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Numerical analysis of nonlinear dynamic behavior of earth dams

Babak EBRAHIMIAN

《结构与土木工程前沿（英文）》 2011年第5卷第1期页码 24-40 doi: 10.1007/s11709-010-0082-6

摘要： A numerical study is conducted to investigate the dynamic behavior of earth dams. The numerical investigation employs a fully nonlinear dynamic finite difference analysis incorporating a simple elastic perfectly plastic constitutive model to describe the stress-strain response of the soil and the Rayleigh damping to increase the level of hysteretic damping. The extended Masing rules are implemented into the constitutive model to explain more accurately the soil response under general cyclic loading. The soil stiffness and hysteretic damping change with loading history. The procedures for calibrating the constructed numerical model with centrifuge test data and also a real case history are explained. For the latter, the Long Valley (LV) earth dam subjected to the 1980 Mammoth Lake earthquake as a real case-history is analyzed and the obtained numerical results are compared with the real measurements at the site in both the time and frequency domains. Relatively good agreement is observed between computed and measured quantities. It seems that the Masing rules combined with a simple elasto-plastic model gives reasonable numerical predictions. Afterwards, a comprehensive parametric study is carried out to identify the effects of dam height, input motion characteristics, soil behavior, strength of the shell materials and dam reservoir condition on the dynamic response of earth dams. Three real earthquake records with different levels and peak acceleration values (PGAs) are used as input motions. The results show that the crest acceleration decreases when the dam height increases and no amplification is observed. Further, more inelastic behavior and more earthquake energy absorption are observed in higher dams.

关键词： earth dam numerical nonlinear response dynamic analysis earthquake dam height

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Dynamic behavior of superheated steam and ways of control

LI Xu

《能源前沿（英文）》 2008年第2卷第1期页码 25-30 doi: 10.1007/s11708-008-0014-5

摘要： A simple way of calculating the dynamic behavior of a superheater is presented. A comparison of the measured data with the calculated result verifies the accuracy of this simple method. It is the first time that a phase compensation for real roots, i.e., the twin lead/lag loop which is facile for engineering applications, is used in superheated steam temperature control. Numerous simulation results show that both the response time lapse and maximal dynamic deviation are greatly reduced. Moreover, a formula to calculate the setting parameters is presented, together with a practical example of its engineering application in superheated steam temperature control with single-stage attemperation in a power plant boiler. This method can remarkably improve the control performance of superheated steam temperature and makes it possible for one stage attemperation to be sufficient for the superheater of power plant boilers, thus simplifying the superheater system and reducing investment. Because the control performance is remarkably raised, the set values of the steam temperature control system can be raised above rated values and also the operational economy, without impairing the operation safety.

关键词： engineering investment Numerous simulation lead/lag temperature

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Numerical studies of dynamic behavior of liquid film on single-layer wire mesh with different wettabilities

《化学科学与工程前沿（英文）》页码 1672-1680 doi: 10.1007/s11705-022-2205-8

摘要： Droplet impacting on the stainless steel wire mesh is very common in chemical devices, like a rotating packed bed. Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance. However, the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown. In this work, the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation. The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps: (1) spreading step; (2) shrinkage process; (3) stabilizing or disappearing step. Effects of surface wettability, as well as operating conditions, on wetting area and liquid film thickness were studied. Compared to the hydrophilic wire mesh, the final wetting area of hydrophobic wire mesh is zero in most cases. The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29 μm, and that of hydrophobic wire mesh is 41.76–237.37 μm. This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities, which can be guiding the packing optimization and design.

关键词： stainless steel wire mesh computational fluid dynamics surface wettability liquid film impacting

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Nonlinear dynamic behavior of rotating blade with breathing crack

Laihao YANG, Zhu MAO, Shuming WU, Xuefeng CHEN, Ruqiang YAN

《机械工程前沿（英文）》 2021年第16卷第1期页码 196-220 doi: 10.1007/s11465-020-0609-z

摘要： This study aims at investigating the nonlinear dynamic behavior of rotating blade with transverse crack. A novel nonlinear rotating cracked blade model (NRCBM), which contains the spinning softening, centrifugal stiffening, Coriolis force, and crack closing effects, is developed based on continuous beam theory and strain energy release rate method. The rotating blade is considered as a cantilever beam fixed on the rigid hub with high rotating speed, and the crack is deemed to be open and close continuously in a trigonometric function way with the blade vibration. It is verified by the comparison with a finite element-based contact crack model and bilinear model that the proposed NRCBM can well capture the dynamic characteristics of the rotating blade with breathing crack. The dynamic behavior of rotating cracked blade is then investigated with NRCBM, and the nonlinear damage indicator (NDI) is introduced to characterize the nonlinearity caused by blade crack. The results show that NDI is a distinguishable indicator for the severity level estimation of the crack in rotating blade. It is found that severe crack (i.e., a closer crack position to blade root as well as larger crack depth) is expected to heavily reduce the stiffness of rotating blade and apparently result in a lower resonant frequency. Meanwhile, the super-harmonic resonances are verified to be distinguishable indicators for diagnosing the crack existence, and the third-order super-harmonic resonances can serve as an indicator for the presence of severe crack since it only distinctly appears when the crack is severe.

关键词： rotating blade breathing crack nonlinear vibration nonlinear damage indicator

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Measurement of dynamic fracture toughness and failure behavior for explosive mock materials

Pengwan CHEN, Zhongbin ZHOU, Shaopeng MA, Qinwei MA, Fenglei HUANG

《机械工程前沿（英文）》 2011年第6卷第3期页码 292-295 doi: 10.1007/s11465-011-0237-8

摘要：

In this work, a pre-cracked semi-circular shaped explosive simulant was loaded using a split Hopkinson pressure bar (SHPB). A high-speed camera was used to capture the deformation and fracture process of the specimen in situ. The digital images were processed using the digital image correlation (DIC) method. Next, full displacement and strain fields were obtained. The displacement vector field shows that the specimen fractured under tensile stress action. The strain field can be used to predict the crack propagation. Results show that the method of combined DIC and SHPB is effective to study the dynamic deformation and fracture behavior of explosive simulants. In addition, the specimen was loaded using a drop weight. The fracture toughness of the specimen was preliminary measured.

关键词： digital image correlation polymer bonded explosive simulant split Hopkinson pressure bar (SHPB) semicircular bending test deformation fracture toughness

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Centrifuge model test on dynamic behavior of group-pile foundation with inclined piles and its numerical

ZHANG Feng, OKAWA Katsunori, KIMURA Makoto

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 233-241 doi: 10.1007/s11709-008-0033-7

摘要： In this paper, dynamic behavior of a group-pile foundation with inclined piles in loose sand has been investigated with centrifuge model tests. The test results are also simulated with elastoplastic dynamic finite element method, in which, not only sectional force of piles, stress of ground, but also deformation of piles are calculated using a three-dimensional elastoplastic dynamic finite element analysis (Code name: DGPILE-3D). The numerical analyses are conducted with a full system in which a superstructure, a pile foundation and surrounding ground are considered together so that interaction between pile foundation and soils can be properly simulated because the nonlinearities of both the pile and the ground are described with suitable constitutive models. Different types of piles, vertical pile or inclined pile, are considered in order to verify the different characteristics of a group pile foundation with inclined piles. The validity of the calculation is verified by the model tests.

关键词： centrifuge Different three-dimensional elastoplastic calculation inclined

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Molecular size characterization of heavy oil fractions in vacuum and solution by molecular dynamic simulation

Wenpo REN, Honggang CHEN, Chaohe YANG, Honghong SHAN,

《化学科学与工程前沿（英文）》 2010年第4卷第3期页码 250-256 doi: 10.1007/s11705-009-0281-7

摘要： Two kinds of heavy oils were fractionated into eight fractions by Liquid-Solid Adsorption Chromatography, respectively, and samples were collected to measure properties. According to the elemental analysis, molecular weight and H-NMR data, average molecular structures of polycyclic aromatic and heavy resin were constructed with improved Brown-Ladner (B-L) method and several corrections. And then, the most stable conformations of polycyclic aromatic and heavy resin in vacuum and toluene solution were obtained by molecular dynamic simulation, and the molecular size was gotten via the radius of gyration analysis. The results showed that the radius of gyration of polycyclic aromatic and heavy resin was 0.55–0.70 nm in vacuum and 0.60–0.90 nm in toluene solution. With molecular weight increasing, the molecular size in vacuum and toluene solution also increased. Due to the swelling behavior of solvent, the alkyl side chains of heavy oil molecule in solution were more stretched. Thus, the molecular size in toluene solution was larger than that in vacuum.

关键词： dynamic simulation molecular dynamic behavior molecule Adsorption Chromatography

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Stability and coupling dynamic behavior of nonlinear journal active electromagnetic bearing rotor system

LU Yanjun, HEI Di, WANG Yuan, DAI Rong, LU Yanjun, LIU Heng, YU Lie

《机械工程前沿（英文）》 2008年第3卷第2期页码 193-199 doi: 10.1007/s11465-008-0023-4

摘要： The stability and coupling dynamic behavior of a journal active electromagnetic bearing rotor system are analyzed. The gyroscopic effect is considered in the rotor model. The system equations are formulated by combining equations for rotor motion and decentralized proportional integral differential (PID) controllers. A method combining the predictor-corrector mechanism and the Netwon-Raphson method is presented to calculate the critical speed at the corresponding Hopf bifurcation point of the system. For periodic motions, a continuation method combining the predictor-corrector mechanism and shooting method is presented. Nonlinear unbalanced periodic motions and their stability margins are obtained using the shooting method and established continuation method for periodic motions. With the change of control parameters, the system local stability and bifurcation behaviors are obtained using the Floquet theory. The numerical examples show that the schemes not only significantly save computing cost, but also have high precision.

关键词： proportional integral bifurcation corresponding integral differential predictor-corrector mechanism

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Effects of elastic support on the dynamic behaviors of the wind turbine drive train

Shuaishuai WANG, Caichao ZHU, Chaosheng SONG, Huali HAN

《机械工程前沿（英文）》 2017年第12卷第3期页码 348-356 doi: 10.1007/s11465-017-0420-7

摘要：

The reliability and service life of wind turbines are influenced by the complex loading applied on the hub, especially amidst a poor external wind environment. A three-point elastic support, which includes the main bearing and two torque arms, was considered in this study. Based on the flexibilities of the planet carrier and the housing, a coupled dynamic model was developed for a wind turbine drive train. Then, the dynamic behaviors of the drive train for different elastic support parameters were computed and analyzed. Frequency response functions were used to examine how different elastic support parameters influence the dynamic behaviors of the drive train. Results showed that the elastic support parameters considerably influenced the dynamic behaviors of the wind turbine drive train. A large support stiffness of the torque arms decreased the dynamic response of the planet carrier and the main bearing, whereas a large support stiffness of the main bearing decreased the dynamic response of planet carrier while increasing that of the main bearing. The findings of this study provide the foundation for optimizing the elastic support stiffness of the wind turbine drive train.

关键词： wind turbine drive train elastic support dynamic behavior frequency response function

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Analysis of behavior of melted dark green silty soil

TANG Yiqun, ZHOU Nianqing, YANG Ping, SHEN Feng

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 242-245 doi: 10.1007/s11709-008-0022-x

摘要： The behavior of dark green silty soil of the 6th storey is studied by means of scanning electron microscopy (SEM). The shape, size and contact condition of the basic elements of the soil microstructure, and the shape and the size of the pore are further studied. In addition, a comparative study is made to analyze the experiment results of Cu and dynamic test. The mechanic characteristics of common soil and those of melted soil are presented and their influences on dark silty soil after being frozen are theoretically illustrated from a microscopic perspective.

关键词： electron microscopy mechanic microscopic perspective addition dynamic

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Simplified theoretical analysis and numerical study on the dynamic behavior of FCP under blast loads

Chunfeng ZHAO, Xin YE, Avinash GAUTAM, Xin LU, Y. L. MO

《结构与土木工程前沿（英文）》 2020年第14卷第4期页码 983-997 doi: 10.1007/s11709-020-0633-4

摘要： Precast concrete structures have developed rapidly in the last decades due to the advantages of better quality, non-pollution and fast construction with respect to conventional cast-in-place structures. In the present study, a theoretical model and nonlinear 3D model are developed and established to assess the dynamic behavior of precast concrete slabs under blast load. At first, the 3D model is validated by an experiment performed by other researchers. The verified model is adopted to investigate the blast performance of fabricated concrete panels (FCPs) in terms of parameters of the explosive charge, panel thickness, and reinforcement ratio. Finally, a simplified theoretical model of the FCP under blast load is developed to predict the maximum deflection. It is indicated that the theoretical model can precisely predict the maximum displacement of FCP under blast loads. The results show that the failure modes of the panels varied from bending failure to shear failure with the mass of TNT increasing. The thickness of the panel, reinforcement ratio, and explosive charges have significant effects on the anti-blast capacity of the FCPs.

关键词： precast structure fabricated concrete panel blast resistance theory model empirical equation

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恶意代码行为描述与分析综述 Review

Bo YU, Ying FANG, Qiang YANG, Yong TANG, Liu LIU

《信息与电子工程前沿（英文）》 2018年第19卷第5期页码 583-603 doi: 10.1631/FITEE.1601745

摘要：基于行为的分析是恶意代码自动分析和检测过程中的一项重要技术，近年来得到学术界和工业界极大关注。恶意代码行为分析技术，能够避免传统静态分析技术遇到的恶意代码混淆的障碍，也能够通过行为描述规范表达恶意代码样本多样化的行为类型。目前，虽有一些关注恶意代码行为分析的工作，但基于行为的恶意代码分析技术仍未成熟，目前尚未发现介绍当前研究进展和发展挑战的综述。本文从3个方面对恶意代码的行为描述和分析进行综述：恶意代码行为描述，恶意代码行为分析模型，可视化。首先，全面梳理了现有行为分析技术的分析目标、原则、特点和分类，包括现有行为数据类型和描述方法；其次，从多方面分析恶意代码分析的不足和挑战；最后，探讨了潜在研究热点。

关键词：恶意代码行为；静态分析；动态分析；行为数据表示；行为分析；机器学习；基于语义的分析；行为可视化；恶意代码演化

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Large deflection behavior effect in reinforced concrete columns exposed to extreme dynamic loads

Masoud ABEDINI, Azrul A. MUTALIB, Chunwei ZHANG, Javad MEHRMASHHADI, Sudharshan Naidu RAMAN, Roozbeh ALIPOUR, Tohid MOMENI, Mohamed H. MUSSA

《结构与土木工程前沿（英文）》 2020年第14卷第2期页码 532-553 doi: 10.1007/s11709-020-0604-9

摘要： Reinforced concretes (RC) have been widely used in constructions. In construction, one of the critical elements carrying a high percentage of the weight is columns which were not used to design to absorb large dynamic load like surface bursts. This study focuses on investigating blast load parameters to design of RC columns to withstand blast detonation. The numerical model is based on finite element analysis using LS-DYNA. Numerical results are validated against blast field tests available in the literature. Couples of simulations are performed with changing blast parameters to study effects of various scaled distances on the nonlinear behavior of RC columns. According to simulation results, the scaled distance has a substantial influence on the blast response of RC columns. With lower scaled distance, higher peak pressure and larger pressure impulse are applied on the RC column. Eventually, keeping the scaled distance unchanged, increasing the charge weight or shorter standoff distance cause more damage to the RC column. Intensive studies are carried out to investigate the effects of scaled distance and charge weight on the damage degree and residual axial load carrying capacity of RC columns with various column width, longitudinal reinforcement ratio and concrete strength. Results of this research will be used to assessment the effect of an explosion on the dynamic behavior of RC columns.

关键词： RC column scaled distance blast load LS-DYNA

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Dynamic behavior of stormwater quality parameters in South Texas

Xubin PAN, Jingyi ZHANG, Wei-Ta FANG, Kim D. JONES

《环境科学与工程前沿（英文）》 2012年第6卷第6期页码 825-830 doi: 10.1007/s11783-012-0465-0

摘要： To control water impairment in urban stormwater, it is important to evaluate changing patterns of water quality parameters in stormwater runoff. Thus, the authors performed a series of experiments to investigate the dynamics of common water parameters during storm events in semi-arid areas, with multiple samples collected and analyzed in field stormwater applications. At this field monitoring site within McAuliffe Park, McAllen, Texas, in the United States, a storm event increased the concentrations of ( ), but this event represented a decreasing trend over the entire event period. Besides, peak intensity of different pollutants in the stormwater runoff occurred at different times other than at any peak flows, representing a complexity of the temporal and spatial measurements. Multi-sample per-event approaches recommended based on the complexity of the hydrograph and different peak intensity times of pollutants. In addition, high bacteria and total suspended solids (TSS) concentrations in the initial stage of the storm event should be considered when designing Best Management Practices (BMPs) and Low Impact Developments (LIDs). New strategies and solutions for addressing ecohydrological challenges should be proposed to avoid collateral damages to their both common wealth in ecosystems and human well-beings.

关键词： event mean concentration first flush multi-sample per event ecohydrology

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三塔双跨悬索桥动力特性分析

阮静,马如进

《中国工程科学》 2010年第12卷第8期页码 83-87

摘要：

桥梁结构的动力特性对进行桥梁的动力性能设计、健康检测和维护具有十分重要的意义，而三塔双跨悬索桥具有和传统的大跨径悬桥不完全相同的静、动力性能。针对泰州大桥工程实例，通过ANSYS有限元分析软件研究了三塔双跨悬索桥在成桥阶段和施工阶段的动力特性，并与传统的悬索桥作比较，得出了一些有意义的结论，供工程设计人员参考。

关键词：三塔双跨悬索桥动力特性自振频率振型