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Mean-square exponential stability of stochastic Volterra systems in infinite dimensions

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Science China(Information Sciences) 2024年第10期67卷 298-314页

作者： Lin FU Shiguo PENG Feiqi DENG Quanxin zhu School of Automation Guangdong University of Technology School of Automation Science and Engineering South China University of Technology Key Laboratory of Computing and Stochastic Mathematics(Ministry of Education) School of Mathematics and StatisticsHunan Normal University

Over the past decade, the study of stability theory in integro-differential systems has grown significantly owing to their relevance in solving physical and engineering problems, such as viscoelasticity and thermo-viscoelasticity in materials with memory properties. This paper concentrates on a class of infinite-dimensional stochastic integro-differential systems. We establish the well-posedness of the system and identify mild solutions to the system and an abstract stochastic Cauchy problem. This identification is identified by employing a semigroup approach combined with Yosida approximation. We derive sufficient conditions that ensure the mean-square exponential stability of mild solutions to the system boils down to the boundedness of a certain function and a norm estimate for the stochastic part. These conditions are implemented through the semigroup approach and the composition operator method. Illustrative examples are provided and the obtained theoretical results are validated by numerical simulations.

关键词： stochastic integro-differential equations mean-square exponential stability stochastic distributed parameter systems Hardy space composition operators

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A settling curve modeling method for quantitative description of the dispersion stability of carbon nanotubes in aquatic environments

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Journal of Environmental Sciences 2015年第3期27卷 1-10页

作者： Lixia Zhou Dunxue zhu Shujuan Zhang bingcai Pan State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University

Understanding the aggregation and deposition behavior of carbon nanotubes （CNTs） is of great significance in terms of their fate and transport in the environment. Attachment efficiency is a widely used index for well-dispersed CNT solutions. However, in natural waters, CNTs are usually heterogeneous in particle size. The attachment efficiency method is not applicable to such systems. Describing the dispersion stability of CNTs in natural aquatic systems is still a challenge. In this work, a settling curve modeling （SCM） method was developed for the description of the aggregation and deposition behavior of CNTs in aqueous solutions. The effects of water chemistry （natural organic matter, pH, and ionic strength） on the aggregation and deposition behavior of pristine and surface-functionalized multi-walled carbon nanotubes （MWCNTs） were systematically studied to evaluate the reliability of the SCM method. The results showed that, as compared to particle size and optical density, the centrifugal sedimentation rate constant （ks） from the settling curve profile is a practical, useful and reliable index for the description of heterogeneous CNT suspensions. The SCM method was successfully applied to MWCNT in three natural waters. The constituents in water, especially organic matter, determine the dispersion stability of MWCNTs in natural water bodies.

关键词： Settling curveCarbon nanotubesHeterogeneousCentrifugal sedimentationrate constant

Directionality based fast fractional pel motion estimation for H.264

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Journal of Systems Engineering and Electronics 2009年第3期20卷 457-462页

作者： Zhang Wei Fan Fen Wang Xiaoyang zhu Weile School of Electronic Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

Motion estimation is an important and intensive task in video coding applications. Since the complexity of integer pixel search has been greatly reduced by the numerous fast ME algorithm, the computation overhead required by fractional pixel ME has become relatively significant. To reduce the complexity of the fractional pixel ME algorithm, a directionality-based fractional pixel ME algorithm is proposed. The proposed algorithm efficiently explores the neighborhood positions which with high probability to be the best matching around the minimum one and skips over other unlikely ones. Thus, the proposed algorithm can complete the search by examining only 3 points on appropriate condition instead of 17 search points in the search algorithm of reference software. The simulation results show that the proposed algorithm successfully optimizes the fractional-pixel motion search on both half and quarter-pixel accuracy and improves the processing speed with low PSNR penalty.

关键词： fast encoding fractional pel motion search

Quaternary integrative stratigraphy and timescale of China

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Science China Earth Sciences 2019年第1期62卷 324-348页

作者： Chenglong DENG Qingzhen HAO Zhengtang GUO Rixiang zhu State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Institutions of Earth Science Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences Key Laboratory of Cenozoic Geology and Environment Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences

Quaternary strata in China mainly comprise continental deposits in a variety of depositional settings. The continental Quaternary in temperate northern China consists mainly of eolian and fluvio-lacustrine deposits; that in subtropical southern China, mainly of vermiculated red soils, cave/fissure deposits, and fluvio-lacustrine deposits; and that in the alpine Tibetan Plateau, mainly of fluvio-lacustrine and piedmont deposits. The marine Quaternary in China consists of detrital deposits and biogenic reef deposits. The integration of biostratigraphy, magnetostratigraphy, climatostratigraphy and an astronomically calibrated chronology has led to the establishment of high-precision climatochronostratigraphic timescales for the detrital marine Quaternary in the South China Sea and the loess-paleosol sequence in the Chinese Loess Plateau. Extremely high-precision230 Th dating has provided a high-precision absolute age model for cave stalagmites over the past 640000 years as well as highresolution oxygen isotope records representing orbital-to suborbital-scale climate changes. By combining magnetic stratigraphy and biostratigraphy, robust chronostratigraphic frameworks for non-eolian continental Quaternary deposits on the scale of Quaternary geomagnetic polarities have been established. The continental Pleistocene Series consists, from oldest to youngest,of the Nihewanian Stage of the Lower Pleistocene, the Zhoukoudianian Stage of the Middle Pleistocene, and the Salawusuan Stage of the Upper Pleistocene. Stages of the continental Holocene Series have not yet been established. This review summarizes recent developments in the Quaternary chronostratigraphy of representative Quaternary strata and associated faunas, and then proposes an integrative chronostratigraphic framework and a stratigraphic correlation scheme for Quaternary continental strata in China. In the near-future, it is hoped to establish not only a Chinese continental Quaternary climatochronostratigraphic cha

关键词： Quaternary Chronostratigraphy Magnetic stratigraphy biostratigraphy Climatostratigraphy China

Transport mechanisms of contaminants released from fine sediment in rivers

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Acta Mechanica Sinica 2015年第6期31卷 791-798页

作者： Pengda Cheng Hongwei zhu Baochang Zhong Daozeng Wang Institute of Mechanics Chinese Academy of Sciences Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

Contaminants released from sediment into rivers are one of the main problems to study in environmental hydrodynamics. For contaminants released into the overlying water under different hydrodynamic conditions, the mechanical mechanisms involved can be roughly divided into convective diffusion, molecular diffusion, and adsorption/desorption. Because of the obvious environmental influence of fine sediment （D90 = 0.06 mm）, non-cohesive fine sediment, and cohesive fine sediment are researched in this paper, and phosphorus is chosen for a typical adsorption of a contaminant. Through theoretical analysis of the contaminant release process, according to different hydraulic conditions, the contaminant release coupling mathematical model can be established by the N-S equation, the Darcy equation, the solute transport equation, and the adsorption/desorption equation. Then, the experiments are completed in an open water flume. The simulation results and experimental results show that convective diffusion dominates the contaminant release both in non-cohesive and cohesive fine sediment after their suspension, and that they contribute more than 90 % of the total release. Molecular diffusion and desorption have more of a contribution for contaminant release from unsuspended sediment. In unsuspension sediment, convective diffusion is about 10-50 times larger than molecular diffusion during the initial stages under high velocity; it is close to molecular diffusion in the later stages. Convective diffusion is about 6 times larger than molecular diffusion during the initial stages under low velocity, it is about a quarter of mole- cular diffusion in later stages, and has a similar level with desorption/adsorption. In unsuspended sediment, a seepage boundary layer exists below the water-sediment interface, and various release mechanisms in that layer mostly dominate the contaminant release process. In non-cohesive fine sediment, the depth of that layer increases linearly with shear st

关键词： Cohesive Diffusion Seepage boundarylayer. Adsorption/desorption Coupling

Hierarchical-Based Object Detection with Improved Locality Sparse Coding

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Chinese Journal of Electronics 2016年第2期25卷 290-295页

作者： zhu Suguo DU Junping REN Nan LIANG Meiyu Beijing Key Laboratory of Intelligent Telecommunication software and Multimedia School of Computer ScienceBeijing University of Posts and Telecommunications

This paper proposes to extend the hierarchical method to be adapted to sequential frames, aiming at detecting the moving object in dynamic scenes. A novel two-layer model is proposed, in which dictionaries are learned through three different stages and the locality constrained sparse representation is improved. This leads more significant improvement for performance of both static image classification and moving object detection. The experimental results demonstrate that the proposed algorithm is efficient and robust compared with the state-of-the-art classification methods, and also able to detect moving object in the sequential frames accurately.

关键词： Hierarchical detection Sparse coding Classification Object detection

Reduction of low-grade manganese oxide ore by biomass roasting

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Acta Metallurgica Sinica(English Letters) 2010年第3期23卷 223-229页

作者： Jingjing SONG Guocai zhu Ping ZHANG Yuna ZHAO Institute of Nuclear and New Energy Technology Tsinghua University Beijing 102201 China College of Material Science and Chemistry Engineering China University of Geosciences Wuhan 430074 China

The reduction process of manganese dioxide in low-grade manganese ore by biomass roasting was *** calcine of manganese oxide ore was further leached by sulphuric acid, the manganese in ore can be converted into manganese *** of the mass ratio of manganese ore to sawdust, roasting temperature and time, leaching temperature and time, leaching agent concentration and liquid-solid ratio were studied.97.71% of manganese recovery can be achieved under the optimal conditions：the mass ratio of manganese ore to sawdust of 5：1, roasting temperature at 500℃ for 40 min, leaching temperature at 60℃ for 40 min, sulphuric acid concentration of 1 mol/L and liquid-solid ratio of 10：*** types of low-grade manganese ore like Guilin ore, Nanning ore and Gongcheng ore were tested and the same results were obtained.

关键词： Reduction roasting Manganese oxide ore biomass

Dynamic Recrystallization Behavior of a Heat-resistant Martensitic Stainless Steel 403Nb during Hot Deformation

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Journal of Materials Science & Technology 2011年第10期27卷 913-919页

作者： Zhouyu Zeng Liqing Chen Fuxian zhu Xianghua Liu State Key Laboratory of Rolling and Automation Northeastern University 3-11 Wenhua Road Shenyang 110819 China

Dynamic recrystallization （DRX） behaviors of a heat-resistant martensitic stainless steel 403Nb during hot deformation have been investigated by single-pass thermo-mechanical simulative experiment at temperatures of 900-1150℃ and strain rates of 0.01-1 s-1 The results show that the true stress-true strain curves of this alloy can be classified into two types, one is of dynamic recovery and the other is of dynamic recrystallization. The DRX in 403Nb alloy is easy to occur at strain rates lower than 0.5 s-1 and deformation temperatures higher than 1000℃. Using regression analysis, the stress multiplier （a） and apparent stress exponent （n） were calculated to be 0.0153 and 3.22, respectively, while the activation energy （Qd） for DRX of 403Nb was calculated to be 367.293 kJ/mol. The constitutive equation of peak stress for DRX was also obtained. Based on P-J method, the critical strain for DRX was accurately determined. The mathematical models of peak strain and kinetic equation for DRX of 403Nb steel were finally established.

关键词： 403Nb steel Dynamic recrystallization Hot deformation Critical strain

Electrochemical migration behavior of Ag-plated Cu-filled electrically conductive adhesives

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Rare Metals 2012年第1期31卷 64-70页

作者： zhu, Xiaoyun Liu, Yuanlong Long, Jinming Liu, Xiaoli School of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 China Faculty of Metallurgy and Energy Engineering Kunming University of Science and Technology Kunming 650093 China

The electrochemical migration (ECM) behavior of the electrically conductive adhesives (ECAs) filled with pure Ag powder or Ag-plated Cu composite powder with varied Ag:Cu ratios was investigated under the condition of applying constant voltage and distilled water *** resistance was determined from the current-time *** microstructure and composition of ECM dendrite products were analyzed by SEM/EDS and *** was found that the ECM resistance of Ag-plated Cu composite powder-filled ECAs was evidently higher than that of pure Ag powder-filled *** Ag:Cu ratio of composite powder in ECAs had notable influence on ECM resistance,which was enhanced with the decrease of Ag:Cu *** composition of dendrites formed between cathode and anode during ECM process was not uniform for Ag-plated Cu-filled *** ECM inhibiting mechanism of Ag-plated Cu composite powder was proposed according to analysis of the electrochemical impedance spectroscopy,Tafel plot and dendrite composition.

关键词： composite material electrochemical migration Ag-plated Cu composite powder electrically conductive adhesives