An oblivious fragile watermarking scheme for images utilizing edge transitions in BTC bitmaps

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Science china(Information Sciences) 2012年第11期55卷 2570-2581页

作者： ZHANG Yong1,LU ZheMing2 & ZHAO DongNing1 1ATR National Defense Technology Key Laboratory,College of Information Engineering,Shenzhen university,Shenzhen 518060,china 2.chool of aeronautics and astronautics,zhejiang university,hangzhou 31002.,china 1. ATR National Defense Technology Key Laboratory College of Information Engineering Shenzhen University Shenzhen 518060 China2. School of Aeronautics and Astronautics Zhejiang University Hangzhou 310027 China

As one of the famous block-based image coding schemes,block truncation coding(BTC) has been also applied in digital *** BTC-based watermarking or hiding schemes usually embed secret data by modifying the BTC encoding stage or BTC-compressed data,obtaining the watermarked image with poorer quality than the BTC-compressed *** paper presents a new oblivious image watermarking scheme by exploiting BTC *** the traditional schemes,our approach does not really perform the BTC compression on images during the embedding process but utilizes the parity of the number of horizontal edge transitions in each BTC bitmap to guide the watermark embedding and extraction *** embedding process starts by partitioning the original cover image into non-overlapping 4×4 blocks and performing BTC on each block to obtain its BTC *** watermark bit is embedded in each block by modifying at most three pixel values in the block to make sure that the parity of the number of horizontal edge transitions in the bitmap of the modified block is equal to the embedded watermark *** the extraction stage,the suspicious image is first partitioned into non-overlapping 4×4 blocks and BTC is performed on each block to obtain its ***,by checking the parity of the number of horizontal edge transitions in the bitmap,we can extract one watermark bit in each *** results demonstrate that the proposed watermarking scheme is fragile to various image processing operations while keeping the transparency very well.

关键词： fragile image watermarking oblivious watermarking block truncation coding data hiding image authentication

MULTI-MODE OF VORTEX-INDUCED VIBRATION OF A FLEXIBLE CIRCULAR CYLINDER

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Journal of Hydrodynamics 2011年第4期23卷 483-490页

作者： XIE Fang-fang DENG Jian ZHENG Yao School of aeronautics and astronautics Zhejiang University Hangzhou 310027 China

The vortex-induced vibration of a flexible circular cylinder is investigated at a constant Reynolds number of 1000. The finite-volume method on moving meshes is applied for the fluid flow, and the Euler-Bernoulli beam theory is used to model the dynamic response of a flexible cylinder. The relationship between the reduced velocity and the amplitude response agrees well with the experimental results. Moreover, five different vibrating modes appear in the simulation. From the comparisons of their vortex structures, the strength of the wake flow is related to the exciting vibrating mode and different vortex patterns arise for different vibrating modes. Only 2P pattern appears in the first vibrating mode while 2S-2P patterns occur in the other vibrating modes if monitoring at different sections along the length of the cylinder. The vibration of the flexible cylinder can also greatly alter the three-dimensionality in the wake, which needs further studies in our future work, especially in the transition region for the Reynolds number from 170 to 300.

关键词： multi-mode Vortex-Induced Vibration (VIV) three-dimensional instability flexible cylinders Euler-Bemoulli beam

移动容迟网络中基于改进随机路点模型的移动连接路由

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吉林大学学报（工学版） 2011年第S1期41卷 297-303页

作者：李晖浙江大学航空航天学院杭州310027

在移动容迟网络中,考虑到稀疏网络节点混存长时间被无效消息占用情况,将移动连接路由算法与倒数计时器和快速缓存释放策略相结合,提出了加速缓存释放的移动连接路由算法,并研究了节点移动速率、通信距离、节点数量、消息有效时间、场景... 详细信息

在移动容迟网络中,考虑到稀疏网络节点混存长时间被无效消息占用情况,将移动连接路由算法与倒数计时器和快速缓存释放策略相结合,提出了加速缓存释放的移动连接路由算法,并研究了节点移动速率、通信距离、节点数量、消息有效时间、场景尺寸等对算法性能的影响。结果表明:该路由算法在保证传输可靠性的前提下能够提高网络的传输效率。

关键词：通信技术移动延迟网络随机路点模型路由缓存释放

Study on the Burn-resistant Properties of Titanium Alloy Ti6Al4V Surface by Diffusing Copper

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稀有金属材料与工程 2011年第S3期40卷 286-289页

作者： Zhang Gaohui1, Zhang Pingze2, Huang Guoqing1, Peng Xu1, Zheng Shunqi3 1 china Jiliang university, hangzhou 310018, china 2 Nanjing university of aeronautics and astronautics, Nanjing 210016, china 3 Ningbo Branch of china Academy of Ordnance Science, Ningbo 315103, china china Jiliang Univ Hangzhou 310018 Zhejiang Peoples R China Nanjing Univ Aeronaut & Astronaut Nanjing 210016 Peoples R China china Acad Ordnance Sci Ningbo Branch Ningbo 315103 Peoples R China

Copper was diffused on the surface of titanium alloy Ti6Al4V by ion implantation, magnetron sputtering and double glow discharge plasma surface alloying technology respectively to form an alloy layer on the surface of titanium alloy in order to improve the burn-resistance performance of titanium alloy. The result of X-Ray Diffraction shows that the phase of CuTi2 which can improve the burn-resistance performance can be found on the surface of the samples treated by the above three methods. And femtosecond laser ablation experiments show that the burn-resistance property of the titanium alloy can be enhanced by ion implantation, but the alloyed layer is too thin to be applied in practice; both of alloy layer and film can be formed on the surface of titanium alloy by magnetron sputtering, the alloy layer takes evident effect on the burn-resistance properties of titanium alloy while the film has no effect on the burn-resistant properties; alloy layer with Cu can be found on the surface of titanium alloy by the double glow plasma surface alloying technology with the source of pure copper, and its effect on burn-resistance properties of the titanium alloy is evident as the scar area by the laser burning experiment has been reduced heavily.

关键词： titanium alloy burn-resistance ablation

A preliminary study of variations of the Changjiang Diluted Water between August of 1999 and 2006

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Acta Oceanologica Sinica 2009年第6期28卷 1-11页

作者： ZHOU Feng XUAN Jiliang NI Xiaobo HUANG Daji Department of Fluid Mechanics School of Aeronautics and Astronautics of ZhejiangUniversity Hangzhou310027 China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute ofOceanography State Oceanic Administration Hangzhou 310012 China

A large area hypoxia has been already reported respectively by two interdisciplinary surveys off the Changjiang Estuary since summer of 1999 and 2006. The bypoxic zone shows distinct year-to-year variations. Observed oceanographic data are first analysized and reveal a big difference for the Changjiang Diluted Water （CDW） between these two periods. These great changes are related to the tremendous reduction of the freshwater discharge and variations of wind fields between these two years. It is also found that the monthly mean intrusion of Kuroshio and its branches has increased in the northern East china Sea （ECS）, but decreased in the southern ECS in August of 2006 as compared with 1999 on the base of general circulation models. Then, the Regional Ocean Modelling Systems is applied to the East china Sea to evaluate the contributions and relative importance of impacts from the river discharge, wind forcing and open boundary data. Our simulations reproduce the phenomena that more fresh water extends northeastward in 2006 and forms a negative SSS anomaly to the northeast of the river mouth as compared with 1999, which is consistent with observations. The five group numerical tests suggest that the wind forcing dominates the CDW variations followed by the Kuroshio and its branches. The study implies important roles played by hydrodynamic processes on the variability of hypoxic zone in the study areas.

关键词： Changjiang Diluted Water variations dynamics hypoxia

Information Technology and Paradigm Shifting in Organizational Structure and Strategy

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Journal of Systems Engineering and Electronics 1994年第4期5卷 40-49页

作者： WU Xiaobozhejiang university, hangzhou 31002., P. R. china HU XiangpeiHarbin Institute of Technology, Harbin 150001, P.R.chinaDONG ZhiqiangBeijing university of aeronautics & astronautics, Beijing 10083, P.R. china zhejiang university Hangzhou 310027 P. R. China Harbin Institute of Technology Harbin 150001 P.R. China Beijing university of aeronautics & astronautics Beijing 10083 P.R. China

This paper examines the impacts of information technology (IT) on LDCs' competitive conditions, especially the impacts on intra-organization's linkage and technology capability formation via innovation, as the rising ... 详细信息

关键词： Information technology Paradigm Innovation Organizational structure.