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DPTM simulation of aeolian sand ripple

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Science China(Physics,Mechanics & Astronomy) 2008年第3期51卷 328-336页

作者： zheng XiaoJing bo Tianli xie li Key Laboratory of Mechanics on Western Disaster and Environment Lanzhou UniversityLanzhou 730000China

Aeolian sand ripple and its time evolution are simulated by the discrete particle tracing method (DPTM) presented in this paper. The difference between this method and the current methods is that the former can consider the three main factors relevant to the formation of natural aeolian sand ripples,which are the wind-blown sand flux above the sand bed formed by lots of sand particles with different di-ameters,the particle-bed collision and after it the rebound and ejection of sand particles in the sand bed,the saltation of high-speed sand particles and the creep of low-speed sand particles,respectively. The simulated aeolian sand ripple is close to the natural sand ripple not only in basic shape and characteristic,particle size segregation and stratigraphy,but also in formation stages. In addition,three important speeds can be obtained by this method,which are the propagation speed of the saturated aeolian sand ripple and the critical frictional wind speeds of emergence and disappearance of sand ripple.

关键词： wind-blown sand flux aeolian sand ripple discrete particle tracing method (DPTM) mixed-particle-size creep

Wavelength dependent loss of splice of single-mode fibers

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Journal of Central South University 2013年第7期20卷 1832-1837页

作者： YANG bo DUAN Ji-an xie zheng XIAO hong-feng State Key Laboratory of High Performance Complex Manufactory (Central South University) Changsha 410083 China Institution of Image Recognition and Computer Vision Hunan Normal University Changsha 410081 China

After reviewing three different definitions of mode field diameter of single-mode fibers, coupled efficiency calculation methods associated with lateral offset, longitude separation and wavelength, the effects produced by them, and the influences of splicing defects were discussed in detail. The regularities of the effects were studied according to the first order derivation of couple efficiency formula, and a simplified formula for couple efficiency calculation was presented under the circumstance of slight misalignment, with respect to wavelength, 2, and in a good agreement with the theoretical model. The simplified formula provides a new but simple approach to evaluate wavelength dependent couple efficiency of single-mode fibers. Theoretical analyses and numerical calculations show that, when those defects exist, the wavelength produces additional effects on the couple loss that growth of wavelength causes an increase on the couple efficiency for the lateral offset or longitude separation whereas lessens the couple efficiency due to angular misalignment or mode fields mismatching, and that the wavelength degrades the couple efficiency distinctly when λ≥2.5 μm whereas it distorts the couple slightly in range of λ≤2λ≤2 μm.

关键词： wavelength dependent loss couple efficiency single-mode fiber cut-offwavelength

Millennial climate changes since MIS 3 revealed by element records in deep-sea sediments from northern South China Sea

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Chinese Science Bulletin 2014年第8期59卷 776-784页

作者： Xin xie hong-bo zheng Pei-Jun Qiao State Key Laboratory of Marine Geology Tongji University School of Geography Science Nanjing Normal University

High resolution elemental records in core MD05-2903 from the northern South China Sea were obtained from XRF scanning and grain size and mineral component *** K/Ti curve reveals climate changes since MIS 3 on a millennial scale,representing one of the best such records so far from deep-sea sediments of the South China *** compared our K/Ti record with other climate records from high latitude ice cores and from East Asia stalagmites,variations in the K/Ti record show some typical saw-shaped features of rapid climate changes in the Northern *** size analysis reveals a close relationship between variations in K/Ti and in the fine end-member grain *** analysis confirms that high K/Ti layers were dominated by K-rich weathering minerals,especially illite,while low K/Ti layers contain low illite but high abundance of Ti-rich heavy ***,the K/Ti record reflects changes in the input and deposition of fine weathering minerals and heavy minerals in the northern South China Sea region during stadials and *** elemental changes were largely controlled by variations in rainfall,erosion,and fluvial transportation induced by East Asia Monsoon.

关键词：深海沉积物中国南海气候变化 MIS 元素显示 X射线衍射分析矿物风化

Unraveling the morphological evolution mechanism of solid sulfur species in lithium-sulfur batteries with operando light microscopy

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Journal of Energy Chemistry 2022年第10期31卷 460-468,I0012页

作者： Jingqiang zheng Chaohong Guan Huangxu li Yangyang xie Junxian Hu Kai Zhang bo hong Yanqing Lai Jie li Zhian Zhang School of Metallurgy and Environment Hunan Province Key Laboratory of Nonferrous Value-Added MetallurgyCentral South UniversityChangsha 410083HunanChina University of Michigan-Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong UniversityShanghai 200240China Department of Chemistry City University of Hong KongKowloonHong Kong 999077China

Solid-liquid phase conversion between various sulfur species in lithium-sulfur(li-S)batteries is a fundamental reaction of the sulfur *** the morphological evolution of solid sulfur species upon cycling is of great significance to achieving high energy ***,an in-depth investigation of the internal reaction is still *** this work,the evolution process of solid sulfur species on carbon substrates is systematically studied by using an operando light microscope combined with in situ electrochemical impedance spectra *** observation of phenomena such as bulk solid sulfur species can form and dissolve independently of the conductive substrates and the transformation of supercooled liquid sulfur to crystalline *** on the phenomena mentioned above,a possible mechanism was proposed in which the dissolution reaction of solid sulfur species is a spatially free reaction that involves isotropic physical dissolution,diffusion of molecules,and finally the electrochemical ***,the formation of solid sulfur species tends to be a form of crystallization in a saturated solution rather than electrodeposition,as is commonly *** findings offer new insights into the reaction of sulfur cathodes and provide new opportunities to design advanced sulfur cathodes for li-S batteries.

关键词： lithium-sulfur batteries Morphological evolution Supercooled liquid sulfur Operando light microscopy liquid sulfur droplets

Precise trajectory tracking of mecanum-wheeled omnidirectional mobile robots via a novel fixed-time sliding mode control approach

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Control Theory and Technology 2024年第4期22卷 596-611页

作者： Zhe Sun Zhipeng li Hao xie Yunjun zheng Jinchuan zheng bo Chen College of Information Engineering Zhejiang University of TechnologyHangzhou310023China School of Science Computing and Engineering TechnologiesSwinburne University of TechnologyHawthorn3122VICAustralia School of Mechanical Engineering Hefei University of TechnologyHefei230009AnhuiChina

This paper proposes a novel fixed-time sliding mode control approach for trajectory-tracking tasks of a mecanum-wheeled omnidirectional mobile ***,the idea of two-phase attractors is introduced into the domain of sliding mode control,and a new fixed-time sliding surface is ***,according to this sliding surface,a new type of nonsingular fast terminal sliding mode control algorithm is designed for the omnidirectional mobile robot,which can realize a fast fixed-time convergence *** stability of the control system is proven scrupulously,and a guideline for control-parameter tuning is ***,experiments are implemented to test the trajectory-tracking performance of the *** results demonstrate the superiority of the proposed sliding surface and the corresponding control scheme in comparison with benchmark controllers.

关键词： Omnidirectional mobile robot Trajectory tracking Sliding mode control Fixed-time convergence

An efficient projection defocus algorithm based on multi-scale convolution kernel templates

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Journal of Zhejiang University-Science C(Computers and Electronics) 2013年第12期14卷 930-940页

作者： bo ZHU li-jun xie Guang-hua SONG Yao zheng School of Aeronautics and Astronautics Zhejiang University Center for Engineering and Scientific Computation Zhejiang University

The focal problems of projection include out-of-focus projection images from the projector caused by incomplete mechanical focus and screen-door effects produced by projection pixilation. To eliminate these defects and enhance the imaging quality and clarity of projectors, a novel adaptive projection defocus algorithm is proposed based on multi-scale convolution kernel templates. This algorithm applies the improved Sobel-Tenengrad focus evaluation function to calculate the sharpness degree of intensity equalization and then constructs multi-scale defocus convolution kernels to remap and render the defocus projection image. The resulting projection defocus corrected images can eliminate out-of-focus effects and improve the sharpness of uncorrected images. Experiments show that the algorithm works quickly and robustly and that it not only effectively eliminates visual artifacts and can run on a self-designed smart projection system in real time but also significantly improves the resolution and clarity of the observer's visual perception.

关键词： Projection focal Sobel-Tenengrad evaluation function Projector defocus Multi-scale convolution kernels

Can Classic Avrami Theory Describe the Isothermal Crystallization Kinetics for Stereocomplex Poly(lactic acid)?

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Chinese Journal of Polymer Science 2017年第6期35卷 773-781页

作者：谢兰 Xu-juan li 熊玉竹 Qin Chen Hai-bo xie Qiang zheng Department of Polymer and Processing College of Materials and MetallurgyGuizhou UniversityGuiyang 550025China College of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China

Classic Avrami model and its modifications have found diverse applications in describing the thermal and phase behaviors of inorganic metals and organic polymers. The direct introduction of classic Avrami equation to offer quantitative analyses of crystallization kinetic parameters for enantiomeric poly（lactic acid）（PLA） blends may, however, lead to contradictory conclusions. As revealed by this study, during the characterization of isothermal melt and cold crystallization for stereocomplex PLA containing equal-weight poly（L-lactic acid） and poly（D-lactic acid）, the kinetic parameters yielded by Avrami equation are not in line with the classic crystallization hypotheses or the direct morphological observations. The underlying mechanisms, to some extent, lie in the generation of stereocomplex crystals （SCs） during the cooling/heating which affects the subsequent crystallization dynamics. The huge gap between the melting enthalpies of 100% crystalline SCs （142 J/g） and homo-crystals （HCs, 93 J/g） is most likely responsible for the confusing kinetic parameters acquired from the deduction of Avrami equation, which is based on the integration of enthalpies as a function of crystallization time. This prompts for great care that the classic Avrami equation is not applicable to accurately describe the crystallization kinetics of stereocomplex PLA, given the generation of SCs prior to crystallization and the coexistence of HCs and SCs during crystallization.

关键词： Poly(lactic acid) Stereocomplex crystallization Crystallization kinetics Classic Avrami theory

Genome-wide identification and characterization of ACBP gene family in Populus reveal salinity alkali-responsive profiles

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Journal of Forestry Research 2023年第2期34卷 481-496页

作者： Yu Chang Xinru Xu hongxia zheng Hao xie bo li Sixue Chen Ying li Shaojun Dai Key Laboratory of Saline-Alkali Vegetation Ecology Restoration(Northeast Forestry University) Ministry of EducationCollege of Life SciencesNortheast Forestry UniversityHarbin 150040People’s Republic of China Development Center of Plant Germplasm Resources College of Life SciencesShanghai Normal UniversityShanghai 200234People’s Republic of China Department of Biology Genetics InstitutePlant Molecular and Cellular Biology ProgramInterdisciplinary Center for Biotechnology ResearchUniversity of FloridaGainesvilleFloridaUSA

Acyl-CoA-binding proteins(ACBPs)are important for the transport of acyl groups for macro molecular biosynthesis involved in plant growth,development,and diverse stress(e.g.,cold,drought,salinity,and heavy metals)***,we report the phylogeny and characteristics of the ACBP family in the woody plant Populus *** genes encoding ACBP proteins were identified,and they are distributed on eight chromosomes in *** PtACBP genes were divided into four subgroups according to gene structure,conserved motifs and phylogenetic *** analysis revealed that cis-elements were related to stress response,phytohormone response,and physical and reproductive growth *** levels of PtACBP genes varied among different organs,with the highest expression in leaves and the lowest in *** real-time PCR(qRT-PCR)analysis showed that under salinity-alkali stresses(i.e.,200 mM NaCl,75 mM Na2CO3,and 100 mM NaHCO3),four(PtACBP1,PtACBP3,PtACBP4 and PtACBP8)of eight PtACBP genes were significantly induced in roots and *** data provide a comprehensive analysis of the ACBPs family in ***,which could be useful for gene function analyses.

关键词： Acyl-CoA-binding proteins(ACBPs) Gene structure Expression pattern Stress response Populus trichocarpa

Commentary of research situation and innovation frontier in hydro-structure engineering science

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Science China(Technological Sciences) 2011年第4期54卷 767-780页

作者： WU ZhongRu PENG Yan li ZhanChao li bo YU hong zheng ShouRen State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai UniversityNanjing 210098China Changjiang Water Resource Commission Wuhan 430071China

In order to utilize water and hydropower resources in China,multitudes of water projects are established or to be constructed as an integral part of the national economy's *** these circumstances,there are two outstanding problems:1) a mass of existing dams are in danger and 2) in the southwest water-conservancy construction plan,dozens of existing or planned dams are high dams or even super high dams with heights between 200 and 300 *** accordance with demands of "the National Program for Medium-and Long-Term Scientific and Technological Development" on the innovation frontier in hydro-structure engineering science,various key problems in science and technology such like stress analysis,ultimate bearing capacity,nonlinearity *** high dams,super high dams and sick dams have been *** paper makes a commentary on the advances and results of the researches,then analyzes the advantages and disadvantages of current theoretics and methodologies,and finally presents corresponding research directions and the frontier of innovation.

关键词： hydro-structure engineering science research situation innovation frontier stress analysis ultimate bearing capacity nonlinearity commentary