Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters

The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.     

城市节水工作存在的问题及对策研究

水资源匮乏已成为当今社会发展不可回避的主要问题，成为制约国民经济快速、稳定、健康发展的“瓶颈”，解决这一问题成为当务之急，本文就城市节水存在的问题，提出了加强节水管理的综合性措施。     

The inversion of anelastic coefficient,source parameters and site respond using genetic algorithm

It gradually becomes a common work using large seismic wave data to obtain source parameters, such as seismic moment, break radius, stress drop, with completingof digital seismic network in China (Hough, et al, 1999; Bindi, et al, 2001). These parameters are useful on earthquake prediction and seismic hazard analysis.Although the computation methods of source parameters are simple in principle and the many research works have been done, it is not easy to obtain the parameters accurately. There are two factors affecting the stability of computation results. The first one is the effect of spread path and site respond on signal. According to the research results, there are different geometrical spreading coefficients on different epicenter distance. The better method is to introduce trilinear geometrical spreading model (Atkinson, Mereu, 1992; Atkinson, Boore, 1995; WONG, et al, 2002). In addition, traditional site respond is estimated by comparing with rock station, such as linear inversion method (Andrews, 1982), but the comparative estimation will introduce some errors when selecting different stations. Some recent research results show that site respond is not flat for rock station (Moya, et al, 2000; ZHANG,. et al, 2001; JIN, et al, 2000; Dutta, et al, 2001). The second factor is to obtain low-frequency level and corner frequency fromdisplacement spectrum. Because the source spectrum model is nonlinear function,these values are obtained by eye. The subjectivity is strong. The small change of corner frequency will affect significantly the result of stress drop.     

Re-discussion on the Jiaochang Arcuate Structure, Sichuan Province, and the Seismogenic Structure for Diexi Earthquake in 19331

The Jiaocbang arcuate structure is one of the numerous arcuate structural belts in Sichuan. The present paper gives a further argument about the characteristics of that arcuate structure and the new activity of the Songpinggou fault and affirms that the Songpinggou fault is an active fault in the Holocene epoch. The Diexi M7.5 earthquake took place in 1933 on the west wing of that arcuate structure, near the apex of the arc. Many authors have given quite different opinions about the genetic structure of that earthquake. The authors have made on-the-spot investigations time and again over recent years. Besides this, the authors have also further studied the shape of intensity contour lines, the distribution characteristics of ground surface seismic hazards, the left-lateral dislocation of buildings along the Songpinggou fault, the NWtrending ground fissures that developed on the ground surface after earthquake, and so on. On this basis, it is still considered that the seismogenic fault of the 1933 Diexi M7.5 earthquake was the Songpinggou fault on the west wing of the Jiaochang arcuate structure.     

易门式大型铜矿床构造成矿动力学模型

针对金属矿床隐伏矿定位预测的关键问题,在提出构造成矿动力学的分支学术方向的基础上,以易门式大型铜矿床为例,从成矿地质背景、矿田构造、构造地球化学和成矿构造应力场等方面进行构造成矿动力学研究,阐述在构造应力场控制下成矿流体运移和聚集的规律。构造地球化学研究认为,构造地球化学异常反映矿体的原生晕;构造地球化学异常受构造控制,其分带特征可指示成矿流体的流向,并提供矿床成因和隐伏矿(化)体相对埋深的信息。构造应力场的控矿特征主要表现在:构造应力场导致控矿构造的形成,并驱动成矿流体的运移;构造应力场控制了成矿能量场;应力和能量的高值集中区分布特点可反映某些构造型式。在此基础上建立构造成矿动力学模型,概括隐伏矿成矿预测准则,据此提出若干重点找矿靶区和靶位,其中部分靶区得到工程验证,表明构造成矿动力学方法对隐伏矿定位预测和评价具有重要的指导意义。     

Field Survey and Numerical Simulations: A Review of the 1998 Papua New Guinea Tsunami

— The Papua New Guinea (PNG) tsunami of 1998 is re-examined through a detailed review of the field survey as well as numerous numerical computations. The discussion of the field survey explores a number of possible misinterpretations of the recorded data. The survey data are then employed by a numerical model as a validation tool. A Boussinesq model and a nonlinear shallow water wave (NLSW) model are compared in order to quantify the effect of frequency dispersion on the landslide-generated tsunami. The numerical comparisons indicate that the NLSW model is a poor estimator of offshore wave heights. However, due to what appears to be depth-limited breaking seaward of Sissano spit, both numerical models are in agreement in the prediction of maximum water elevations at the overtopped spit. By comparing three different hot-start initial profiles of the tsunami wave, it is shown that the initial shape and orientation of the tsunami wave is secondary to the initial displaced water mass in regard to prediction of water elevations on the spit. These numerical results indicate that agreement between numerical prediction of runup values with field recorded values at PNG cannot be used to validate either a NLSW tsunami propagation model or a specific landslide tsunami hot-start initial condition. Finally, with the use of traditional tsunami codes, a new interpretation of the PNG runup measurements is presented.     

SHRIMP U-Pb zircon age,geochemistry and Nd isotope of the Guandaoshan pluton in SW Sichuan: Petrogenesis and tectonic significance

SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neo-proterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857 ± 13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neo-proterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860–750 Ma mantle superplume beneath the supercontinent Rodinia.     

基于GPS基准站网的GPS测量

采用基于GPS基准网的GPS测量可以提高GPS测量的可靠性和准确性 ,可以消除和减小GPS测量观测值中与时间和空间相关的大气误差和轨道误差的影响 ,使中、长距离快速静态定位和RTK动态定位成为现实 ,还具有可直接得到WGS84Z坐标等优点。本文介绍基于GPS基准站网的GPS测量 ,简要地论述GPS虚拟参考站法VRS和区域改正数法FKP的原理、方法和特点 ,以及目前实施中存在的一些问题     

Computer Simulation of Shaped Charge Detonation Using Meshless Particle Method

Shaped charges are widely applied in the defense industry and civil engineering for penetrating hardened targets. Simulations of shaped charges are generally based on traditional grid-based numerical methods. Different from the existing literature, the SPH method is applied in this paper to simulate the detonation process of shaped charge explosive. The combination of the meshless, Lagrangian and particle nature inherent in the SPH method is very attractive in dealing with large deformations and large inhomogeneities in extremely transient situations such as detonation process. The SPH method and some related numerical aspects are briefly discussed first, followed by applications in simulating shaped charge detonations. The effects of different detonation cavity angles and different charge head lengths are investigated. The results demonstrate that major shaped charge detonation phenomena are captured with revealing observations.     

Desorption kinetics of radiocesium from subsurface sediments at Hanford Site, USA

The desorption of ¹³⁷Cs⁺ was investigated on sediments from the United States Hanford site. Pristine sediments and ones that were contaminated by the accidental release of alkaline ¹³⁷Cs⁺-containing high level nuclear wastes (HLW, 2 × 10⁶ to 6 × 10⁷ pCi ¹³⁷Cs⁺/g) were studied. The desorption of ¹³⁷Cs⁺ was measured in Na⁺, K⁺, Rb⁺, and NH₄⁺electrolytes of variable concentration and pH, and in presence of a strong Cs⁺-specific sorbent (self-assembled monolayer on a mesoporous support, SAMMS). ¹³⁷Cs⁺ desorption from the HLW-contaminated Hanford sediments exhibited two distinct phases: an initial instantaneous release followed by a slow kinetic process. The extent of ¹³⁷Cs⁺ desorption increased with increasing electrolyte concentration and followed a trend of Rb⁺ ≥ K⁺ > Na⁺ at circumneutral pH. This trend followed the respective selectivities of these cations for the sediment. The extent and rate of ¹³⁷Cs⁺ desorption was influenced by surface armoring, intraparticle diffusion, and the collapse of edge-interlayer sites in solutions containing K⁺, Rb⁺, or NH₄⁺. Scanning electron microscopic analysis revealed HLW-induced precipitation of secondary aluminosilicates on the edges and basal planes of micaceous minerals that were primary Cs⁺ sorbents. The removal of these precipitates by acidified ammonium oxalate extraction significantly increased the long-term desorption rate and extent. X-ray microprobe analyses of Cs⁺-sorbed micas showed that the ¹³⁷Cs⁺ distributed not only on mica edges, but also within internal channels parallel to the basal plane, implying intraparticle diffusive migration of ¹³⁷Cs⁺. Controlled desorption experiments using Cs⁺-spiked pristine sediment indicated that the ¹³⁷Cs⁺ diffusion rate was fast in Na⁺-electrolyte, but much slower in the presence of K⁺ or Rb⁺, suggesting an effect of edge-interlayer collapse. An intraparticle diffusion model coupled with a two-site cation exchange model was used to interpret the experimental results. Model simulations suggested that about 40% of total sorbed ¹³⁷Cs⁺ was exchangeable, including equilibrium and kinetic desorbable pools. At pH 3, this ratio increased to 60-80%. The remainder of the sorbed ¹³⁷Cs⁺ was fixed or desorbed at much slower rate than our experiments could detect.