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Non-degeneracy of extremal points in multi-dimensional space

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Science China Mathematics 2015年第11期58卷 2255-2260页

作者： cheng ChongQing ZHOU min Department of Mathematics Nanjing University School of Information Management Nanjing University

For a family of smooth functions defined in multi-dimensional space,we show that,under certain generic conditions,all minimal and maximal points are non-degenerate.

关键词： non-degeneracy multi-dimensionM space smooth functions minimal and maximal points

Motion control of multi-actuator hydraulic systems for mobile machineries： Recent advancements and future trends

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Frontiers of Mechanical Engineering 2018年第2期13卷 151-166页

作者： Bing XU min cheng The State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang University Hangzhou 310027 China The State Key Laboratory of Mechanical Transmissions School of Mechanical Engineering Chongqing University Chongqing 400044 China

This paper presents a survey of recent advancements and upcoming trends in motion control technologies employed in designing multi-actuator hydraulic systems for mobile machineries. Hydraulic systems have been extensively used in mobile machineries due to their superior power density and robustness. However, motion control technologies of multi-actuator hydraulic systems have faced increasing challenges due to stringent emission regulations. In this study, an overview of the evolution of existing throttling control technologies is presented, including open-center and load sensing controls. Recent advancements in energy-saving hydraulic technologies, such as individual metering, displacement, and hybrid controls, are briefly summarized. The impact of energy-saving hydraulic technologies on dynamic perfor- mance and control solutions are also discussed. Then, the advanced operation methods of multi-actuator mobile machineries are reviewed, including coordinated and haptic controls. Finally, challenges and opportunities of advanced motion control technologies are presented by providing an overall consideration of energy efficiency, controllability, cost, reliability, and other aspects.

关键词： motion control electrohydraulic control energy efficiency mobile machineries

Geochemical characteristics of Lower Permian coal-measure source rocks in Northeast Ordos Basin

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Chinese Journal Of Geochemistry 2014年第4期33卷 411-418页

作者： cheng Xiong ZHANG min Key Laboratory of Exploration Technology for Oil and Gas Research Ministry of Education Yangtze University School of Earth Environment and Water Resources Yangtze University

General characteristics and biomarker distributions of Lower Permian coal-measure source rocks in northeastern Ordos Bsain have been analyzed in this paper. The results show that the source rocks are type Ⅲ kerogen, thermally mature, with high content of total organic carbon. The extracts of the source rock samples with different lithologies from Well Su 27 feature high Pr/Ph ratios, high C19 TT and C24 Te, high rearranged hopanes, a predominance of C29 sterane in regular steranes, and the absence of C30 4-methylsteranes. These data suggest that the source rocks were deposited in suboxic to oxic conditions with dominantly terrigenous higher plant input. In contrast, the source rocks from wells Shuang 1 and yu 20, are characterized by low Pr/Ph ratios, low C19 TT and C24 Te, high C23 TT, similar content of C27 sterane and C29 sterane, and the presence of C30 4-methylsteranes, showing that the source rocks were deposited in reducing environment with algae and/or microorganisms and terrigenous higher plant input.

关键词：煤系烃源岩地球化学特征鄂尔多斯盆地下二叠统东北部 4-甲基甾烷高等植物生物标志物

Physical Simulation of Molten Slag Granulation by Rotary Disk

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Journal of Iron and Steel Research International 2013年第9期20卷 26-32页

作者： min Yi HUANG Jian LIU cheng-jun JIANG Mao-fa yu Xue-qing School of Materials and Metallurgy Northeastern University Benxi Steel Group Corporation

A physical model of molten slag granulation by rotary disk was developed based on the mechanism of New-tonian liquid granulation. For geometrical similarity, the radius ratio of model disk to the prototype disk was chosen as 1 ： 1. For dynamic similarity, equality of Ohnesorge number between the model and the prototype was achieved firstly by compounding rosin and paraffin wax with mass ratio of 4 ~ 1 as simulation liquid of molten blast furnace （BF） slag, and the simulation material can satisfy the similarity of liquid solid transformation during falling in the medium; then equality of Reynolds number and Weber number was obtained by controlling the volumetric flow rate and the rotary speed, respectively. Model accuracy was verified by comparing the simulation data with the results re ported in literature, which showed good agreement with the calculation results of empirical equation and the actual molten BF slag granulation from the view point of particle size. Furthermore, influences of disk radius, rotary speed and liquid flow rate on granulation were discussed using the developed model, and the Kitamura equation was modi-fied according to the simulation data which can predict particle size more accurately. Using the modified equation, the operation parameters were predicted according to the flow rate of molten industrial BF slag.

关键词： physical model simulation liquid molten slag granulation rotary disk

An experimental study on embankment failure induced by prolonged immersion in floodwater

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Water Science and Engineering 2016年第1期9卷 81-86页

作者： yu-long Luo cheng Zhang min Nie Mei-li Zhan Jin-chang Sheng College of Water Conservancy and Hydropower Engineering Hohai University

Prolonged immersion in floodwater is one of the main causes of embankment failure or dam breaks, although failure mechanisms have not been extensively studied. In this study, an embankment model was constructed to investigate the influence of prolonged immersion in floodwater on the failure of an embankment. The results indicate that：（1） the phreatic surface gradually rises and negative pore pressures gradually dissipate with the time of prolonged immersion in floodwater, and, finally, a stable and fully saturated state is reached; （2） observable cracks and a heave phenomenon are found near the downstream toe and in the top stratum of the foundation, which are attributed to the large uplift pressure on the interface between the top stratum and the pervious substratum, the tremendous impact effect induced by the rapid rise in water level, and the reduction of shear strength of heavy silt loam. The present study enhances our in-depth knowledge of the mechanisms of embankment failure induced by floodwater, and provides experimental data for validation of mathematical models of the embankment seepage failure.

关键词： Embankment Floodwater Seepage failure Prolonged immersion Heave phenomenon

Effects of Vegetation Succession on Soil Fertility Within Farming-Plantation Ecotone in Ziwuling Mountains of the Loess Plateau in China

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Agricultural Sciences in China 2010年第10期9卷 1481-1491页

作者： LIANG Jian WANG Xiao-an yu Zhong-dong DONG Zhong-min WANG Jin-cheng School of Life Sciences Shaanxi Normal University Xi'an 710062 P.R.China College of Forestry Northwest A&F University Yangling 712100 P.R. China Department of Biology Saint Mary 's University Halifax B3H 3C3 Canada

To further understand the relationship between vegetation succession and soil fertility within farming-plantation ecotone in Ziwuling Mountains of the Loess Plateau, nine kinds of widely distributed communities at different succession stages were selected, and the effects of vegetation succession on soil fertility were studied through the methods of comparing two hierarchical clustering （similarity index： B） and other multivariate analysis. The results showed that：（i） the similarity in clustering pattern of nine communities which classified by plant species and soil nutrients respectively showed a trend of B ^-overall plant-soil0-10cn〉B^-overall plant-soil 10-20 cm 〉B^- overall plant-soil 20-40 cm, and for the top soil, it showed a trend of B^- grass-soil 0-10 cm 〉 B^-shrub-soil 0-10 cm 〉 Btree-soil0-10 cm; （ii） soil fertility increased during the succession process from abandoned land to forest community, and the soil fertility of forest community showed an increased order of coniferous forest →mixed forest →broadleaf forest; （iii） during the process of vegetation succession, the variation of topsoil fertility was higher than that of the subsurface soil （coefficient of variation： CV0-10 cm 〉CV 10-20 cm 〉 CV20-40 cm）, and when the succession developed into the stages of shrub and forest communities, the top soil fertility had been improved significantly; and （iv） for the subsurface soil of the communities at the advanced succession stages, the soil fertility also increased to some extent. Our results suggested that the method of comparing two hierarchical clustering reflected the similarity level of different cluster patterns, therefore, it was helpful to study the relationship between vegetation succession and soil fertility. There was a corresponding relationship between the change process of soil fertility from the top soil to subsurface soil and the process of vegetation succession from the early stages to the advanced stage. The differentiations of soil fertil

关键词： vegetation succession soil fertility vegetation-soil communities multivariate statistical analysis LoessPlateau

Simulation of the erosion of casing and perforation under staged sand fracturing conditions in horizontal sections

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Journal of Hydrodynamics 2022年第4期34卷 725-743页

作者： Bao-cheng Wu Si-song Zhang Jian-min Li yu-ting Pan De-zhi Zeng Hui-yong yu Hong-jun Zhu Research Institute of Engineering Technology PetroChina Xinjiang Oilfield CompanyKaramay 834000China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu 610500China

The new fracturing technology of intensive stages and high-intensity proppant injection shows significant advantages of cost reduction and high efficiency in the volume fracturing of unconventional reservoirs,but it also intensifies the erosion of the casing and the perforations,with a perforation diameter expansion and the casing wall *** solve this problem,in view of the applications of the perforation fracturing technology under the construction conditions in Mahu Area in Xinjiang,China,the structure parameters of the downhole strings are measured and a calculation model of the perforation casing erosion is established for the large-displacement sand fracturing process in horizontal *** software ANSYS-FLUENT is used to simulate the casing and perforation erosion under different conditions of the displacement,the sand content,the proppant particle size,and the fracturing fluid viscosity in the sand fracturing *** particle size of the proppant and the viscosity of the fracturing fluid mainly affect the erosion area,but they have little influence on the erosion *** sand content and the displacement significantly affect the erosion *** these factors,the sand content has a more significant effect on the erosion rate and the displacement has a more significant effect on the erosion *** to the influence of gravity,the perforation erosion rate is larger when the phase angle ranges from 120°to 240°.

关键词： Sand fracturing erosion numerical simulation perforated casing solid-liquid flow

Enhancing betavoltaic nuclear battery performance with 3D P^(+)PNN^(+)multi-groove structure via carrier evolution

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Nuclear Science and Techniques 2023年第12期34卷 1-16页

作者： Hou‑Jun He yun‑cheng Han Xiao‑yu Wang yu‑min Liu Jia‑Chen Zhang Lei Ren ming‑Jie Zheng Hefei Institutes of Physical Science Chinese Academy of SciencesHefei 230031China University of Science and Technology of China Hefei 230026China School of Nuclear Science and Engineering East China University of TechnologyNanchang 330013China School of Nuclear Technology and Chemistry and Biology Hubei University of Science and TechnologyXianning 437100China

Betavoltaic nuclear batteries offer a promising alternative energy source that harnesses the power of beta particles emitted by *** satisfy the power demands of microelectromechanical systems(MEMS),3D structures have been proposed as a potential ***,this paper introduces a novel 3D^(63)Ni–SiC-based P^(+)PNN^(+)structure with a multi-groove design,avoiding the need for PN junctions on the inner surface,and thus reducing leakage current and power *** Carlo simulations were performed considering the fully coupled physical model to extend the electron–hole pair generation rate to a 3D structure,enabling the efficient design and development of betavoltaic batteries with complex 3D *** a result,the proposed model produces the significantly higher maximum output power density of 19.74μW/cm^(2) and corresponding short-circuit current,open-circuit voltage,and conversion efficiency of 8.57μA/cm^(2),2.45 V,and4.58%,respectively,compared with conventional planar *** analysis of the carrier transport and collection characteristics using the COMSOL Multiphysics code,we provide deep insights regarding power increase,and elucidate the discrepancies between the ideal and simulated performances of betavoltaic *** work offers a promising approach for the design and optimization of high-output betavoltaic nuclear batteries with a unique 3D design,and serves as a valuable reference for future device fabrication.

关键词： Betavoltaic nuclear battery High-output power density Three-dimensional structure Carrier drift–diffusion Carrier recombination Carrier collection efficiency

Analytical Criteria for Local Activity of CNN with Two-port and Application to Biochemical Model

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International Journal of minerals,Metallurgy and Materials 2000年第4期14卷 305-314页

作者： Lequan min Na yu Applied Science School University of Science and Technology BeijingBeijing 100083China

The analytic criteria are presented for the local activity theory in two-port Cellular Neural Network (CNN) cells with three local state variables, and the application to a Biochemical Model CNN (BMCNN) is given for coupling in series of two enzymes whose prototype was studied by Decroly and Goldbeter. The bifurcation diagrams of the BMCNN's show that there does not exist a locally passive domain, and the computer simulation exhibited that convergent patterns, oscillatory patterns or chaotic patterns may emerge if the selected cell parameters are located in locally active unstable domains but nearby the edge of chaos domain. In particular, the coexistence of multiple oscillations was observed in the corresponding triple cell couples of the BMCNN's with the same initial conditions.

关键词： Cellular neural networks