有源电力滤波器空间矢量滞环控制的研究

针对因非线性负载引起的电网谐波污染问题,引入有源电力滤波器(Active power filter,APF)进行治理.分析滞环比较法的工作过程并指出不足,引入空间矢量法解决输出电压相间干扰问题.改进APF的控制策略,把滞环比较和空间矢量结合起来实现电流跟踪控制.最后通过MATLAB/Simulink仿真,比较两种控制策...     

ANN approach to sorption hysteresis within a coupled hygro‐thermo‐mechanical FE analysis

Non‐linear deformable porous media with sorption (capillary condensation) hysteresis are considered. An artificial neural network with two hidden layers is trained to interpolate the sorption hysteresis using a set of experimental data. The performance of the ANN, which is applied as a procedure in the FE code, is investigated, both from numerical, as well as from physical viewpoint. The ANN‐FE code has been developed and tested for 1‐D and 2‐D problems concerning cyclic wetting–drying of concrete elements. In general, the application of the ANN procedure inside the classical FE program does not have any negative effect on the numerical performance of the code. The results obtained indicate that the sorption isotherm hysteresis is of importance during analysis of hygrothermal and mechanical behaviour of capillary‐porous materials. The most distinct differences are observed for the saturation and displacement solutions. The ANN‐FE approach seems to be an efficient way to take into account the influence of hysteresis during analysis of hygro‐thermal behaviour of capillary‐porous materials. Copyright © 2001 John Wiley & Sons, Ltd.     

基于Karnopp摩擦模型的比例阀颤振响应研究

颤振有助于改善比例阀响应特性,其频率及幅度参数与比例阀结构参数直接相关。基于开环比例控制阀仿真模型,研究功率级阀芯的颤振响应、颤振信号降低摩擦滞环的机制并确定最优参数范围。建立仿真模型,颤振信号通过双占空比高频PWM形式引入,基于电磁场有限元方法构建比例电磁铁,采用Karnopp摩擦模型建立衔铁及功率级阀芯动力学方程。仿真结果表明:摩擦模型能够较好地表征电磁铁力滞环及阀芯流量滞环现象;在颤振信号激励下,阀芯产生颤振运动,摩擦力状态在静摩擦与动摩擦间切换,进而影响其响应特性;颤振频率和幅度参数存在最优区间,且由比例阀的结构参数决定。     

Oil palm wood flour filled natural rubber composites: fatigue and hysteresis behaviour

The fatigue and hysteresis behaviour of oil palm wood flour (OPWF) filled natural rubber composites was studied. The stress at any strain decreased with increasing OPWF loading in the composites. As the filler loading increased, the poor wetting of the OPWF by the rubber matrix gave rise to poor interfacial adhesion between the filler and rubber matrix. Results also indicate that the composite with the highest loading of OPWF was the most sensitive towards changes in strain energy, and hence exhibited the highest hysteresis. Thermal ageing not only reduced the fatigue life, but also increased the hysteresis of the composites. © 2000 Society of Chemical Industry     

Damage tracking and hysteresis-based evaluation of seismic-excited RC shear wall using monitoring data

Reinforced concrete (RC) shear walls play an important role as the seismic resisting system in tall buildings. Yet, assessing the seismic damage of real-world shear walls remains a challenging task. In this study, a damage index that relies on the vibration data measured by the sensors embedded in the structure is proposed to evaluate the damage condition of shear walls. The damage index is formed by the linear combination of two normalized terms, which, respectively, characterize the peak and the cumulative damages of the shear walls with little knowledge of real-life structural hysteresis. The damage tracking and evaluation based on the substructure level and the story level are discussed. The damage indices evaluated using the hysteretic loops made by the shear and bending information of the shear wall are further compared. The feasibility of the proposed damage index is examined using a numerically simulated 12-story coupled shear wall structure. It is then applied to analyze the experiments regarding the damage condition of RC shear walls under earthquakes. Results show that the proposed damage index can track the damage states of RC shear walls under seismic excitations. Analysis suggests that the proposed damage index could trace and distinguish the progression of shear and flexural damages, which potentially supports the post-earthquake structural safety management.     

水侵气藏型储气库注采相渗滞后数值模拟修正方法

以天然岩心气水多周期互驱相渗测定实验为基础,揭示了储气库多周期注采相渗滞后效应,结合Carlson和Killough经典相渗滞后理论,建立了水侵气藏型储气库多周期注采相渗滞后数值模拟修正方法,并通过建立的中低渗透砂岩水侵气藏型储气库地质模型,系统研究了多周期注采相渗滞后效应对储气库流体宏观分布规律和生产运行指标的影响....     

全通道有效磁流变阻尼器的性能测试与滞回模型

传统剪切阀式磁流变阻尼器在活塞上缠绕励磁线圈,导致1/2以上长度阻尼通道无效,影响阻尼器的最大出力。为了克服上述缺陷,在前期概念设计和理论分析的基础上,制作了2个全通道有效的磁流变阻尼器模型,测试了其在不同电流输入状态下阻尼通道处的磁场分布以及力-位移、力-速度等力学性能曲线,并通过对改进型Sigmoid模型的参数识别建立了模型阻尼器的动力滞回模型。研究表明,模型阻尼器阻尼通道处的磁场分布与有限元分析结果基本符合,其磁路结构可较好地实现全通道有效;全通道有效磁流变阻尼器的最大阻尼力比传统剪切阀式磁流变阻尼器的最大阻尼力提高一倍以上,阻尼力调节系数提高70%以上;改进型Sigmoid模型结构形式简单,识别精度高,可作为全通道有效磁流变阻尼器的动力滞回模型。     

Locally resolved hysteresis measurement of advanced glass-mat thermoplastic composites

With hysteresis measurement stiffness, creep and damping can be recorded at cyclic loading. Using a laser extensometer a locally resolved hysteresis measurement was formerly developed. It allows to observe several hysteresis-loops simultaneously. Local hysteresis measurement is suitable for fatigue tests of inhomogeneous materials or materials which have inhomogeneous damage process.Locally resolved hysteresis measurement was demonstrated for textile-reinforced advanced glass-mat thermoplastic composites which are interesting for structural components in automotive applications. Cyclic tension tests show stiffness degradation, creep and increasing damping especially for the fracture zones. In cyclic compression loading, the change of the material properties is less pronounced.A component test at a U-profile shows a good agreement between hysteresis measurement and major strain in the fracture zone of the U-profile recorded with digital image correlation.For the interpretation of creep and stiffness degradation at cyclic tension loading, strain oriented considerations were made. It can be shown that for the longitudinal and transversal samples a similar location of the trend-line in a total strain Wöhler-diagram can be found, therefore a total strain dominated failure behavior seems obvious. For further analysis a relative consideration concerning the development of strain amplitude and mid-strain is made. For each single test the ratio between the development of the strain amplitude and the development of the strain middle is calculated. A significant tendency of the above mentioned quotient concerning the stress amplitude can be observed.     

Sorption behavior of tetrabromobisphenol A in two soils with different characteristics

Sorption of tetrabromobisphenol A (TBBPA) in soil influences its fate and transport in the environment. The sorption behaviors of TBBPA in two soils with different characteristics were investigated using batch equilibration experiments in the study, and the impacts of ionic strength and pH on the sorption were also evaluated. The results showed that the fast sorption rather than the slow sorption played a main role in the sorption process. The nonlinear sorption isotherms of TBBPA in the soils were observed and the Freundlich model could describe the sorption behavior of TBBPA well. The calculated K_F were 78.5 and 364.6  (mg/kg)(mg/L)⁻ⁿ for LN soil (loamy clay) and GX soil (silt loam), respectively. Soil organic matter (SOM) played a main role in the sorption of TBBPA, which contributed about 90% to the sorption in the soils. The desorption hysteresis of TBBPA was revealed in the single-cycle sorption and desorption experiments. The sorbed amount of TBBPA decreased with the increase in solution pH and increased with the increase in ionic strength. It was found that the effects of ionic strength on the sorption were mainly caused by the change of solution pH.     

磁流变阻尼器的实验建模

磁流变阻尼器是一种应用前景广阔的半主动控制阻尼器。基于对磁流变阻尼器的实验,建立了描述磁流变阻尼器阻尼特性的Bingham塑性模型和非线性滞回模型。讨论了施加电压（磁场强度）、激振振幅及频率对两种模型的参数的影响。该文提出的非线性滞回模型具有精度高、参数识别过程简单和准确反映磁流变阻尼器滞回特性等优点。