基于加速度反馈的结构地震反应半主动MR阻尼控制试验

本文针对安装有半主动磁流变阻尼器（MR damper)的一座二层模型结构进行了抗震振动台试验研究，通过采用基于加速度反馈控制策略的两种半主动控制算法进行了在各种地震动作用下模型结构的半主动控制的抗震试验研究，并进行了Passive-on和Passive-off两种被动控制的试验研究。试验结果表明，MR阻尼器作为一种半主动控制装置可以有效地控制结构的峰值位移和均方差反应，且半主动控制对结构顶层的峰值位移和均方差的控制效果均优于两种被动控制方法。因此，本文提出的两种半主动控制算法都是有效的，并宜于实现。     

基于可拓工程方法的生态地理区域系统界线划分研究—以中温带半湿润、半干旱

利用可拓工程方法中的物元模型对生态地理区域系统的界线问题进行了研究，通过选取样本和指标对单指标关联函数和多指标综合关联函数进行了定量计算。在此基础上，通过专家集成确定了中国中温带半湿润、半干旱区之间的界线，弥补了单指标和定性划分的不足，有助于中国生态地理区域系统的构建。     

半热带气旋大暴雨天气的初步分析

对１９９５年８月１４－１７日山东连续大暴雨天气进行了分析与研究，指出了半热带地山东大暴雨天气的作用，进一步揭示出半热带气旋大暴雨天气的物理机制。     

物理守恒律保真格式构造与数值预报斜压原始方程传统谱模式改进研究

文中构造并证明了一般二次和三次物理守恒律时间差分保真格式两个构造定理，以往一些主要时间离散守恒格式构造方案可作为两个定理特例给出。它们不仅可为解决更加广泛类别的时间离散保真格式构造基本问题提供适用数学基础，而且也为结合已有瞬时空间离散守恒格式，解决更加广泛类别的时－空离散意义下保真格式构造基本问题提供适用的数学基础。此外，文中两个定理还可解决两大类问题的线性和非线性计算不稳定性问题。斜压原始方程传统半隐式全球谱－垂直有限差分模式目前是世界上许多国家的业务预报和大气环流模式。本工作利用文中新构定理，构造并且实现了斜压原始方程全球谱－垂直有限差分模式半隐式高阶全能量守恒方案。以往该项基本问题无论在理论还是实践上长期以来一直都未能得到解决。该项全能量守恒半隐式全球谱模式方案适用于实测资料的长时间数值预报积分。使用ＦＧＧＥ夏季资料进行的１３个个例３０ｄ数值积分实验表明：新型全能量半隐式保真方案可以有效地改进传统预报方案中关于能量质量守恒性质的系统性偏差。值得注意的是，实验统计分析还显示：在本文实验条件下，传统方案中由于时间离散过程中原物理守恒律性质破坏导致的系统误差（简称Ｚ类误差），对于实验总体均方根系统误差的贡献     

中国干旱-半干旱区当代气候变化

本文在作者近年有关研究工作的基础上，结合最新资料和有关成果，对我国干旱－半干旱区当代气候变化做了比较系统的分析。结果表明，中国干旱－半干旱区气候变化与全国和北半球气候变化相比有一定的特点。冬夏温度变化不同，干旱－半干旱区降水变化趋势不同。     

The lost city of north‐west Queensland: a test of the model of giant Grikeland development in semi‐arid Karst

Jennings and Sweeting's (1963) model of landscape evolution in the Limestone Ranges of Western Australia has been proposed as a general scheme of semi‐arid karstification by Williams (1978) and Ford and Williams (1989). The model involves an initial plateau surface which undergoes progressive karstic dissection. The resultant landscape is characterised first by giant grikelands, then by box valleys and finally by karst towers. The depth of dissection is governed by the altitude of successive levels of pediplanation adjacent to the karst, with each karst level representing the location of a former erosion surface. The Lost City, a giant grikeland in the Barkly karst of north‐west Queensland, has evolved by the karstic dissection and stripping of a gently dipping sequence of carbonates and cherts. By contrast with the type example, the depth of dissection, the altitude of successive surfaces, the form and even the location of the grikeland are all controlled by rock structure. Not only does this cast doubt on the general applicability of Jennings and Sweeting's model, it suggests that such landscapes may also be the result of structural control and that the role played by semi‐arid climates may be less important than has previously been proposed. Given our present poverty of knowledge of semi‐arid karstification, any attempt to identify type examples of semi‐arid karst may be premature.     

The influence of bedrock‐derived acidity in the development of surface and underground karst: evidence from the Precambrian carbonates of semi‐arid northeastern Brazil

Very extensive cave systems are developed in Precambrian Una Group carbonates in the Campo Formoso area, eastern Brazil. In contrast, the area is largely devoid of significant surface karst landforms, as would be expected given its semi‐arid climate. The caves in the area display many morphological features characteristic of deep‐seated hypogenic caves, such as lack of relationship with the surface, ramiform/network pattern, abrupt variations of passage cross‐sections and absence of fluvial sediments, but do not show evidence of vertical passages marking the ascending path of acidic water nor present extensive gypsum or acid clay mineral deposits. Hydrochemical analyses of present‐day ground water indicate that oxidation of bedrock sulphide is an active process, and sulphuric acid may be the main agent driving carbonate dissolution in the area. A shallow mode of speleogenesis is thus proposed, in which sulphuric acid produced through the oxidation of sulphide beds within the carbonates controls cave initiation and development. Moreover, the geological situation of the area in an ancient stable passive margin precludes the possibility of deep‐seated sources of acidity. Under dry climate, due to the absence of recharge, solutional landforms will be largely subdued in the surface. Hypogenic processes, if present, are likely to predominate, producing a landscape characterized by a marked disparity in the comparative degree of development between surface and underground landforms. Rates of karst landform development have traditionally been analysed through a climatic perspective, runoff being the main controlling factor in promoting karst development. This view needs to be reassessed in the light of the growing awareness of the importance of climate‐independent processes related to hypogenic sources of acidity. Copyright © 2003 John Wiley & Sons, Ltd.     

Predictive control of seismic structures with semi‐active friction dampers

In this paper a predictive control method especially suitable for the control of semi‐active friction dampers is proposed. By keeping the adjustable slip force of a semi‐active friction damper slightly lower than the critical friction force, the method allows the damper to remain in its slip state throughout an earthquake of arbitrary intensity, so the energy dissipation capacity of the damper can be improved. The proposed method is formulated in a discrete‐time domain and cast in the form of direct output feedback for easy control implementation. The control algorithm is able to produce a continuous and smooth slip force for a friction damper and thus avoid exerting the high‐frequency structural response that usually exists in structures with conventional friction dampers. Using a numerical study, the control performance of a multiple degrees of freedom (DOF) structural system equipped with passive friction dampers and semi‐active dampers controlled by the proposed method are compared. The numerical case shows that by merely using a single semi‐active friction damper and a few sensors, the proposed method is able to achieve better acceleration reduction than the case using multiple passive dampers. Copyright © 2004 John Wiley & Sons, Ltd.     

Semi‐active fuzzy control for seismic response reduction using magnetorheological dampers

A semi‐active fuzzy control strategy for seismic response reduction using a magnetorheological (MR) damper is presented. When a control method based on fuzzy set theory for a structure with a MR damper is used for vibration reduction of a structure, it has an inherent robustness, and easiness to treat the uncertainties of input data from the ground motion and structural vibration sensors, and the ability to handle the non‐linear behavior of the structure because there is no longer the need for an exact mathematical model of the structure. For a clipped‐optimal control algorithm, the command voltage of a MR damper is set at either zero or the maximum level. However, a semi‐active fuzzy control system has benefit to produce the required voltage to be input to the damper so that a desirable damper force can be produced and thus decrease the control force to reduce the structural response. Moreover, the proposed control strategy is fail‐safe in that the bounded‐input, bounded‐output stability of the controlled structure is guaranteed. The results of the numerical simulations show that the proposed semi‐active control system consisting of a fuzzy controller and a MR damper can be beneficial in reducing seismic responses of structures. Copyright © 2004 John Wiley & Sons, Ltd.     

流体——重力式锥状单腿平台结构——土相互作用体系的地震动力响应

本文用配点法对流体——重力式锥状单腿平台结构——土相互作用体系在地震作用下的动力响应问题进行了研究。采用频域分析法，将锥柱体Ｎ等分，利用运动方程和边界条件联立解方程组，继而求出平台结构顶端弹性位移和腿柱所受的动水压力、基础平移和基础转角的频响函数。分析不同锥角下体系的动力响应的影响，并分析研究了刚性地基和考虑土——结构相互作用时结构体系的动力响应情况，得到一些很有益的结果。