Testing of dynamically substructured,base‐isolated systems using adaptive control techniques

Experimental techniques for testing dynamically substructured systems are currently receiving attention in a wide range of structural, aerospace and automotive engineering environments. Dynamic substructuring enables full‐size, critical components to be physically tested within a laboratory (as physical substructures), while the remaining parts are simulated in real‐time (as numerical substructures). High quality control is required to achieve synchronization of variables at the substructuring interfaces and to compensate for additional actuator system(s) dynamics, nonlinearities, uncertainties and time‐varying parameters within the physical substructures. This paper presents the substructuring approach and associated controller designs for performance testing of an aseismic, base‐isolation system, which is comprised of roller‐pendulum isolators and controllable, nonlinear magnetorheological dampers. Roller‐pendulum isolators are typically mounted between the protected structure and its foundation and have a fundamental period of oscillation far‐removed from the predominant periods of any earthquake. Such semi‐active damper systems can ensure safety and performance requirements, whereas the implementation of purely active systems can be problematic in this respect. A linear inverse dynamics compensation and an adaptive controller are tailored for the resulting nonlinear synchronization problem. Implementation results favourably compare the effectiveness of the adaptive substructuring method against a conventional shaking‐table technique. A 1.32% error resulted compared with the shaking‐table response. Ultimately, the accuracy of the substructuring method compared with the response of the shaking‐table is dependent upon the fidelity of the numerical substructure. Copyright © 2009 John Wiley & Sons, Ltd.     

天然地基强迫振动测试与分析

在试验块体分别为明置与埋置情形时,利用激振器对某工程场地天然地基分别进行竖向、水平回转及扭转稳态强迫振动试验。试验结果表明,埋置情形试验的动力特性参数值均大于明置情形试验相应值;同种试验情形下,地基第一振型共振频率竖向最大,水平回转向其次,扭转向最小;土的参振质量均远大于基础本身质量。     

阿西克剖面记录的西天山地区黄土磁学性质及古气候意义初探

选取阿西克剖面作为研究对象,对伊犁地区末次间冰期以来的沉积的黄土地层的磁学特征进行分析。结果发现,伊犁地区黄土地层的磁性矿物有磁铁矿、磁赤铁矿、赤铁矿、针铁矿,磁学性质受亚铁磁性的磁铁矿（和磁赤铁矿）控制;MD和PSD是地层中亚铁磁性矿物的主要磁畤状态,随着成壤强度增加,地层中的SP和SD颗粒相对含量逐渐增加;亚铁磁性矿物含量与地层并不完全对应。对磁学参数控制机制的分析表明,本剖面磁学性质受控因素比较复杂,磁性矿物含量主要受控于物源的磁学性质,成壤作用对地层中细粒磁性矿物含量具有很大影响,还原作用可能对底部古土壤层的磁学性质造成一定影响,但对整个剖面的磁学性质影响相对较小。     

2008������Ms7.3����ǰ��������̬�仯������

????1998?????????й??????????????????????????2008??3?????????7.3?????????????????????仯?????????????????????????????????????????????????????г????2~10???????????????????????????????????????????????????仯?????????????????????仯????????????????????????????????????????????????????????????????????????????????仯?????????????????????????????1976?????7.8????????????????????????й?????8?????????????仯??200??10 _-8 ms ^-2 ??     

Diagnostic experiments for transport mechanisms of suspended sediment discharged from the Yellow River in the Bohai Sea

Five diagnostic experiments with a 3D baroclinic hydrodynamic and sediment transport model ECOMSED in couple with the third generation wave model SWAN and the Grant–Madsen bottom boundary layer model driven by the monthly sediment load of the Yellow River, were conducted to separately diagnose effects of different hydrodynamic factors on transport of suspended sediment discharged from the Yellow River in the Bohai Sea. Both transport and spatio-temporal distribution of suspended sediment concentration in the Bohai Sea were numerially simulated. It could be concluded that suspended sediment discharged from the Yellow River cannot be delivered in long distance under the condition of tidal current. Almost all of sediments from the Yellow River are deposited outside the delta under the condition of wind-driven current, and only very small of them are transported faraway. On the basis of wind forcing, sediments from the Yellow River are mainly transported north-northwestward, and others which are first delivered to the Laizhou Bay are continuously moved northward. An obvious 3D structure characteristic of sediment transport is produced in the wind-driven and tide-induced residual circulation condition. Transport patterns at all layers are generally consistent with circulation structure, but there is apparent deviation between the depth-averaged sediment flux and the circulation structure. The phase of temporal variation of sediment concentration is consistent with that of the bottom shear stress, both of which are proved to have a ten-day cycle in wave and current condition.     

黄淮海平原农区典型村庄用地扩展及其动力机制

以地处黄淮海平原农区的禹城市伦镇赵庄村为典型案例,利用高分辨率航空遥感数据为基本信息源,结合村庄逐户调查数据,通过土地利用分类与制图,定量研究典型村庄用地格局特征、扩展模式及其动力机制。结果表明:赵庄村土地利用呈"耕地—作业空间—居住空间"的圈层式空间格局。2008年村庄用地规模比1967年增加了1.26倍,主要表现为宅基地的扩展和打谷场用地增长,1985~1990年村庄用地扩展速度最快,村庄用地在空间上向西和向南方向扩展显著。村庄用地扩展主要表现为渐进式蔓延扩展、突变式非地扩展和填充式补充扩展三个阶段。农户居住需求增长与农业生产规模扩大是村庄用地扩展的内生动力,村庄内部条件与外围环境的巨大反差是村庄用地向外扩展的外部环境动力,农户收入增长为村庄用地扩展提供了经济基础,而村庄土地规划缺失与管理缺位使村庄用地扩展失去约束力,这些因素相互作用,共同驱动村庄用地扩展。最后,针对村庄用地扩展存在的问题,提出了促进村庄土地可持续利用的对策建议。     

城市化视角下北京农村居住用地非正规市场的形成机理

针对北京快速城市化影响下的农村居住用地大量非法流转、亟待规范管理等现状特点,选择海淀区肖家河城中村和通州区张家湾镇小产权房分别作为非正规住房租赁市场和非正规土地交易市场,开展微观案例研究。结果表明:城乡二元土地制度是农村居住用地非正规市场形成与发育的制度根源,城市化快速发展与低价住房供应严重不足为其宏观背景,农民对现行土地征用与补偿制度的日益不满和主动争取分享土地增值收益的强烈意愿是其内在原因。非正规市场采用"低成本-低地租-高利润"的微观运作机理,市场参与个体(农民与消费者)可获得较好的经济收益,但也要承担较高的风险;对于城市与社区,非正规市场则会带来较严重的经济社会与资源环境等方面的负面影响。     

长江源区荒漠动态遥感监测及驱动力分析

利用遥感和GIS空间信息分析技术,以长江源地区的4期遥感数据为主要信息源,将荒漠分为高寒荒漠、裸岩石砾地、戈壁、沙地、裸土地、盐碱地,通过目视解译提取了长江源区4期荒漠信息,在此基础上进行荒漠动态变化及驱动力分析。结果表明,长江源区荒漠分布范围较广,荒漠面积占源区总面积的28%左右,荒漠中以高寒荒漠、裸岩石砾地、戈壁、沙地为主,其次是裸土地和盐碱地。近30 a来的变化趋势是20世纪70年代中期到1990年荒漠化发展较快,荒漠面积增加了43 935.00 hm2,1990年到2000年荒漠面积减少了32 821.28 hm2,2000年到2005年荒漠面积增加了29 611.30 hm2。     

中国亚热带地区柑桔气候风险评估

综合考虑柑桔气候适宜性水平及其变率变化,构建柑桔的风险度模型,运用滑动建模技术对中国亚热带地区柑桔的气候风险性进行动态分析与评估。根据风险分布强度将中国亚热带地区柑桔温度、降水、日照和气候风险大致分为三类型:低风险型、中风险型和高风险型。温度风险度大致呈纬度地带性分布,除西部高山区外,由低纬向高纬风险度依次增高;降水风险度呈现亚热带中部低,北部和西部高;与降水风险度相反,日照风险度在亚热带中部高,北部和西部低;气候风险度受温度变化的主导,也大致呈现纬度地带性,呈现高纬和西部高海拔区高,低纬和东部沿海区低。柑桔气候风险在时间和空间变化上都存在着差异,近46年来,中国亚热带地区柑桔气候风险度有逐渐增加的趋势,尤其以20世纪80年代初以来增加的最快;由于全球气候变暖的影响,亚热带东部和南部风险较低的区域分布有逐渐减少的趋势,而北部和西部风险高的区域分布有进一步增大并向东部和南部扩展的可能。从中国亚热带地区柑桔减产率大于10%、20%、30%的气候风险度分布区域变动过程来看,柑桔各减产率的气候风险度分布具有很明显的区域性和连续性,大体上由东南向西北呈增高趋势。     

基于动力学模型的城市资源竞争机制

城市间资源的过度竞争是城市群和谐发展的一大障碍,严重影响了城市群综合竞争力的提高。本文采用动力学模型研究了城市发展与其资源约束的关系,并引入风险规避函数,建立城市资源竞争模型来模拟城市资源竞争的演进机制。分析表明:(1)城市发展与演变过程中,具有较为明显的规模效应,在初期由于集聚效应,城市经济达到一定规模后得以更为迅速的发展;当城市发展规模过大,必然受到自然资源的约束,出现规模效应递减;(2)城市资源竞争是一个非常复杂的动力过程,包括社会经济发展的市场作用,也受到政府行为、科技水平等人类行为因素影响。经济发展战略的选择、人口与科技等相关因素都会对资源竞争的结果产生深刻作用;缩小人均收入与生态效率的差距有助于协调城市间资源竞争关系。