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Identifying urban land use social functional units:a case study using OSM data

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International Journal of Digital Earth 2021年第12期14卷 1798-1817页

作者： zhen liu Aerospace Information Research Institute Chinese Academy of SciencesBeijingPeople’s Republic of China

Urban land use is always the central focus of urban planners and policymakers when pursuing urban sustainable ***,many studies have explored urban land use using satellite data,but few of them can identify the social function of land use through these *** this research,OpenStreetMap(OSM)data are used to extract urban land use social functional ***,the OSM data are transferred to actual land use types based on the established mapping rules between OSM data and the urban land use classification ***,the improved DBSCAN algorithm is applied with OSM data of the study area after estimating the parameters of the neighborhood radius(Eps)and the minimum polygons(MinPolys)based on the polygon *** the two estimated parameters,the improved DBSCAN algorithm is used to cluster residential,commercial and public service land use social functional polygons of the OSM *** that,the clusters of the three land use types are processed into land use social functional *** results show that OSM data perform well in determining these three land use social functional clusters using the improved DBSCAN algorithm,and the social functional units display obvious spatial features.

关键词： Urban land use social functional unit openstreetmap DBSCAN

Studying cost-sensitive learning for multi-class imbalance in Internet traffic classification

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The Journal of China Universities of Posts and Telecommunications 2012年第6期19卷 63-72页

作者： liu zhen liu Qiong School of Soft Engineering South China University of Technology School of Computer Science and Engineering South China University of Technology

Cost-sensitive learning has been applied to resolve the multi-class imbalance problem in Internet traffic classification and it has achieved considerable results. But the classification performance on the minority classes with a few bytes is still unhopeful because the existing research only focuses on the classes with a large amount of bytes. Therefore, the class-dependent misclassification cost is studied. Firstly, the flow rate based cost matrix （FCM） is investigated. Secondly, a new cost matrix named weighted cost matrix （WCM） is proposed, which calculates a reasonable weight for each cost of FCM by regarding the data imbalance degree and classification accuracy of each class. It is able to further improve the classification performance on the difficult minority class （the class with more flows but worse classification accuracy）. Experimental results on twelve real traffic datasets show that FCM and WCM obtain more than 92% flow g-mean and 80% byte g-mean on average; on the test set collected one year later, WCM outperforms FCM in terms of stability.

关键词： Internet traffic classification minority class cost matrix machine learning

Numerical Study on the Energy Extraction Performance of Coupled Tandem Flapping Hydrofoils

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China Ocean Engineering 2022年第1期36卷 38-49页

作者： QU Heng-liang liu zhen College of Engineering Ocean University of ChinaQingdao 266100China Shandong Provincial Key Laboratory of Ocean Engineering Ocean University of ChinaQingdao 266100China Qingdao Municipal Key Laboratory of Ocean Renewable Energy Ocean University of ChinaQingdao 266100China

Tidal current energy is a promising renewable energy source for future electricity *** flapping hydrofoil is regarded as a useful tool to extract the tidal current energy in shallow water.A concept of coupled tandem flapping hydrofoils under semi-activated mode was proposed in the present study.A two-dimensional numerical model,based on the computational fluid dynamics software ANSYS-Fluent,was established to investigate the power extraction performance of the coupled tandem flapping *** effects of the reduced frequency,pitching amplitude,moment of inertia,damping coefficient,and longitudinal distance between hydrofoils were *** vortices,pressure distribution,and kinetic characteristics of hydrofoils under various conditions were analyzed to reveal the interaction between the shedding vortex and *** energy extraction mechanism and hydrodynamic performance were *** positive interactions for energy harvesting were identified for improvements of the further *** peak values of efficiency and power coefficient were achieved at 0.69 and 2.13,respectively.

关键词： energy extraction numerical study semi-activated coupled tandem hydrofoils

Discharge characteristics of coal and extraction residue from direct coal liquefaction in partial fluidization silo

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Chinese Journal of Chemical Engineering 2022年第12期52卷 78-87页

作者： zhen liu Haiquan An Jiansheng Zhang Department of Energy and Power Engineering Tsinghua UniversityBeijing 100084China National Institute of Clean-and-Low-Carbon Energy Beijing 100084China

Gasification of extraction residue(ER) from direct coal liquefaction with pulverized coal is an efficient way for the utilization of carbonaceous wastes, which improve the overall efficiency of direct coal liquefaction technology. The discharge characteristics of ER mixing with pulverized coal is important paraments for its gasification process, which is seldom studied in the literature. In this study, the discharge characteristics of the pulverized coal(M1) as well as its mixture with ER(M2) were systematically investigated in an atmospheric pressure partial fluidization silo with different fluidization apparent velocity. It was observed that although M2 is a viscous powder with lower flowability than M1, the mass flow rate of M2 is 65% higher than M1 at the 3.7 mm·s-1apparent gas velocity. M2 exhibits the properties of Geldart A type powder, which improves the mass flow rate and stability of the discharged material. The mass flow rate of both M1 and M2 first increases and then slowly decreases with the increase of apparent gas velocity of the fluidizing air, which means the discharge process of M1 and M2 can be optimized by the apparent gas velocity.

关键词： Discharge characteristics Silo Extraction residue Direct coal liquefaction Fluidizing air

Recovery of vanadium and molybdenum from spent petrochemical catalyst by microwave-assisted leaching

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International Journal of Minerals,Metallurgy and Materials 2019年第1期26卷 33-40页

作者： Zhi-yuan Ma Yong liu Ji-kui Zhou Mu-dan liu zhen-zhen liu Guangdong Institute of Resources Comprehensive Utilization Guangdong Academy of Sciences State Key Laboratory of Separation and Comprehensive Utilization of Rare Metals Guangdong Provincial Key Laboratory of Development and Comprehensive Utilization of Mineral Resources

The study of the leaching of vanadium(V) and molybdenum(Mo) from spent petrochemical catalysts in sodium hydroxide(NaO H) medium was performed using two approaches, namely, conventional leaching and microwave-assisted leaching methods. The influence of microwave power, leaching time, leaching temperature, and NaOH concentration on the leaching efficiency of spent petrochemical catalyst was investigated. Under microwave-assisted conditions(600 W, 10 min, 90°C, 2.0 mol·L^(-1) NaOH, and 0.20 g·mL^(-1) solid–liquid ratio), the leaching efficiencies of V and Mo reached 94.35% and 96.23%, respectively. It has been confirmed that microwave energy has considerable potential to enhance the efficiency of the leaching process and reduce the leaching time. It is suggested that the enhancement of the leaching efficiencies of V and Mo can be attributed to the existence of a thermal gradient between solid and liquid and the generation of cracks on the mineral surface.

关键词： microwave spent petrochemical catalyst vanadium molybdenum

Ab initio study of the reaction path of the reaction HNCO+CN

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Science China Chemistry 2005年第4期48卷 279-285页

作者： ZHANG Xinzhuang zhen zhen liu Xinhou Technical Institute of Physics and Chemistry of Chinese Academy of Sciences Beijing 100101China Technical Institute of Physics and Chemistry of Chinese Academy of SciencesBeijing 100101China Technical Institute of Physics and Chemistry of Chinese Academy of SciencesBeijing 100101China

We report ab initio UMP2 calculations of the reaction of CN with HNCO using 6-311G(d,p) basis *** obtained results show that the reaction has two product channels:HNCO+CN→HCN+NCO (1) and HNCO+CN→HNCN+CO (2).Channel (1) is a hydrogen abstraction reaction,which is a concerted *** calculated potential energy barrier is 20.80 kJ/mol at UMP2(full)/6-311G(d,p) *** the range of reaction temperature (1000―2100 K),the conventional transition theory rate constant for channel (1) ranges from 0.32×10?11 to 6.9×10?11cm3?mol?1·s?1,which is close to the experimental *** (2) is a stepwise re-action involving an intermediate during the process of *** UMP2(full)/6-311G(d,p) po-tential energy barrier is 83.42 kJ/mol for the rate-controlling step,which is much higher than that of channel (1).

关键词： isocyanic acid, radical reaction, ab initio method, intermediate.

New Upper Bounds on Linear Coloring of Planar Graphs

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Acta Mathematica Sinica,English Series 2012年第6期28卷 1187-1196页

作者： Bin liu Gui zhen liu Department of Mathematics Ocean University of China School of Mathematics Shandong University

A proper vertex coloring of a graph G is linear if the graph induced by the vertices of any two color classes is the union of vertex-disjoint paths. The linear chromatic number lc（G） of the graph G is the smallest number of colors in a linear coloring of G. In this paper, it is proved that every planar graph G with girth g and maximum degree A has （1） lc（G） ≤ △ ＋ 21 if △ ≥ 9; （2） lc（G） ≤[△/2]＋ 7 if g≥5; （3） lc（G） ≤ [△/2]＋2ifg≥7and△ ≥7.

关键词： Linear coloring planar graph girth

Poisson Stable Solutions for Stochastic Differential Equations with Lévy Noise

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Acta Mathematica Sinica,English Series 2022年第1期38卷 22-54页

作者： Xin liu zhen Xin LI School of Mathematical Sciences Dalian University of TechnologyDalian 116024P.R.China

In this paper,we use a unified framework to study Poisson stable(including stationary,periodic,quasi-periodic,almost periodic,almost automorphic,Birkhoff recurrent,almost recurrent in the sense of Bebutov,Levitan almost periodic,pseudo-periodic,pseudo-recurrent and Poisson stable)solutions for semilinear stochastic differential equations driven by infinite dimensional L′evy noise with large *** suitable conditions on drift,diffusion and jump coefficients,we prove that there exist solutions which inherit the Poisson stability of *** we show that these solutions are globally asymptotically stable in square-mean ***,we illustrate our theoretical results by several examples.

关键词： Stochastic differential equation Lévy noise periodic solution quasi-periodic solution almost periodic solution Levitan almost periodic solution almost automorphic solution Birkhoff recurrent solution Poisson stable solution asymptotic stability

Dynamic Response Study of Steel Catenary Riser Based on Slender Rod Model

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China Ocean Engineering 2019年第1期33卷 57-64页

作者： liu zhen GUO Hai-yan College of Engineering Ocean University of China

A numerical model of the steel catenary riser(SCR) is built based on the slender rod model. The slender rod model,which describes the behavior of the slender riser in terms of the center line position, can solve the geometrical nonlinearity effectively. In a marine environment, the SCR is under the combined internal flow and external loads,such as wave and current. A general analysis considers only the inertial force and the drag force caused by the wave and current. However, the internal flow has an effect on the SCR; it is essential to explore the dynamic response of the SCR with the internal flow. The SCR also suffers the lift force and the fluctuating drag force because of the current. Finite element method is utilized to solve the motion equations. The effects of the internal flow, wave and current on the dynamic response of the SCR are considered. The results indicate that the increase of the internal flow density leads to the decrease of the displacement of the SCR, while the internal flow velocity has little effect on the SCR. The displacement of the SCR increases with the increase of the wave height and period. And the increasing wave period results in an increase in the vibration period of the SCR. The current velocity changes the displacements of the SCR in x-and z-directions. The vibration frequency of the SCR in y-direction increases with the increase of the current velocity.

关键词： steel catenary riser slender rod model internal flow dynamic response