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NONOSCILLATORY COMBINATION OF MAC CORMACK AND WARMING-BEAM SCHEMES FOR HYPERBOLIC CONSERVA-TION LAWS

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Journal of Hydrodynamics 2000年第2期12卷 101-106页

作者： Yu, Heng liu, Yuping Fudan Univ Shanghai China

Based on the analysis of nonoscillatory conditions of second-order schemes, a very simple combination of the two famous second-order finite difference schemes, the Mac Cormack scheme and the Warming-Beam scheme, was achieved for hyperbolic conservation laws. It can avoid spurious oscillations near discontinuities and preserve uniformly second order accuracy in space and time. Numerical results show lower cost and even better resolution than ENO schemes under same conditions.

关键词： Finite difference method Nonlinear systems Oscillations

Comparison between the Seismic Performance of Buried Pipes and Pipes in a Utility Tunnel

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Computer Modeling in Engineering & Sciences 2020年第5期123卷 661-690页

作者： Wei liu Qianxiang Wu State Key Laboratory of Disaster Reduction in Civil Engineering Tongji UniversityShanghai200092China Department of Structural Engineering Tongji UniversityShanghai200092China

A utility tunnel system consists of pipes and ancillary *** this paper,a finite element model of a concrete utility tunnel with pipes inside is *** tunnel segments were built to simulate a real utility tunnel,while the pipe was fixed by springs on the brackets in the utility *** the discrete soil spring element to simulate the soil-structure interaction,actual earthquake records were adopted as excitation to analyze the seismic responses of pipes in a utility ***,the influences of different parameters,including soil type,earthquake records,and field apparent wave velocity on the seismic responses of the utility tunnel and the pipes inside were ***,the seismic responses of buried pipes were analyzed and compared with those of pipes in a utility tunnel to evaluate the seismic performance of pipes for two working conditions.

关键词： Pipe in utility tunnel buried pipe seismic performance

Basic mathematical model for the normal black smoker system and the hydrothermal megaplume formation

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Acta Oceanologica Sinica 2007年第6期26卷 30-40页

作者： liu Longlong ZHAI Shikui College of Marine Geoscience Ocean University of China Qingdao 266003 China

A tube model to simulate the normal black smoker system has been built, where the Darcy flow equation, the Ergun equation and the turbulent pipe flow equation are used respectively to describe the dynamic process of different key areas in the hydrothermal circulation system. At the same time, a convection - diffuse Equation for the temperature field is used for describe the exchange of thermal energy and the law of temperature variation. Combining the above facts and using efficient mathematical algorithms and programming with the MatLab programming language, the variation curves of temperature, pressure and mass flow rate are determined, while also the dynamic heat equilibrium and pressure equilibrium within the black smoker system are analyzed. On the basis of the model of the normal black smoker system, a megaplume formation model is further built. For instance, the hydrothermal venting plume on the Juan de Fuca Ridge has been simulated and the simulation results are fairly consistent with Baker＇ s imputed data in 1986. On the basis of the above productive simulation, a series of factors for megaplume formation and the effectiveness of the main parameters of the periodicity of the megaplume formation, temperature and the maximum mass flow rate are systematically discussed. Main conclusions are as follows： The normal black smoker system can evolve into a megaplum eruption. In fact, the passageway of the hydrothermal discharge is blocked by the hydrothermal sediments during the black smoker period, which leads to a hydrothermal fluid accumulation, rise of temperature and increase of buoyancy pressure under the seabed. After a period of 2 - 3 a, the megaplume hydrothermal eruption will occur when the increasing buoyancy pressure is high enough to crack the blockage （cap）. Meanwhile, the temperature of the heat source must exceed 500 ℃, while the highest temperature of the eruption fluid may be high up to 413 ℃, which is fairly consistent with the surveying data. If

关键词： normal black smoker megaplume mathematical model simulation for hydrothermal circulation system

Stable Fatigue Crack Propagation of 16MnR Steel

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Journal of Beijing Institute of Technology 2020年第4期29卷 603-612页

作者： Yanwen liu Guangyuan Jin Jinjun Gao Yajie liu School of Mechatronics Engineering Harbin Institute of TechnologyHarbin 150001China Heilongjiang Institute of Industrial Technology Harbin 150001China

A research on the stable fatigue crack propagation of 16MnR steel is investigated systematically in this ***,control experiments of 16MnR with compact tension specimen is conducted to study the effect of R-ratios,specimen thickness and notch *** experiments show that the fatigue crack growth(FCG)rate in stable propagation was insensitive to these ***,the stress intensity factor(SIF)is computed and compared by displacement interpolation method,J integral and interaction integral method *** simulation shows that optimization on the mesh density and the angle of singular element improved the computational efficiency and accuracy of SIF and the interaction integral method has an obvious advantage on ***,the FCG rate is modeled by the Jiang fatigue damage criterion and the extended finite element method(XFEM)*** simulation results of FCG rate are in line with experiments data and indicate that XFEM method is more accurate than Jiang fatigue damage method.

关键词： 16MnR crack propagation stress intensity factors fatigue damage extended finite element method

Fuzzy finite element model updating of bridges by considering the uncertainty of the measured modal parameters

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Science China(Technological Sciences) 2012年第11期55卷 3109-3117页

作者： liu Yang DUAN ZhongDong School of Transportatton Science and Engineering Harbin Institute of TechnologyHarbin 150090China Harbin Institute of Technology Shenzhen Graduate School Shenzhen 5180553China

It is significant to consider the effect of uncertainty of the measured modal parameters on the updated finite element(FE) model,especially for updating the FE model of practical bridges,since the uncertainty of the measured modal parameters cannot be ignored owing to the application of output-only identification method and the existence of the measured noise.A reasonable method is to define the objective of the FE model updating as the statistical property of the measured modal parameters obtained by conducting couples of identical modal tests,however,it is usually impossible to implement repeated modal test due to the limit of practical situation and economic *** this study,a method based on fuzzy finite element(FFM) was proposed in order to consider the effect of the uncertainty of the measured modal parameters on the updated FE model by using the results of a single modal *** updating parameters of bridges were deemed as fuzzy variables,and then the fuzzification of objective of the FE model updating was proposed to consider the uncertainty of the measured modal ***,the effectiveness of the proposed method was verified by updating the FE model of a practical bridge with the measured modal parameters.

关键词： bridge finite element model updating fuzzy finite element interval analysis fuzzy theory

A three-dimensional solid-liquid two-phase turbulence model with the effect of vegetation in non-orthogonal curvilinear coordinates

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Science China(Physics,Mechanics & Astronomy) 2009年第7期52卷 1062-1073页

作者： liu Cheng SHEN YongMing Coastal&Estuary Dynamics Section Pearl River Hydraulic Research InstituteGuangzhou 510611China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116023China

A three-dimensional k-ε-Ap solid-liquid two-phase two-fluid model with the effect of vegetation is solved numerically with a finite-volume method on an adaptive grid to study water-sediment movements and bed evolution in vegetated channels. The additional drag force and additional turbulence generation due to vegetation are added to the relevant control equations for simulating the interaction between vegetation and flow. The flow structure and the bed-topography changes in a 60° partly vegetated channel bend are calculated by the model. The numerical results agree well with the measured ones. Calculated and measured results show that the primary flow velocity reduces much in the vegetation zone and increases in the non-vegetation zone, the secondary flow velocity weakens in the vegetation zone and strengthens in the non-vegetation zone, the sediment movement and bed-topography change also weaken in the vegetation zone and strengthen in the non-vegetation zone, a well-planed vegetation arrangement can improve bank stabilization program, and the k-ε-Ap model can deal with bed-load transport with a more reasonable method than the one-fluid model.

关键词： adaptive grid three dimensional k-ε-A_(p)model solid-liquid two-phase turbulence model vegetation channel bend sediment transport bed-topography change

SLIDING MODE CONTROL FOR ACTIVE AUTOMOBILE SUSPENSIONS

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Chinese Journal of Mechanical Engineering 1998年第1期11卷 12-19页

作者： Zhang, Jianwu liu, Xinliang Shanghai Jiaotong Univ Shanghai China

Nonlinear control methods are presented based on theory of sliding mode control (SMC) or variable structure control (VSC) for application to active automobile suspensions. Requirements of reducing manufacturing cost and energy consumption of the active suspension system may be satisfied by reasonable design of the sliding surface and hydraulic servo system. Emphasis is placed on the study of the discrete sliding mode control method (DSMC) applicable for a new sort of speed on off solenoid valves of anti dust capability and low price. Robustness and effectiveness of the feedback linearized controller in typical road conditions are demonstrated by numerical results for a quarter car suspension model.

关键词： Automobile suspension Siding mode control Nonlinear dynamics

On Non-commuting Sets in Certain Finite p-Groups

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Algebra Colloquium 2015年第4期22卷 555-560页

作者： Heguo liu Yulei Wang Department of Mathematics Hubei University Wuhan 430062 China vDepartment of Mathematics Henan University of Technology Zhengzhou 450001 China

Let G be a group. A subset X of G is said to be non-commuting if xy ≠ yx for any x, y ∈ X with x ≠ y. If {X}≥ IYI for any other non-commuting set Y in G, then X is said to be a maximal non-commuting set. In this paper, the bound for the cardinality of a maximal non-commuting set in a finite p-group G is determined, where G is a non-abelian p-group given by a central extension as1 → Zp→ G →Zp ×→ × Zp →1 and its derivedsubgroup has order p.

关键词： generalized extraspecial p-group central product non-commuting set

Calibration of digital camera integration accuracy for low-cost oblique aerial photogrammetry

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Geo-Spatial Information Science 2015年第2期18卷 90-96页

作者： Likun liu Zhenfeng SHAO China Ship Development and Design Center 268 Zhangzhidong RoadWuhan 430064China State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan University129 Luoyu RoadWuhan 430079China Collaborative Innovation Center for Geospatial Technology 129 Luoyu RoadWuhan 430079China

This work describes a calibration process for inexpensive consumer cameras integrated into a low cost and compact aerial multi-view imager for remote sensing and *** main advantage of this design is to make the filming component lightweight and rapidly deployable,as well as reducing cost when compared with mainstream commercial oblique *** in situ flight test was carried out in *** that experiment,a meridian convergence-based approach was adopted to adjust preprocessing,the residue error and the captured images’exterior orientation linear and angular parameters were calculated by means of the direct geo-referencing approach yielding a favorable outcome for exterior orientation linear parameters of the camera,around 0.2–0.3 m deviation from the actual measured results at 1000 m flight above ground *** camera’s exterior orientation angular parametersφ,ωwhose difference compared with the standard aerial aero triangulation approach reached a high accuracy level within the intended endurance of 0.005°.These results indicate that the compact implementation of the oblique aerial imager comprised of consumer level off-the-shelf digital cameras achieved competitive accuracy at a low cost and high versatility.

关键词： oblique photogrammetry aerial imager calibration digital camera position and orientation