A seismic retrofit method by connecting viscous dampers for microelectronics factories

The implementation of viscous dampers to microelectronics factories has been previously proved not to affect the micro‐vibration of the factories in operation so that the vibration‐sensitive manufacturing process will not be interfered. Therefore, a seismic retrofit strategy which employs the viscous dampers installed in between the exterior and interior structures of the ‘fab’ structure is proposed in the study. The design formulas corresponding to the proposed retrofit method are derived using the non‐proportional damping theory. Based on the study, it is found that the added damping ratio to the fab structure depends greatly on the frequency ratio of the two structures in addition to the damping coefficients of the added dampers. Outside the bandwidth of the frequency ratio in which the added damping ratio is very sensitive to the variation of the frequency ratio, the added damping ratio can be well captured using the classical damping theory. Copyright © 2007 John Wiley & Sons, Ltd.     

Pressure Variations with Depth in Aquifers with or without Groundwater Leakage

Hydrodynamic analysis allowed establishing elevated hydrodynamic pressure in aquifers in the case of ascending groundwater movement from one layer to another as compared with the pressure in the case, where there is no leakage. In the case of descending movement of groundwater with leakage from layer to layer, the hydrodynamic pressure was found to be lower. Equations are given that allow calculating water leakage and the part of the hydrodynamic pressure that is caused by water leakage from layer to layer. For concrete hydrogeological conditions, estimates are given for the hydrodynamic pressure and its part determined by water leakage between aquifers and from layer to layer in the case of ascending and descending groundwater flows.     

A multigrid solver for 3D electromagnetic diffusion

The performance of a multigrid solver for the time‐harmonic electromagnetic problem in geophysical settings is investigated. The frequencies are sufficiently small for waves travelling at the speed of light to be negligible, so that a diffusive problem remains. The discretization of the governing equations is obtained by the finite‐integration technique, which can be viewed as a finite‐volume generalization of Yee's staggered grid scheme. The resulting set of discrete equations is solved by a multigrid method. The convergence rate of the multigrid method decreased when the grid was stretched. The slower convergence rate of the multigrid method can be compensated by using bicgstab2 , a conjugate‐gradient‐type method for non‐symmetric problems. In that case, the multigrid solver acts as a preconditioner. However, whereas the multigrid method provides excellent convergence with constant grid spacings, it performs less than satisfactorily when substantial grid stretching is used.     

A simple pore water hydrogen diffusion syringe sampler

Molecular hydrogen (H(2)) is an important intermediate product and electron donor in microbial metabolism. Concentrations of dissolved H(2) are often diagnostic of the predominant terminal electron-accepting processes in ground water systems or aquatic sediments. H(2) concentrations are routinely measured in ground water monitoring wells but are rarely measured in saturated aquatic sediments due to a lack of simple and practical sampling methods. This report describes the design and development (including laboratory and field testing) of a simple, syringe-based H(2) sampler in (1) saturated, riparian sediments, (2) surface water bed sediments, and (3) packed intervals of a fractured bedrock borehole that are inaccessible by standard pumped methods.     

A thin film approach for producing mineral diffusion couples

Few diffusion coefficient values have been measured for silicate minerals at pertinent geologic conditions because of experimental restrictions. Until recently, analysis of diffusion couples was conducted principally with electron microprobes which have rather poor spatial resolution (micrometer scale). Ion microprobe analyses, however, eliminate many of the previous experimental restrictions; in depth profile mode they have excellent spatial resolution (tens of angstroms) and diffusion couples can be analyzed normal to the interface. Diffusion couples analyzed by ion microprobe must be well-defined and uniform; previous methods using solution precipitates to form the diffusion couples were heterogeneous and had limited success. A new approach, the thermal evaporation of²⁵MgO under high vacuum onto a crystalline substrate (oxide, silicate), produces a 1000 Å thick²⁵MgO _x (x<1) thin film. This method yields an excellent diffusion couple for low-temperature diffusion experiments. Diffusion anneal experiments using this approach for garnet provide a Mg self-diffusion coefficient ofD=0.60±0.09×10^–21 m²/s at 1000°C (logFO₂=–11.3,P=1 atm,X _Almandine=0.24).     

Extreme fractionation in felsic magma chambers: a product of liquid-state diffusion or fractional crystallization?

Extreme fractionation of minor and trace elements commonly accompanies very modest changes in major element concentrations in highly felsic igneous sequences. In such sequences, Si increases by only a few percent while, for example, Sr, Ba, Mg, and light rare earth elements decrease drastically, commonly by a factor of 10 or more. It has been argued, most notably by Hildreth (e.g. [1]), that such trends observed in tuffs were not induced by fractional crystallization (FC), but rather are a manifestation of compositional gradients in parental magma chambers which form via liquid-state thermogravitational diffusion (LSTD). The strongest arguments against FC are that (1) crystal settling is not a viable mechanism for crystal-liquid separation, and (2) extensive recrystallization is required to produce the observed trends, yet the tuffs are relatively crystal-poor. Many workers have noted trends in plutonic as well as volcanic rocks which are strikingly similar to those for which LSTD has been proposed, and some have concluded that LSTD was the fractionating mechanism.Several lines of evidence lead us to the conclusion that FC is the dominant differentiating process in high-silica magmas: (1) elemental trends are strikingly consistent with those predicted for FC; it would be a remarkable coincidence if diffusion-induced trends mimicked FC so closely; (2) large phenocryst assemblages in high-silica tuffs indicate low-variance liquid compositions that would be improbable if crystal-liquid equilibria were not controlling differentiation; (3) highly evolved plutonic rocks in many cases do not form the caps expected for LSTD, but rather occur in dikes and pods where they apparently segregated as late liquids; (4) recent experimental studies suggest that trends induced by diffusion differ drastically from observed felsic igneous trends.We do not believe that the principal arguments against FC in high-silica systems (unlikelihood of crystal settling; crystal-poor nature of tuffs) refute the reality of the chemical process, but rather emphasize the need for a better understanding of the physical mechanisms of crystal-liquid fractionation and eruption.     

A perspective on numerical analysis of the diffusion equation

The equation of transient groundwater motion is founded on the principle of mass conservation and can be mathematically described by the diffusion equation. Recently, powerful integral formulations have been developed for numerically solving the diffusion equation under complex conditions. In the literature, it is customary to formulate the integral equations by integrating point differential equations. Instead, in this paper, we shall employ a direct method of formulation, starting from the concepts of set and measure, the notion of partitions and the definition of set-averages.When the direct approach is applied to formulate the well-known finite element (FEM) equations, it is seen that the ‘Galerkin’ weighting function, which is mathematically treated as an artifice for weighting residuals, is but an appropriate spatial partition function. The logical framework of the direct approach is then applied to study the properties of ‘lumped’ and ‘consistent’ matrices arising in the use of the FEM. The lumped matrix, stemming naturally from the direct approach, seeks to conserve mass locally as well as globally, while the consistent matrix, which results only when the differential equation is integrated in a specific fashion, attempts only to preserve global mass balance.It is concluded that the direct approach is simple and complete and, in so far as the integral formulation is concerned, there is little to be gained in starting with the differential equation. Further, in formulating integral equations, it is common practice to evaluate only the time-dependent changes in the mass content of the system and ignore the evaluation of the mass content of the system at any given instant of time. In order to be complete in itself, a true integral approach should evaluate both the time-dependent changes in the mass content of the system as well as the instantaneous mass content at any given time.     

A diffusion approach to the statistical analysis of Kamchatka Seismicity

A diffusion approach was used to develop a statistical model of seismicity and to analyze Kamchatka earthquakes in order to detect features in the changes that are typical of random walk processes. We proposed a hypothesis of relationships among events and used an energy criterion to decompose the earth-quake catalog into a set of sequences, with each being a Brownian process with definite spatial, temporal, and energy scales. We constructed statistical distributions for these sequences over the number of their terms and total energies, as well as distributions of the sequences over distance, time, and flight times between events. We discuss non-local properties and memory effects in the random walk under different conditions.     

附加或不附加粘滞阻尼墙的RC框架试验与分析

本文阐述了附加或不附加粘滞阻尼墙的2个相同的RC框架模型振动台试验和理论分析的情况.这2个钢筋混凝土框架模型为3层1跨两开间,几何相似关系大致为1：2.将阻尼墙附加到一个RC框架模型当中,先后对附加或不附加阻尼墙的2个相同的RC框架模型进行振动台试验.试验结果表明,阻尼墙有效减小了框架模型的地震反应.对耗能框架模型和普通框架模型进行了弹性和弹塑性时程分析,计算结果和试验结果吻合良好.改变阻尼墙的参数进行分析,结果表明选取合适的阻尼墙参数,才能达到最好的耗能减振效果;适当减小层间位移较小处的阻尼墙参数,对减振效果影响很小而又能节省投资.     

3D Numerical modelling of flow divisions at open channel junctions with or without vegetation

The flow division at an open channel junction is affected by the inflow discharge and the downstream water depths of the junction. The growth of vegetation in a channel system is environmental friendly, but its effect on the flow in an open channel junction can be significant. In this work a 3D RANS (Reynolds Averaged Navier–Stokes equation) model has been implemented to investigate the flow phenomena in channel junctions with or without vegetation. The model is first validated by two cases: flow in an open channel T-junction without vegetation, and flow in a single open channel with vegetation. The model is then applied to simulate flow in an open channel T-junction with varying width ratio and vegetation density of the branch channel. The results quantitatively predict the trend of increasing flow in the branch channel with the increase in branch channel width and/or the decrease in vegetation density. The overall energy loss coefficient of the system, however, decreases with the amount of flow in the branch channel.     

Shaking table test and numerical analysis of single-layer reticulated domes with or without three-dimensional isolation bearing

Bulletin of Earthquake Engineering - Single-layer reticulated domes with high capacity and attractive shapes are widely used in many modern facilities, ranging from industrial architecture to...     

Stiffness and cyclic deformation capacity of circular RC columns with or without lap-splices and FRP wrapping

Mechanics-based models are developed for the moment, the curvature and the chord rotation at yielding of circular concrete columns or piers, their secant stiffness to the yield point and the ultimate curvature and flexure-controlled ultimate chord rotation in cyclic loading. The strain criteria for yielding or ultimate are calibrated on the basis of over four hundred test results. Besides the model for the secant-to-yield-point stiffness which is in terms of the yield moment and chord rotation, an empirical one, independent of the vertical reinforcement, is fitted to the data. The ultimate chord rotation is obtained from a plastic hinge model employing a plastic hinge length, the yield and the ultimate curvatures of the end section and the fixed-end rotation due to slippage of bars from their anchorage zone beyond the column length. All models are extended to columns the vertical bars of which are lap-spliced within the plastic hinge and to columns with FRP wrapping and continuous or lap-spliced vertical bars. The comprehensive portfolio of expressions proposed for the deformation properties of circular columns is fully consistent across the various situations of continuous or lap-spliced bars, with or without FRP wrapping, and with models developed by the authors from much larger databases of rectangular columns in similar situations; the aspects specific to circular sections are limited to the mechanics-based section analysis for moment and curvature, a purely empirical coefficient for the secant-to-yield-point stiffness and the empirical plastic hinge length.     

用广义协调元分析复合式多层无孔和开孔矩形薄板的振动

复合式多层无孔和开孔矩形薄板是桥梁结构和建筑等结构中的最重要的组成部分。当研究它们的振动问题时,用解析法求解自振频率十分困难,而采用通用的有限元法求解自由度数目多,收敛也比较慢。本文利用三角形薄板广义协调元分析了复合式多层四边简支、四边固定无孔和开孔矩形薄板的自由振动,求出了前几阶频率系数,其结果与用ANSYS软件算出的结果基本接近,当为单层无孔和开孔板时,与文献[8]的结果完全相同,且与文献[10]的解析解吻合较好,证明了本文理论推导及程序编制的正确性,表明广义协调元与有限元相比具有自由度少、精度高、程序简便以及收敛快等优点。     

A new method for the analytical solution of a degenerate diffusion equation

Certain nonlinear diffusion equations of degenerate parabolic type display a finite speed of propagation of disturbances. This mathematical behavior can be used to describe a wide range of nonlinear phenomena such as the penetration distance of a thermal layer, the boundary of a reaction zone, or a wetting front in unsaturated soil moisture flow. However, there are two main difficulties in obtaining solutions to problems of this class. One is that the location of the interface is not known a priori and must be discovered during the analysis. The other is the fact that the differential equation is singular in the neighborhood of the interface. The solution technique developed and presented in this work overcomes these difficulties by extracting a local solution of the differential equation in the neighborhood of the diffusing front. One profound result is the discovery that the velocity of the front is entirely controlled by the first term of the spectral series expansion. Also, by capturing the critical behavior of the solution in the region of the singularity and incorporating the behavior as a dominant factor, the series expansion is provided a means for very rapid convergence. The versatility of the solution technique is demonstrated by solving various boundary value problems covering a broad range of interest and the solutions are tested against previously published results.     

A three-dimensional numerical model of advection and diffusion of urban source pollutants

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A simple method for the determination of ionic diffusion coefficients in flooded soils

Soil cores from river marginal wetlands from the Torridge and Severn catchments in the UK were collected to study rates of soil denitrification at different sites and at two stations (levee and backplain depression) at the river margin. Half the cores were sterilized prior to flooding to destroy the denitrifying bacteria. After flooding and equilibration, monitoring the concentration of amended nitrate in the supernatant of the sterile cores over a period of 7 days provided a simple procedure for the estimation of the diffusion coefficient of the nitrate ion in the flooded soils. An expression was developed that permitted this diffusion coefficient to be extracted from the slope of a plot of supernatant concentration versus (time)^1/2. The values obtained, at 15 °C, varied from 2·4 to 6·8 × 10^?10m²s^?1. Sterile cores are usually treated as controls in denitrification experiments; this work develops a procedure whereby they may yield useful soil process information. Copyright © 2001 John Wiley & Sons, Ltd.     

A method for detecting the diffusion of silver iodide particles in the atmosphere

Summary A technique is described which allows the study of the concentration of silver-iodide particles produced by a ground generator. It consists of marking these particles with Iodine 131, then filtering the air at the required places with air-borne filters. The iodine is extracted chemically, concentrated in a very small silver iodide disc which is then placed upon a nulcear emulsion. After two weeks the activity is measured by electron track counting. Limitations of the method are given.The paper has been published in extenso in the «Zeitschrift für angewandte Mathematik and Physik» (ZAMP), XIa, p. 375, 1958.     

A diffusion approximation for a network of reservoirs with power law release rule

A diffusion approximation for a network of continuous time reservoirs with power law release rules is examined. Under a mild assumption on the inflow processes, we show that for physically reasonable values of the power law constants, the system of processes converges to a multi-dimensional Gaussian diffusion process. We also illustrate how the limiting Gaussian process may be used to compute approximations to the original system of reservoirs. In addition, we study the quality of our approximations by comparing them to results obtained by simulations of the original watershed model. The simulations offer support for the use of the approximation developed here.     

A modification of the dynamic method for determining the diffusion coefficient of aerosols

Summary The modification of the dynamic method suggested permits determining the diffusion coefficient of an aerosol from two concentration measurements (Z _v ) at the exit of a diffusion battery with different air-flows instead of measuring the concentration (Z) at the entrance and that (Z _v ) at the exit as originally employed.

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Zusammenfassung Die vorgeschlagene Modifikation der dynamischen Methode gestattet die Bestimmung des Diffusionskoeffizienten eines Aerosols aus zwei Konzentrationsmessungen (Z _v ) am Ausgange der Diffusionbatterie mit verschiedenen Luftstromgeschwindigkeiten anstatt der Messung der Konzentrationen am Eingang (Z) und Ausgang (Z _v ), wie in der ursprünglichen, Methode benützt.