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New results on global output-feedback stabilization for nonlinear systems with unknown growth rate

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控制理论与应用（英文版） 2013年第3期11卷 401-408页

作者： Xuehua YAN Yungang liu School of Control Science and Engineering Shandong University

In this paper, the global asymptotic stabilization by output feedback is investigated for a class of uncertain nonlinear systems with unmeasured states dependent growth. Compared with the closely related works, the remarkableness of the paper is that either the growth rate is an unknown constant or the dimension of the closed-loop system is significantly reduced, mainly due to the introduction of a distinct dynamic high-gain observer based on a new updating law. Motivated by the related stabilization results, and by skillfully using the methods of universal control and backstepping, we obtain the design scheme to an adaptive output-feedback stabilizing controller to guarantee the global asymptotic stability of the resulting closed-loop system. Additionally, a numerical example is considered to demonstrate the effectiveness of the proposed method.

关键词： Uncertain nonlinear systems Global asymptotic stabilization Adaptive control Output feedback Dynamic high gain

Moments of discounted dividend payments in a risk model with randomized dividend-decision times

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Frontiers of Mathematics in China 2017年第2期12卷 493-513页

作者： Zhimin ZHANG Chaolin liu College of Mathematics and Statistics Chongqing University Chongqing 401331 China

We consider a perturbed compound Poisson risk model with randomized dividend-decision times. Different from the classical barrier dividend strategy, the insurance company makes decision on whether or not paying off dividends at some discrete time points （called dividend-decision times）. Assume that at each dividend-decision time, if the surplus is larger than a barrier b 〉 O, the excess value will be paid off as dividends. Under such a dividend strategy, we study how to compute the moments of the total discounted dividend payments paid off before ruin.

关键词： Moments of discounted dividends compound Poisson model,integro-differential equation ruin

Experimental study on visualization of the flow field in microtube

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Science China(Technological Sciences) 2005年第5期48卷 521-529页

作者： liu Zhigang ZHAO Yaohua Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China

An experimental study was conducted to visualize the flow field and confirm the transitional Reynolds number from laminar to turbulent flow, as distilled water flows through quartz glass microtubes with inner diameter 315 and 520 μm. With gentian violet as colorant, the flow field pictures in the microtube, and therefore, is shot by a CCD camera with a microscope at different Reynolds numbers. Pressure drop data were also used to characterize the friction factor for those microtubes in the Reynolds number range of 200–2300. The experimental results clearly showed that the flow in the microtube was the laminar state and the friction factors agreed well with the Poiseuille equations when the Reynolds number was low. As the Reynolds number was larger than 1200 and 1500 for the microtube with inner diameter 315 and 520 μm, respectively, the friction factor departed from the classical laminar solution due to the earlier transition from laminar to tubulent flow. The flow turned into full turbulent when the Reynolds number reached 1500–1800.

关键词： visual experiment, microtube, microscale flow, friction factor, turbulent transition.

Symplectic Group Actions on Homotopy Elliptic Surfaces

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Chinese Annals of Mathematics,Series B 2014年第6期35卷 873-884页

作者： Yulai WU Ximin liu School of Mathematical Sciences Dalian University of Technology

In this paper, the authors study the homologically trivial symplectic group actions on homotopy elliptic surfaces E(n) and get some rigidity results.

关键词： Symplectic action Homologically trivial g-Signature theorem Fixed-point data

Spatial chaos-based image encryption design

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Science China(Physics,Mechanics & Astronomy) 2009年第2期52卷 177-183页

作者： liu ShuTang SUN FuYan College of Control Science and Engineering Shandong UniversityJi’nan 250061China

In recent years, the chaos based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques, but the drawbacks of small key space and weak security in one-dimensional chaotic cryptosystems are obvious. In this paper, permutation and sub- stitution methods are incorporated to present a stronger image encryption algorithm. Spatial chaotic maps are used to realize the position permutation, and to confuse the relationship between the ci- pher-image and the plain-image. The experimental results demonstrate that the suggested encryption scheme of image has the advantages of large key space and high security; moreover, the distribution of grey values of the encrypted image has a random-like behavior.

关键词： spatial chaos two-dimensional logistic map spatial bifurcation image encryption

Liquid phase 3D printing for quickly manufacturing conductive metal objects with low melting point alloy ink

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Science China(Technological Sciences) 2014年第9期57卷 1721-1728页

作者： WANG Lei liu Jing Beijing Key Laboratory of CryoBiomedical Engineering and Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences Department of Biomedical Engineering School of Medicine Tsinghua University

Conventional 3D metal printings are generally time-consuming as well as lacking of high performance printable *** an alternative way,here we proposed the method of liquid phase 3D printing for quickly making conductive metal *** introducing metal alloys whose melting point is slightly above room temperature as printing inks,several representative structures spanning from one,two and three dimension to more complex patterns were demonstrated to be quickly *** with the air-cooling in a conventional 3D printing,the liquid-phase-manufacturing offers a much higher cooling rate and thus significantly improves the speed in fabricating the target metal *** unique strategy also efficiently prevents the liquid metal inks from air oxidation,which is hard to avoid otherwise in an ordinary 3D *** key physical factors(such as properties of the cooling fluid,air pressure within the syringe barrel and needle diameter,types and properties of the printing ink)and several interesting intermediate fluids interaction phenomena between liquid metal and conventional cooling fluids such as water or ethanol,which evidently affecting the printing quality,were *** addition,a basic route to make future liquid phase 3D printer incorporated with both syringe pump and needle arrays was also *** liquid phase 3D printing,which owns potential values not available in a conventional method,opens an efficient way for quickly making conductive metal objects in the coming time.

关键词： liquid phase 3D printing liquid metal printer rapid prototyping low melting point metal liquid cooling oxidation

Improved smoothed L0 reconstruction algorithm for ISI sparse channel estimation

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The Journal of China Universities of Posts and Telecommunications 2014年第2期21卷 40-47页

作者： liu Ting ZHOU Jie Department of Communications Nanjing University of Information Science and Technology Department of Electronic and Electrical Engineering Niigata University

In this paper, the problem of inter symbol interference （ISI） sparse channel estimation in wireless communication with the application of compressed sensing is investigated. However, smoothed L0 norm algorithm （SL0） has ＇notched effect＇ due to the negative iterative gradient direction. Moreover, the property of continuous function in SL0 is not steep enough, which results in inaccurate estimations and low convergence. Afterwards, we propose the Lagrange multipliers as well as Newton method to optimize SL0 algorithm in order to obtain a more rapid and efficient signal reconstruction algorithm, improved smoothed L0 （ISL0）. ISI channel estimation will have a direct effect on the performance of ISI equalizer at the receiver. So, we design a pre-filter model which with no considerable loss of optimality and do analyses of the equalization methods of the sparse multi-path channel. Real-time simulation results clearly show that the ISL0 algorithm can estimate the ISI sparse channel much better in both signal noise ratio （SNR） and compression levels. In the same channel conditions, ISL0 algorithm has been greatly improved when compared with the SL0 algorithm and other compressed-sensing algorithms.

关键词： compressed-sensing channel model ISI improved SLO algorithm sparse channel estimation MIMO system

Photoacoustic molecular imaging with functional nanoparticles

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Journal of Innovative Optical Health Sciences 2017年第4期10卷 17-28页

作者： Liming liu Huan Qin Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science College of Biophotonics South China Normal UniversityGuangzhou 510631P.R.China

Photoacoustic imaging(PAI)breaks through the optical di®usion limit by making use of the PA e®*** converting incident photons into ultrasonic waves,PAI combines high contrast of optical imaging and high spatial resolution in depth tissue of ultrasound imaging in a single imaging *** imaging modality has now shown potential for molecular imaging,which enables visualization of biological processes with systemically introduced functional *** the current review,the potentials of di®erent optical nanoprobes as PAI contrast agents were elucidated and discussed.

关键词： Photoacoustic imaging optical nanoprobes molecular imaging

Lagrangian description of nonlinear chromatography

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Science China Chemistry 2004年第6期47卷 443-452页

作者： LIANG Heng liu Xiaolong The Key Laboratory of Biomedical Information Engineering of Education Ministry Separation Science InstituteXi'an Jiaotong University Xi'an 710049 China The Key Laboratory of Biomedical Information Engineering of Education Ministry Separation Science InstituteXi'an Jiaotong University Xi'an 710049 China

Under the framework of non-equilibrium thermodynamic separation theory (NTST), Local Lagrangian approach (LLA) was proposed to deal with the essential issues of the convec- tion and diffusion (shock waves) phenomena in nonlinear chromatography with recursion equa- tions based on the three basic theorems, Lagrangian description, continuity axiom and local equilibrium assumption (LEA). This approach remarkably distinguished from the system of con- temporary chromatographic theories (Eulerian description-partial differential equations), and can felicitously match modern cybernetics.

关键词： nonlinear chromatography, Lagrangian description, recursion equations, convection-diffusion equations, shock waves.