磁流变变阻尼半主动控制结构的仿真分析   总被引：6，自引：2，他引：6  

付伟庆  王玉铨  王焕定  张永山 《地震工程与工程振动》2003,23(4):165-170

由于高阶单步法已成功地应用于结构非线性分析及考虑时滞的主动控制等，显示了它的稳定、精度高和计算迅速等特点。用于结构振动控制的磁流变阻尼器属于速度相关型变阻尼半主动控制器，已有的一些算法，或因计算时间过长不能用于实际控制，或因需要事先经过学习训练，控制效果取决于训练学习的情况。因此，本文将高阶单步法应用于磁流变变阻尼半主动控制系统，采用开关控制和连续控制两种控制率对磁流变液的剪切强度进行调节。仿真计算表明，该控制算法是一种能用于结构实际控制的变阻尼有效算法.  相似文献   

Gravity interpretation of nonoutcropping sedimentary basins in which the density contrast decreases parabolically with depth     

V. Chakravarthi 《Pure and Applied Geophysics》1995,145(2):327-335

The decrease in density contrast of sedimentary rocks with depth in many sedimentary basins can be approximated by a parabolic density function. Analytical gravity expression of an outcropping two-dimensional vertical step along which the density contrast decreases parabolically with depth is derived in the space domain. A modification ofBott's (1960) method of gravity interpretation is proposed by considering two outcropping vertical steps on either side of the first and last observation points in addition toN outcropping vertical prisms in order to interpret the gravity anomalies of nonoutcropping basins. The thicknesses of the two outcropping vertical steps are made equal to the thicknesses of the two outcropping vertical prisms placed below the first and last observation points. The initial depth estimates of the sedimentary basin are calculated by the infinite slab formula ofVisweswara Rao et al. (1993). The gravity effects of theN outcropping prisms and the two outcropping vertical steps are calculated at each anomaly point and the depth to the floor of the basin are adjusted based on the differences between the observed and calculated anomalies. A gravity anomaly profile of Los Angeles basin, California is interpreted.  相似文献   

自然金{110}晶面微形貌的STM观察   总被引：1，自引：0，他引：1  

廖立兵  白春礼 《矿物岩石》1995,15(2):1-5

自然金常呈不规则粒状或团块状产出，规则晶体少见，因此自然金晶体的晶面形貌研究资料不多。作者用扫描隧道显微镜对自然金菱形十二面体晶面进行观察，获得金（Ａｕ）（１１０）晶面一系列微形貌图象，并从晶体生长和晶体结构的角度讨论了各种微形貌现象的成因。  相似文献   

保径导向扩孔钻头的设计及其工程应用          下载免费PDF全文

何玉云  王发民 《探矿工程》2019,46(11):50-53

岩心钻探中,在砾石（漂砾）等破碎地层采用常规三翼扩孔钻头扩孔时,常出现憋车和卡钻现象,且扩孔效率低。为此,设计了具有导向和保径功能的扩孔钻头。新设计的扩孔钻头在宁夏灵武一个综合地质孔进行了应用,扩孔效果良好,平均扩孔效率3.5 m/h,形成的新孔眼与原孔眼同轴度高,孔径规则,下套管顺利,对第四系破碎地层进行了有效分隔,保障了后续取心钻进和物探测井的顺利进行。  相似文献   

倾斜台阶重力异常正演计算公式剖析     

马国庆  李宗睿  李丽丽 《世界地质》2019,(2):454-460

规则地质体的正演异常是进行实际数据解释的依据,因此其正确性至关重要。现有教材和大部分论文中所列出的倾斜台阶重力异常正演公式在一定条件下会出现畸点,从而对构造模型的数据解释会产生困扰。笔者从台阶的重力积分表达式出发,重新推导了倾斜台阶模型的重力异常正演公式,模型试验表明笔者新推导公式不会出现畸点,这为数据解释提供更准确的基础数据。  相似文献   

三维复杂构造中地震波模拟的单程波方法   总被引：22，自引：10，他引：12       下载免费PDF全文

刘礼农  崔凤林  张剑锋 《地球物理学报》2004,47(3):514-520

复杂构造中单程波与双程波方法模拟结果的比较表明,就地震勘探中主要关心的一次反射波而言,单程波算法已具有足够的精度. 使用单程波方程将极大地减少数值计算的计算量,同时对介质的几何和物理参数建模也降低了要求. 单程波算法可视为深度偏移的“逆运算”,这样可以很好地借用已知的深度偏移方法及其程序系统. 基于计算效率和计算精度的双重考虑,本文在介质速度结构较复杂时采用显式短算子波场延拓方法,而在介质速度结构相对简单时采用分裂步相移法. 反射系数的计算中考虑了其随入射角的变化.  相似文献   

三维非均匀介质中真振幅地震偏移算子研究   总被引：31，自引：6，他引：25       下载免费PDF全文

崔兴福  张关泉  吴雅丽 《地球物理学报》2004,47(3):509-513

利用三维非均匀介质中的波动方程,进行振幅保真波场偏移算子分解,得到用于真振幅偏移的单程波方程. 经过数学推理,导出裂步Fourier法真振幅偏移和Fourier有限差分法真振幅偏移的算子方程,并给出其具体的实现过程.  相似文献   

郯庐断裂带中段幔源包体单矿物中的气体释放特征与成因     

马锦龙  陶明信  叶先仁  张小军 《沉积学报》2004,22(1):176-181

地幔流体对探讨地球深部地质作用意义重大。对山东境内幔源包体矿物的分步加热表明其气体的释放有一定的规律性 :随温度升高,总释气量逐渐增加,至 6 5 0～ 80 0℃出现释气峰,随后释气量逐渐降低。气体各主要组分的释放特征是 :5 0 0℃总有CH₄释气峰;随温度升高,H₂ 释放呈增加趋势,而CO₂ 呈降低趋势,反映其各自赋存状态的差异和加热过程中可能发生的相互转化作用。根据各温度段气体组成特征,单矿物的释气特征可明显分为三个阶段,它们可能代表了矿物中不同演化阶段的气体.  相似文献   

浅埋煤层长壁开采顶板岩层灾害控制研究     

杨治林 《岩土力学》2011,32(Z1):459-0463

根据浅埋煤层顶板岩层的赋存特点和长壁开采时基岩老顶的断裂下沉特征,应用初始后屈曲理论和突变理论探讨了初次来压期间基岩老顶的灾害机制和灾害控制,补充了基岩老顶破断后控制岩块滑落失稳的充分条件和岩块触矸前后台阶下沉的判据,确定了台阶下沉量,给出了控制台阶下沉和维持顶板稳定的支护力计算公式,并以神东矿区大柳塔1203工作面为例给出了工程实例。研究发现,顶板破断后岩块处于不平衡状态,台阶下沉的机制是结构的滑落失稳;岩块触矸前后的台阶下沉分别与断裂下沉和开采高度之间存在着确定的关系;顶板强烈来压主要是由结构滑落失稳造成的,控制台阶下沉的实质是控制岩块沿煤壁的滑落失稳。研究结果表明,综合应用初始后屈曲理论和突变理论,可根据顶板结构的赋存状况和结构特征,确定基岩老顶触矸前是否会出现全厚度切落;根据工作面的开采高度和采空区有效充填厚度等,可确定基岩老顶触矸后岩块的运动形式;根据顶板的破断步距、断裂下沉量和岩块摩擦因数等,可确定岩块触矸前后控制台阶下沉的支护力  相似文献   

Insights on the kinematics of deep-seated gravitational slope deformations along the 1915 Avezzano earthquake fault (Central Italy), from time-series DInSAR     

M. Moro  M. Saroli  C. Tolomei  S. Salvi 《Geomorphology》2009,112(3-4):261-276

Small meandering channels of about 1 m wide on an intertidal mudflat in the Westerschelde estuary the Netherlands) were studied with the aim to improve understanding of the effect of highly cohesive bed and bank sediment on channel inception and meander geometry and dynamics. The study is supported by experiments and modelling. The estuarine meandering channels are less dynamical than alluvial meandering rivers, and the dynamics are more localised. Moreover, the high thresholds for bed sediment erosion and for bank failure lead to two processes, uncommon in larger rivers, that cause most of the morphological change. First, the beds of the channels are eroded by backward migrating steps under hydraulic jumps, while the remainder of the bed surface along the channel is hardly eroded. Second, channel banks erode i) where eroding steps locally cause undercutting of otherwise stable channel banks and ii) in very sharp bends where the flow separates from the inner-bend channel boundary and impinges directly on the bank on the opposite side of the channel. Further morphological change is probably induced by rainfall splash erosion and by storm waves that weaken the mud, and by large mud fluxes from the estuary. The steps were successfully reproduced in laboratory flume experiments. An existing model for step migration predicted celerities consistent with field and laboratory observations and demonstrated a strong dependence on the threshold for erosion. Bank stability models confirm that banks and steps only fail when undercut and weakened by waves, rain or excess pore pressure in agreement with observations. The effects of a high threshold for bank erosion was implemented in an existing meander simulation model that reproduced the observed locations of bank erosion somewhat better than without the threshold, but flow separation and its effect on meander bends remains poorly understood.  相似文献