脱层材料与槽接式挫屈束制支撑的性能研究

挫屈束制支撑耐震性能优劣与否与脱层材料性能有密切关系,首先提出了一种估算脱层不完全因子的方法,利用4组分别使用不同脱层材料的挫屈束制支撑进行构件试验;研究结果表明以黏性橡胶作为脱层材料具有可靠性、经济性与优良的施工性。特别介绍了地震工程研究中心近期所研发的槽接式挫屈束制支撑,并通过3组实尺寸构件试验验证了其耐震性能;测试构件包含一组长度为12.5m,最大抗压强度超过16800kN,核心消能段应变量达3.5%的构件。试验结果表明,新研发的槽接式挫屈束制支撑经济效益极高,迟滞消能行为良好稳定,具有优良的耐震性能,各组试体于试验停止前所累积的总非线性变形量皆超过400倍斜撑屈曲位移量;研究亦显示,非线性结构分析软件PISA3D可准确预测其受力与变形反应。     

Developing multiple regression models from the manufacturer's ground-source heat pump catalogue data

The performance of ground-source heat pumps (GSHP), often expressed as Power drawn and/or the COP, depends on several operating parameters. Manufacturers usually publish such data in tables for certain discrete values of the operating fluid temperatures and flow rates conditions. In actual applications, such as in dynamic simulations of heat pump system integrated to buildings, there is a need to determine equipment performance under operating conditions other than those listed. This paper describes a simplified methodology for predicting the performance of GSHPs using multiple regression (MR) models as applicable to manufacturer data. We find that fitting second-order MR models with eight statistically significant x-variables from 36 observations appropriately selected in the manufacturer catalogue can predict the system global behavior with good accuracy. For the three studied GSHPs, the external prediction error of the MR models identified following the methodology are 0.2%, 0.9% and 1% for heating capacity (HC) predictions and 2.6%, 4.9% and 3.2% for COP predictions. No correlation is found between residuals and the response, thus validating the models. The operational approach appears to be a reliable tool to be integrated in dynamic simulation codes, as the method is applicable to any GSHP catalogue data.     

An unsupervised learning method with a clustering approach for tumor identification and tissue segmentation in magnetic resonance brain images

Malignant and benign types of tumor infiltrated in human brain are diagnosed with the help of an MRI scanner. With the slice images obtained using an MRI scanner, certain image processing techniques are utilized to have a clear anatomy of brain tissues. One such image processing technique is hybrid self-organizing map (SOM) with fuzzy K means (FKM) algorithm, which offers successful identification of tumor and good segmentation of tissue regions present inside the tissues of brain. The proposed algorithm is efficient in terms of Jaccard Index, Dice Overlap Index (DOI), sensitivity, specificity, peak signal to noise ratio (PSNR), mean square error (MSE), computational time and memory requirement. The algorithm proposed through this paper has better data handling capacities and it also performs efficient processing upon the input magnetic resonance (MR) brain images. Automatic detection of tumor region in MR (magnetic resonance) brain images has a high impact in helping the radio surgeons assess the size of the tumor present inside the tissues of brain and it also supports in identifying the exact topographical location of tumor region. The proposed hybrid SOM-FKM algorithm assists the radio surgeon by providing an automated tissue segmentation and tumor identification, thus enhancing radio therapeutic procedures. The efficiency of the proposed technique is verified using the clinical images obtained from four patients, along with the images taken from Harvard Brain Repository.     

Active tuned mass damper for damping of offshore wind turbine vibrations

An active tuned mass damper (ATMD) is employed for damping of tower vibrations of fixed offshore wind turbines, where the additional actuator force is controlled using feedback from the tower displacement and the relative velocity of the damper mass. An optimum tuning procedure equivalent to the tuning procedure of the passive tuned mass damper combined with a simple procedure for minimizing the control force is employed for determination of optimum damper parameters and feedback gain values. By time domain simulations conducted in an aeroelastic code, it is demonstrated that the ATMD can be used to further reduce the structural response of the wind turbine compared with the passive tuned mass damper and this without an increase in damper mass. A limiting factor of the design of the ATMD is the displacement of the damper mass, which for the ATMD, increases to compensate for the reduction in mass. Copyright © 2016 John Wiley & Sons, Ltd.     

Hybrid damper with stroke amplification for damping of offshore wind turbines

The magnitude of tower vibrations of offshore wind turbines is a key design driver for the feasibility of the monopile support structure. A novel control concept for the damping of these tower vibrations is proposed, where viscous‐type hybrid dampers are installed at the bottom of the wind turbine tower. The proposed hybrid damper consists of a passive viscous dashpot placed in series with a load cell and an active actuator. By integrated force feedback control of the actuator motion, the associated displacement amplitude over the viscous damper can be increased compared with the passive viscous case, hereby significantly increasing the feasibility of viscous dampers acting at the bottom of the wind turbine tower. To avoid drift in the actuator displacement, a filtered time integration of the measured force signal is introduced. Numerical examples demonstrate that the filtered time integration control leads to performance similar to that of passive viscous damping and substantial amplification of the damper deformation without actuator drift. Copyright © 2016 John Wiley & Sons, Ltd.     

设置FPS质量调谐阻尼器减振效果分析研究

根据拉格朗日方程推导了结构设置FPS调谐质量系统地震动力反应分析计算公式,并考虑了接触面滞滑效应的影响。分析与计算结果表明:设置质量调谐系统之后,结构动力反应层间位移有所减小。当接触面滑动摩擦系数为0.15左右、滑道半径为0.7 m、调谐附加质量为楼层质量的1.4倍以上时,质量调谐系统具有较好的减振效果、消能效果与复位能力。     

SLR算法在MRI中的模拟方法与实验研究

在磁共振成像中,运用Shinnar-Le Roux算法设计射频脉冲,不仅可以避免Bloch方程引起的非线性问题,而且能有效地抑制旁瓣激发,以获得理想的激发带宽.首先介绍了SLR脉冲设计思想,然后基于密度矩阵理论,应用计算机模拟方法对所设计脉冲的激发带宽进行模拟.最后,给出了测量射频脉冲激发带宽曲线的脉冲序列,并用MRI实验加以验证.     

磁流变阻尼器性能试验研究

基于磁流变阻尼器的性能试验，对磁流变阻尼器的阻尼力性能进行了研究，得出力一位移的滞回曲线和力一速度曲线，并分析了影响阻尼力的各种因素，从而总结出磁流变阻尼器的阻尼力性能。     

降低架空输电线路防振锤滑移率的研究

在架空输电线路的导、地线上安装防振锤,是防止架空输电线路导、地线因为振动而出现断线、断股事故的主要措施之一。但由于各种原因的作用,防振锤在安装一段时间后滑移出原有的安装位置,失去防振作用,威胁导、地线安全运行。分析了防振锤出现滑移的各种原因,并对现使用的防振锤结构提出改进措施,取得了较好的效果。