bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic Rhodium(I)/Bisphosphane Complex‐Catalyzed Isomerization of Secondary Propargylic Alcohols to α,β‐Enones
Authors: Tanaka Ken , Shoji Takeaki , Hirano Masao 
Published: March 2007

AbstractWe have determined that hydrogenated cationic Rh(I)/bisphosphane complexes are highly active catalysts for the isomerization of secondary propargylic alcohols to α,β‐enones. A kinetic resolution of secondary propargylic alcohols proceeded with moderate selectivity with [Rh((R)‐BINAP)]OTf as a catalyst. Mechanistic studies revealed that the isomerization proceeds through intramolecular 1,3‐ and 1,2‐hydrogen migration pathways. The isomerization of propargylic diol derivatives was also investigated, which revealed that 1,4‐diketones, furans, and α,β‐enones were obtained from 2‐butyn‐1,4‐diol, 1‐methoxy‐2‐butyn‐4‐ol, and 1‐acetoxy‐2‐butyn‐4‐ol derivatives, respectively. Furthermore, chemoselectivity of the isomerization of an acetylenic diol was investigated, and preferential oxidation of a propargylic hydroxy group was observed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Speciation and Environmental Fate of Chromium in Rivers Contaminated with Tannery Effluents
Authors: Dominik J. , Vignati D. A. L. , Koukal B. , Pereira de Abreu M.‐H. , Kottelat R. , Szalinska E. , Baś B. , Bobrowski A. 
Published: March 2007

AbstractRedox and size speciation of chromium in rivers contaminated with tannery wastewater was carried out to provide insight into its transport and removal mechanisms. Total chromium was determined with Inductively Coupled Plasma‐Mass Spectrometry and Cr (VI) with Catalytic Adsorption Stripping Voltammetry. For the size speciation, particles were retained with a cartridge filter (cut‐off 1.2 μm) and the total filterable fraction was further fractionated with Tangential Flow Filtration to determine the concentrations of chromium associated with the High Molecular Weight Colloidal (HMWC), Low Molecular Weight Colloidal (LMWC) and Truly Dissolved (TD) fractions. Two fluvial systems of similar sizes, but located in contrasting climatic zones, were selected for comparison: the Sebou‐Fez system in Morocco and Dunajec River‐Czorsztyn Reservoir system in Poland. Particulate Cr dominated in the Sebou‐Fez system (about 90 %); while in the Dunajec‐Czorsztyn system, it represented only 17–53 % of the total chromium in raw water. Still, the partition coefficients [Kd] were of the same magnitude. Chromium (III) was the only form detected in Sebou‐Fez, whereas in Dunajec‐Czorsztyn Cr (VI) was also present with its proportion increasing downstream from the input of tannery wastewater due to the preferential removal of Cr (III). In the filtered water in Morocco a large fraction of Cr occurred in the HMWC fraction (50–70 %) at the two most contaminated sites, while the LMWC and TD forms prevailed at the non‐contaminated sites in the Sebou River. At a very high concentration, in the water in the proximity of tanneries (well above the theoretical saturation level) Cr precipitated as polynuclear Cr‐hydroxide. In Dunajec‐Czorsztyn, the partition of Cr (III) was approximately equal between the HMWC, LMWC and TD fractions, in contrast to Cr (VI) which occurred almost exclusively in the TD fraction. In both systems, Cr (III) was rapidly removed from the water to the sediments. The confluence of the Sebou with the Fez and the Czorsztyn reservoir trapped efficiently Cr (III) preventing its spreading over long distances. Cr (VI) showed conservative behavior and bypassed the Czorsztyn Reservoir. This study provides a first set of data on the partitioning of Cr (III) and Cr (VI) between the particulate, the colloidal and truly dissolved fractions in fluvial systems contaminated with tannery effluents. It also suggests that, in these systems, truly dissolved Cr (III) can be adequately modeled from the total filterable concentrations.
Discrete crack modelling for dynamically loaded, unreinforced concrete structures
Authors: Skrikerud Petter E. , Bachmann Hugo 
Published: March 2007

AbstractThe dynamic response of unreinforced concrete structures is studied taking account of initiation, extension, closing and reopening of so‐called discrete cracks. The computational procedure is based on the finite‐element method and is at present restricted to two‐dimensional situations. The discrete cracks are simulated by separation of originally adjacent finite elements. An equivalent tensile‐strength criterion is used for the initiation and extension of the cracks which are assumed to propagate perpendicularly to the principal tensile stress. If this direction does not coincide with the interelement boundaries of the finite‐element mesh, the latter is automatically altered. Between elements being separated by a crack special ‘crack elements’ are introduced, which take account of the stress transfer by aggregate interlock. The equations of motion are integrated numerically using an explicit formulation. The procedures outlined are demonstrated on a simplified cross‐section of a concrete gravity dam subjected to horizontal earthquake excitation.
Steady‐state harmonic response of a rigid plate bearing on a liquid‐saturated poroelastic halfspace
Authors: Halpern Marc R. , Christiano Paul 
Published: March 2007

AbstractSoil–structure interaction problems are typically modelled by assuming subgrade behaviour to be either elastic or viscoelastic. Herein, compliance functions that may be used to solve soil–structure interaction problems are evaluated by treating the subgrade as a liquid‐saturated poroelastic material whose behaviour is governed by Biot's theory.The compliances are evaluated for the harmonic rocking and vertical motions of rigid permeable and impermeable plates bearing on a poroelastic halfspace. Comparisons are made with elastic solutions which assume the subgrade to be either completely drained or undrained. Also, solid and fluid contact stresses are reported for the poroelastic case and compared to the solid contact stresses for the elastic cases.
A mixed method for transient analysis of soil–structure interaction under SH‐motion
Authors: Eilouch M. N. Alyagshi , Sandhu R. S. 
Published: March 2007

AbstractA Fourier transform approach is applied to the transient analysis of dynamic soil–structure interaction under SH‐motion. The governing equations are formulated in the frequency domain using a Finite Element–Boundary Element (FE–BE) coupling method. After solving the transformed problem, the transient solution is obtained using the discrete inverse Fourier transform with a fast Fourier transform algorithm. Two examples are presented in order to show the numerical performance of the proposed technique.
Hybrid modelling of a single‐layer half‐space system in SOIL–structure interaction
Authors: Tzong Tsair‐Jyh , Penzien Joseph 
Published: March 2007

AbstractA hybrid model is applied to two‐dimensional soil–structure interaction problems for the case of a single layer on a halfspace. A continuous impedance function along a semi‐cylindrical interface separating the near and far fields is proposed to simulate the radiation of energy and the energy reflection due to the layer of soil. This function as determined by system identification, together with a near‐field finite element system, provides a solution for the dynamic analysis of any type of structure.
Pipeline response to random ground motion by discrete model
Authors: Datta T. K. , Mashaly E. A. 
Published: March 2007

AbstractThe response of buried pipelines to random excitation by earthquake forces is obtained using a lumped mass model. The earthquake is considered as a stationary random process characterized by a power spectral density function (PSDF). The cross spectral density function between two random inputs along the length of the pipe is defined with the help of the local earthquake PSDF which is the same for all points, and a frequency dependent exponentially decaying (with distance) function. Soil resistance to dynamic excitation along the pipelength is obtained in an approximate manner with the help of frequency independent impedance functions derived from half‐space analysis and Mindlin's static stresses within the soil due to point loads. The proposed method has the advantage that it can take into consideration the cross terms in soil stiffness and damping matrices and can consider any boundary condition that needs to be satisfied at the ends of the pipe. A parametric study is also made to show the influence of cross terms in the soil stiffness and damping matrices on the response of the pipe.
Steady‐state and transient responses of non‐classically damped linear systems
Authors: Ventura Carlos E. , Veletsos Anestis S. 
Published: March 2007

AbstractA recently proposed procedure for interrelating the steady‐state and transient responses of multi‐degree‐of‐freedom, classically damped linear systems is extended to non‐classically damped systems. The extension is formulated for baseexcited systems, and it is illustrated by simple examples.
Mode‐superposition methods in dynamic analysis of classically and non‐classically damped linear systems
Authors: Borino G. , Muscolino G. 
Published: March 2007

AbstractMode‐superposition analysis is an efficient tool for the evaluation of the response of linear systems subjected to dynamic agencies. Two well‐known mode‐superposition methods are available in the literature, the mode‐displacement method and the mode‐acceleration method. Within this frame a method is proposed called a dynamic correction method which evaluates the structural response as the sum of a pseudostatic response, which is the particular solution of the differential equations, and a dynamic correction evaluated using a reduced number of natural modes.The greater accuracy of the proposed method with respect to the other methods is evidenced through extensive numerical tests, for classically and non‐classically damped systems.
Damping in tall buildings—a mechanism and a predictor
Authors: Jeary A. P. 
Published: March 2007

AbstractOnly when the data base is of sufficient quality can a theoretical model of any process be justified. Such a data base has recently been assembled in the field of damping in tall buildings. It is now possible to specify a damping value appropriate to a particular building vibrating at a specified amplitude which is well correlated with values which are measured in practice. The mechanism on which this predictor is based suggests that the predictor will be applicable to other types of structure as well. As yet the data base for these other structures does not exist, but some circumstantial evidence is encouraging.
Optimum design and earthquake‐response constrained design of elastic shear buildings
Authors: Nakamura Tsuneyoshi , Yamane Takashi 
Published: March 2007

AbstractThe necessary and sufficient conditions for global optimality and the closed form solution are derived for a problem of minimizing a weighted sum of storey stiffnesses of a shear building subject to a fundamental frequency constraint. A set of higher frequency formulae is derived for optimally designed shear buildings with equal masses. It is shown that, if the weight coefficients are regarded as parameters for adjustment, the distribution of the SRSS estimates of the maximum interstorey drifts can be adjusted so as to coincide with a specified one. The base shear–fundamental period formulae and the base shear–design drift formulae are derived semi‐analytically for shear buildings with equal masses on the basis of the optimum design formulae and the SRSS estimates of the maximum interstorey drifts. Some numerical examples are presented in order to illustrate the validity of the proposed method of earthquake‐response constrained design.
Response of a rigid foundation to a spatially random ground motion
Authors: Luco J. E. , Wong H. L. 
Published: March 2007

AbstractA method to obtain the dynamic response of an extended rigid foundation supported on an elastic half‐space when subjected to a spatially varying ground motion including both random and deterministic effects is presented. The method relies on an integral representation of the response of the foundation in terms of the free‐field ground motion. Numerical results for a rigid square foundation and for a ground motion characterized by a particular spatial coherence function are described. The results obtained indicate that the spatial randomness of the ground motion produces effects similar to the deterministic effects of wave passage including reduction of the translational components of the response at high frequencies and creation of rocking and torsional response components. The possibility of defining an effective apparent horizontal velocity which produces effects equivalent to those from a given spatial randomness is explored.
Response of a circular foundation on a uniform half‐space to elastic waves
Authors: Luco J. E. , Mita A. 
Published: March 2007

AbstractAn alternative technique to obtain the dynamic response of a massless rigid circular foundation resting on a uniform elastic half‐space when subjected to harmonic plane waves is presented. The technique relies on the use of an integral representation involving the free‐field ground motion and the contact tractions obtained in the course of calculating the dynamic force–displacement relationship of the foundation for external forces. Tables listing the translational and rotational components of the response of the foundation for non‐vertically incident SH, P, SV and Rayleigh waves are presented.
Floor response spectra with structure–equipment interaction effects by a mode synthesis approach
Authors: Suarez Luis E. , Singh M. P. 
Published: March 2007

AbstractA mode synthesis‐based direct approach is presented to calculate seismic response of equipment supported on structures. The approach incorporates the effect of the dynamic interaction between the equipment and the supporting structure. The modal properties of the combined structure–equipment system are obtained by synthesizing the modal properties of the individual structures. The seismic input defined in terms of smoothed ground response spectra can be directly utilized in this approach. Both heavy and light equipment can be considered by the approach equally effectively. Numerical examples demonstrating the effectiveness of the proposed approach are presented.
The non‐linear seismic response of AGR core graphite brick slices—correlation of experimental and analytical results
Authors: Ahmed Khalid , Stojko Stefan 
Published: March 2007

AbstractIt is a requirement for all future nuclear stations in the U.K. that they can be shut down safely in the event of an earthquake.The AGR reactor core structures have been mathematically modelled using non‐linear techniques which are implemented in the three‐dimensional computer code AGRCOR. Experimental verification of the code has already been determined for a simple one‐dimensional row of graphite brick slices.This paper discusses the correlation of experimental results with analytical predictions for the dynamic response of a two‐dimensional array of 18 graphite brick slices. The moving structure was excited in a single axis by a common rigid restraint structure in either a sine sweep or dwell mode at constant acceleration. In the paper, descriptions are given of (1) the numerical method; (2) the initial theoretical validation of AGRCOR; (3) the analytical and experimental models; (4) statistical methods used for correlation of results; and (5) the sensitivity of various parameters which control the response of the structure.The comparisons of experimental absolute brick velocities and interbrick shear forces with the analytical predictions were generally in good agreement. Also the resonant frequencies and instability regions of the brick responses were determined both experimentally and analytically.
Seismic response evaluation of Meloland Road Overpass using 1979 imperial Valley earthquake records
Authors: Werner S. D. , Beck J. L. , Levine M. B. 
Published: March 2007

AbstractDuring the 1979 Imperial Valley earthquake, an array of 26 strong‐motion accelerometers produced records for the Meloland Road Overpass, a two‐span reinforced concrete bridge structure located only 0.5 km away from the causative fault for this earthquake event. This paper describes the application of a new system identification methodology to the array of strong‐motion measurements, in order to assess seismic response characteristics of this bridge. Results of this application show that (1) linear models provide an excellent fit to the measured motions of the bridge, despite the fact that it was subjected to very strong shaking; (2) the transverse response of the structure is controlled by its abutment motions, with no significant dynamic amplification in the deck; and (3) the vertical response of the bridge deck at the midlength of its spans is dominated by a single vertical translational mode whereas, above the central pier, the deck's vertical response is most affected by the vertical motions of the pier base and by torsion of the deck. Also, systematic estimates of modal damping ratios and qualitative assessments of states of stress developed in the bridge during the earthquake are provided.
General dynamic‐stiffness matrix of a timoshenko beam for transverse vibrations
Authors: Chen Yung‐Hsiang 
Published: March 2007

AbstractThe general dynamic‐stiffness matrix of a Timoshenko beam for transverse vibrations is presented in this paper. All the effects of rotary inertia of the mass, shear distortion, structural damping, axial force, elastic‐spring and dashpot foundation are taken into account in the formulation. As a consequence, the deflection function of the beam vibration is in complex form, and the nature of the beam vibration and the corresponding dynamic stiffnesses of the beam are characterized by general complex wave numbers. The dynamic‐stiffness matrix for any special case can be derived easily from the general formula, which may be used directly in standard structural analysis.
The coupling effect of axial motion and joint mass on the lateral vibrations of a rigid‐jointed triangular frame
Authors: Kounadis A. N. , Meskouris K. 
Published: March 2007

AbstractIn this investigation, the coupling effects of the axial motion and other parameters on the bending eigenfrequencies and eigenmodes of laterally vibrating frames are re‐examined. To this end an energy variational approach is performed on a rigid‐jointed triangular frame, whose joint mass is eccentrically located with respect to its theoretical position. The governing partial differential equations subject to the appropriate boundary conditions are very conveniently formulated and successfully solved in a closed form by using generalized functions and Laplace transforms. Contrary to the usual assumptions of the standard dynamic analysis of continuous systems, herein the effect of axial contraction and extension is accounted for when establishing the translational kinematic boundary conditions. This may lead to considerable discrepancies that reveal the decisive role of the axial motion effect on the dynamic response of framed structures. Such discrepancies are clearly confirmed through a thorough numerical discussion of the governing parameters: joint mass and its rotatory inertia, joint angle, positioning of the mass, slenderness ratios, stiffness and length ratios.
Code design provisions for torsionally coupled buildings on elastic foundation
Authors: Chandler A. M. , Hutchinson G. L. 
Published: March 2007

AbstractThe effectiveness of the design recommendations made by various major building codes to account for torsional coupling effects is evaluated with respect to the parametric responses to earthquake ground motion of a simple single‐storey asymmetric building model supported on an elastic foundation. The objectives are to determine the extent to which the response trends observed in previous studies of asymmetric rigidly based buildings are affected by changes in the flexibility of the foundation medium and to comment on and suggest necessary amendments to the design recommendations in order that suitable allowance be made for the resultant changes in the magnitude of torsional coupling effects. It is concluded that whilst the qualitative effects of torsional coupling are not affected by soil–structure interaction, their magnitude depends significantly on the frequency content of the free‐field motion. The response to the El Centro earthquake record is conservatively accounted for by assuming the structure to be supported on a rigid foundation. An allowance for increased response effects due to soil–structure interaction is suggested for incorporation in the torsional design recommendations when European earthquake records are employed.
Vertical vibration of three‐dimensional rigid foundations on layered media
Authors: Chow Y. K. 
Published: March 2007

AbstractA numerical method of analysis is presented for the determination of the steady‐state vertical vibration of rigid foundations with arbitrary three‐dimensional geometries resting on the surface of a layered soil medium. The method utilizes the flexibility concept applied to steady‐state periodic problems and it is solved in the frequency domain. The accuracy of the method is verified by comparison with several published solutions for massless, smooth rigid rectangular foundations on a homogeneous, isotropic elastic half‐space. Parametric solutions are presented to study the dynamic behaviour of massless, smooth rigid rectangular foundations on a homogeneous, elastic stratum.
Use of seismic data from similar regions
Authors: Rosenblueth Emilio , Ordaz Mario 
Published: March 2007

AbstractAttention is first focused on the probability distributions of the exceedance rates of given earthquake magnitudes when the generation process is idealized as Poisson. But data on significant disturbances are always scarce. Local‐seismicity assessment is hence guided by information from tectonically similar areas, but ordinarily the guidance is intuitive. Bayesian statistics constitute the tool to do this rationally. Two more alternatives are presented and illustrated here. The approach is extended to a generating process that includes the Poisson as a special case.
The soft‐output principle—reminiscences and new developments
Authors: Hoeher Peter A. , Robertson Patrick , Offer Elke , Woerz Thomas 
Published: March 2007

AbstractA major breakthrough in digital communications was the provisioning of ‘soft’ outputs at each processing stage, with appropriate capabilities to use this as soft inputs in the next processing stage. This allowed for much more performant receivers especially in difficult mobile radio channel conditions, and set the stage for iterative processing. This article will outline the development of soft output algorithms over the last two decades along with associated state‐of‐the‐art applications and conclude with an outlook towards novel applications of the soft principle. Copyright © 2007 John Wiley & Sons, Ltd.