利用MR大数据提升3G用户感知研究

运用大数据挖掘原理,对海量3G终端MR数据进行深入研究。从解决用户感知、用户体验方面入手,寻找网络质量规律,并在优化实例中予以应用。丰富了优化手段,取得良好效果,提高了优化效率,为深度优化提供了新思路。     

某型液压阻尼器启动力差异分析及改进

为解决某型机载液压阻尼器前推与后拉启动力差异较大的问题,对密封结构及阻尼腔排气结构进行改进设计。分析故障机理并确定原因是由密封设置不合理造成的启动力异常以及内部油液未充满造成的伸出方向阻尼性能下降,共同导致了侧杆装置前推后拉启动力差异。验证结果表明：该设计能提高阻尼器的密封性能,满足系统启动力的要求。     

径向流磁流变阀压降性能分析

提出并设计了一种径向流磁流变阀,并加工了样机进行压降性能分析.该径向流磁流变阀的液流通道由2个中心小孔、1个圆环通道和2个径向圆盘通道串联组合而成.采用ANSYS/Emag电磁场仿真软件搭建了径向流磁流变阀有限元仿真模型,并进行了磁场仿真分析以获取理想的仿真压降.搭建了压降性能测试试验台,在不同的加载电流和模拟负载下对所设计的径向流磁流变阀压降性能进行了试验分析.试验压降和仿真压降趋势一致.     

磁流变阻尼器非线性动力学行为的实验研究

磁流变阻尼器具有阻尼力大范围高度可控且耗能功率小的优点,在结构的半主动控制中有广泛的应用。磁流变流体及其元器件的动力学行为因其磁流变现象而存在滞回效应,对这种滞回效应的研究是其相关应用的基础。对磁流变阻尼器在多种激励电流与加载频率下的滞回动力学行为进行了实验研究,并进行了数学建模与参数识别。结果表明:磁流变阻尼器的阻尼力大小由激励电流控制,其非线性滞回特性具有频率依赖性;实验数据与模型仿真值的比较显示,模型可以准确模拟磁流变阻尼器滞回阻尼特性。     

钢连桥人致振动及TMD减振效应实测与分析

以某室外大跨轻柔钢结构人行桥为案例,介绍了该结构的设计概况及调谐质量阻尼器(tuned mass damper,简称TMD)减振设计,分别在结构施工完成后以及TMD装置安装后对其进行了实地动力测试,测得了该结构减振前后的模态特性以及在多种人行荷载工况下的振动响应,采用加速度峰值和均方根值为评价指标,分析了钢连桥人致振动情况及特性。结果表明:一端设计为滑动连接的钢连桥人致振动主要由第1阶竖向振型控制,扭动及水平振动响应相对较小;安装经优化设计的TMD装置后,整体连桥的频率特性没有明显变化,分布式TMD对多种频率激励工况均有良好的调谐减振作用,减振率达到35%~70%;共振激励下测得的原结构阻尼比较小,安装TMD后结构的阻尼比提高4倍,并且呈现出在自由振动衰减的前期较大,随着振动幅度变弱阻尼比降低;测试中发现TMD装置的减振效率对其阻尼比的变化不敏感。     

重卡驾驶室半主动悬置控制方法

为了抑制在路面激励下某型重卡驾驶室的振动加速度响应,研究基于磁流变阻尼器驾驶室半主动悬置系统的控制方法。建立了重卡驾驶室半主动悬置集中质量动力学模型,分别采用比例积分微分(proportion integration differentiation,简称PID)控制理论和模糊最优控制理论设计控制器,并利用磁流变阻尼器动力特性实验数据对模糊最优控制器的参数进行优化。以驾驶室质心垂直、侧倾及俯仰3个方向加速度为控制目标,利用ADAMS/Simulink联合仿真方法,对比分析PID控制和模糊最优两种控制策略与被动状态下重卡驾驶室悬置振动控制效果。针对实际重卡进行不同速度路面激励下的振动控制实验。仿真和实验结果表明,采用PID和模糊最优控制方法均能有效抑制重卡驾驶室半主动悬置的振动加速度响应,其中模糊最优控制效果总体优于PID控制。     

核级密闭型隔离风阀运行过程中仿真力矩计算

以配带肘节式增力机构的核级密闭型隔离风阀为例,利用三维流场和运动仿真模拟隔离风阀叶片运行过程中的流态分布,确定由于流态施加到叶片上的气动力矩,并考虑了叶片运行过程中地震载荷的影响,给出了驱动力矩的计算方法,验证电动装置的选择的正确性。     

Dielectric behavior and magnetical response for porous BFO thin films with various thicknesses over Pt/Ti/SiO2/Si substrate

A novel sol–gel method has been developed to deposit multiferroic nanocrystalline bismuth ferrite (BFO) thin films over Pt/Ti/SiO₂/Si substrate by spin-coating technique with various thicknesses. It is found that the deposition parameters significantly influence the quality and the thickness of BiFeO₃ films. The films are all uniform and adherent to Pt/Ti/SiO₂/Si substrate. The spin-coated films are characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Atomic force microscope (AFM), photoluminescence spectroscopy (PL) and Fourier transform infrared spectroscopy (FTIR). Rhombohedral structure of BFO is confirmed from the XRD and FT-IR studies. The SEM image shows a porous structure formation of BFO over Pt/Ti/SiO₂/Si substrate. The surface outgrowth for the films at various thicknesses is measured from root mean square (RMS) and surface roughness through AFM. The step height and the RMS are found to be high for the film at 500 nm in comparison with thickness of 200 nm. The influence of the dielectric properties of the porous BFO at different thicknesses is studied using LCRQ meter. Finally, the magnetic behavior of film is compared with M–H hysteresis loop and Magnetoresistance (MR) studies.     

Effect of gusset connection configurations on frame–gusset interaction in steel buckling‐restrained braced frame

Although buckling restrained braces (BRBs) are commonly applied in seismic buildings to mitigate structural damage, their performance was often limited by rupture of the corner gusset connections due to additional frame action. This issue may be resolved by alternative gusset connections to mitigate the frame–gusset interaction. In this study, commonly used procedures for design of the traditional gusset connection are reviewed, followed by a case study on the effect of frame action on the structural behavior of these gusset connections in steel frames with BRBs. Inspired by these analysis, two different strategies, aiming at releasing frame–gusset shear interaction using sliding gusset connection or reducing normal interaction using dual gusset plates, are tried to mitigate the frame action effects. Finite element analysis is conducted on steel frame subassemblages with/without BRBs to examine the effect of different gusset connections on the structural behavior of these framing systems. It shows that the sliding gusset connection shows beneficial effect in reducing the frame action, having much smaller stress responses on the gusset interfaces, as well as smaller shear force and plastic responses on the framing system. Thus, it becomes a promising gusset connection for improved seismic performance of the steel framing system with brace‐type dampers.     

Optimal placement of metallic dampers for seismic upgrading of multistory buildings based on a cost‐effectiveness criterion using genetic algorithm

In this paper, an optimal placement methodology for metallic dampers is proposed to upgrade the seismic performance of multistory buildings. Most previous studies on optimal damper placement (ODP) problems have been focused on minimizing the seismic responses, whereas the present study aims to utilize the minimum total cost of dampers to achieve a prescribed level of seismic response. To this end, the optimization objective is constructed based on a cost‐effectiveness criterion, and the optimization constraint is defined based on a desired level of seismic response. An improved integer‐coded genetic algorithm is presented for solving the ODP problem. A 16‐story shear building is illustrated to verify the proposed optimal placement methodology. It is shown that the proposed methodology can be used to achieve the predetermined performance level while minimizing the retrofitting cost. Moreover, different algorithms, objective functions, and levels of accuracy on the optimization are also compared. Finally, a two‐step optimization approach is proposed for achieving better placement schemes with less computational efforts.