bluuebunny/crossref_metadata_2025 huggingface dataset:
Corporate social reporting: segmentation and characterization of Spanish companies
Authors: García‐Sánchez Isabel Ma
Published: April 2007

This study establishes a new methodology in the analysis of the corporate social information disclosed by companies, since the objective pursued does not concentrate on showing the amount of information issued by each one of the companies individually, but rather on grouping them, taking into consideration their similarity in content and in the characteristics of the information revealed.

Afterwards, those characteristics were identified that define or help determine membership in each segment or informative group. This shows that the similarity in the content and the characteristics of the information revealed is positively associated with larger‐sized companies that belong to certain sectors of business activity. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
On the Modelling of a Nonequilibrium Spherical Microwave Discharge at Atmospheric Pressure
Authors: Rafatov I. R.
Published: April 2007

The work presents results of calculation of a spherical microwave discharge characteristics in an argon at atmospheric pressure against the external parameters (the mode, frequency and power of the applied electromagnetic field and the size of the discharge chamber). Model assumes a thermal and ionization non‐equilibrium of discharge plasma and takes into account first three modes of incident electromagnetic waves. Calculation results are compared with the results for the ionization equilibrium model. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermally Conducting Partially Ionized Plasma in a Variable Magnetic Field
Authors: Shaikh S. , Khan A. , Bhatia P. K.
Published: April 2007

An infinitely extending homogenous partially ionized plasma endowed with several physical mechanisms and permeated by a variable magnetic field is considered. The combined effect of these parameters, namely, Hall currents, finite conductivity, ion viscosity, collision with neutrals and thermal conductivity on the gravitational instability of the plasma is studied. It is found that the several mechanisms play different physical roles in the perturbed problem. Jeans' Criterion is analyzed in the framework of Tsallis' statistics for possible modifications due to the presence of nonextensive effects. A simple generalization of the Jeans' criterion is obtained and the standard values are obtained in the limiting case q = 1, q being the nonextensive parameter. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Calculation of the Townsend Discharge Coefficients and the Paschen Curve Coefficients
Authors: Burm K. T. A. L.
Published: April 2007

The determination of Paschen curve coefficients A and B and the first and second Townsend coefficient are discussed for the creation of gas discharges from extraordinary gasses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma Profiles in a Cylindrical Helicon Discharge with Converging Magnetic Source Field
Authors: Grulke O. , Stark A. , Windisch T. , Zalach J. , Klinger T.
Published: April 2007

Detailed Langmuir probe measurements of the plasma density, plasma potential, and electron temperature in the cylindrical helicon device VINETA [C. M. Franck et al., Phys. Plasmas 9(8), 2002] are presented. The probe measurements cover the entire radial‐axial plane including the helicon antenna region. Two magnetic field configurations are compared: homogeneous magnetic field in the helicon antenna region and magnetic field gradient at the transition between the antenna and the discharge chamber. It is demonstrated that the converging magnetic field leads to the formation of steep plasma density and potential increase, which is strongly correlated with the position of the maximum field gradient. No electron heating detached from the helicon source is observed. The measurements strongly suggest that the plasma profiles are the direct result of volume reduction due to magnetic field convergence, which leads to the formation of a single sheath‐like layer in front of the helicon source. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Double Sheath at the Plasma‐Wall Boundary
Authors: Alterkop B. , Dubinova I. D. , Dubinov A. E. , Boxman R. L.
Published: April 2007

The relation between plasma parameters determining a steady‐state charged sheath at a plasma‐wall boundary was derived and analyzed using a fluid model, which accounted for inertia and partial pressure of both plasma components. The relation generalizes the well‐known Bohm criterion and, in particular, shows that a steadystate sheath may be formed in some cases where the Bohm criterion is not satisfied. Conditions allowing formation of a double sheath structure were formulated and analyzed. It was shown that the structure may be formed only if a) the generalized Bohm criterion is satisfied, and b) the Sagdeev potential has a minimum. The double sheath structure consists of two sub‐sheath of different polarity, which depends on the wall potential polarity and the relation between the plasma component temperatures and inertia. For positive wall potential, the sub‐sheath adjacent to the plasma (the sheath edge) is enriched by negative particles, and the sub‐sheath adjacent to the wall is enriched by positive particles, while the sub‐sheath polarities are reversed for negative wall potential. An analytical theory was formulated and illustrated by numerical solutions of the Poisson equation for special cases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystalline, Uniform‐Sized TiO2 Nanosphere Films by a Novel Plasma CVD Process at Atmospheric Pressure and Room Temperature
Authors: Zhu A.‐M. , Nie L.‐H. , Wu Q.‐H. , Zhang X.‐L. , Yang X.‐F. , Xu Y. , Shi C.
Published: April 2007

A novel plasma CVD process induced by diffuse coplanar surface discharges (DCSD) for TiO2 film fabrication at atmospheric pressure and room temperature is reported. Using this simple and low‐cost process, uniform‐sized nanosphere, crystalline TiO2 thin films (see figure) have been successfully fabricated.
Progression to impaired glucose regulation, diabetes and metabolic syndrome in Chinese women with a past history of gestational diabetes
Authors: Tam Wing Hung , Yang Xi Lin , Chan Juliana C. N. , Ko Gary T. C. , Tong Peter C. Y. , Ma Ronald C. W. , Cockram Clive S. , Sahota Daljit , Rogers Michael S.
Published: April 2007

Background

To examine the risk of developing impaired glucose regulation (IGR), diabetes mellitus (DM) and metabolic syndrome (MetS) in Chinese women with history of gestational diabetes.

Methods

203 Chinese women enrolled in a previous study were followed up at a median of 8 (range 7–10) years of whom 136 had normal glucose tolerance (NGT) and 68 had gestational diabetes mellitus (GDM) and gestational impaired glucose tolerance (GIGT).

Results

In women with a history of gestational diabetes (n = 4), GIGT (n = 63) and NGT (n = 136), 2 (50%), 19 (30.2%) and 21 (15.4%) developed IGR while 2 (50%), 4 (6.3%), 3 (2.2%) developed DM respectively. Most women developed IGR (86%, n = 36) or DM (78%, n = 7) were undiagnosed. MetS occurred in 16 (7.9%) women with similar rates between those with and those without a history of gestational diabetes (7.5% vs 8.1%; p = 0.85). History of gestational diabetes [OR: 3.8 (95% CI 1.9–7.8)] and body mass index (BMI) ≥ 23 kg/m2 [OR: 3.4 (95% CI 1.7–6.8)] at first antenatal visit were predictors for IGR or DM. Family history of DM [OR: 5.0 (95% CI 1.5–16.4)] and BMI ≥ 23 kg/m2 [OR: 28.3 (95% CI 3.6–223)] at first antenatal visit were predictors for MetS.

Conclusions

Chinese women with a history of gestational diabetes have a high risk of IGR or DM. Overweight at the first antenatal visit is a common risk factor for IGR, DM and MetS. A prior history of gestational diabetes was predictive of IGR and DM while a positive family history of DM was predictive of MetS. Copyright © 2007 John Wiley & Sons, Ltd.
Inhibition of NKG2D receptor function by antibody therapy attenuates transfer‐induced colitis in SCID mice
Authors: Kjellev Stine , Haase Claus , Lundsgaard Dorthe , Ursø Birgitte , Tornehave Ditte , Markholst Helle
Published: April 2007

A role for the activating NK‐receptor NKG2D has been indicated in several autoimmune diseases in humans and in animal models of type 1 diabetes and multiple sclerosis, and treatment with monoclonal antibodies to NKG2D attenuated disease severity in these models. In an adoptive transfer‐induced model of colitis, we found a significantly higher frequency of CD4+NKG2D+ cells in blood, mesenteric lymph nodes, colon, and spleen from colitic mice compared to BALB/c donor‐mice. We, therefore, wanted to study the effect of anti‐NKG2D antibody (CX5) treatment initiated either before onset of colitis, when the colitis was mild, or when severe colitis was established. CX5 treatment decreased the detectable levels of cell‐surface NKG2D and prophylactic administration of CX5 attenuated the development of colitis significantly, whereas a more moderate reduction in the severity of disease was observed after CX5 administration to mildly colitic animals. CX5 did not attenuate severe colitis. We conclude that the frequency of CD4+NKG2D+ cells increase during development of experimental colitis. NKG2D may play a role in the early stages of colitis in this model, since early administration of CX5 attenuated disease severity.
T1/ST2 expression on Th2 cells negatively regulates allergic pulmonary inflammation
Authors: Mangan Niamh E. , Dasvarma Ayan , McKenzie Andrew N. J. , Fallon Padraic G.
Published: April 2007

The transmembrane form of T1/ST2 (ST2) is a specific marker on murine Th2 cells that have been generated in vitro, or isolated from sites of allergic type 2 inflammation. Despite the association of ST2 with Th2 cells, to date no obligate role for ST2 in type 2 responses in vivo has been described. We have specifically addressed the role of ST2 on T cells by generation of ST2–/– mice crossed with ovalbumin (OVA) T cell receptor‐transgenic mice. OVA‐specific ST2–/– cells had normal cytokine responses to T cell activation after in vitro Th2 differentiation, but OVA stimulation of IL‐5 was increased. Transfer of OVA‐specific ST2–/– Th2 cells into BALB/c mice caused exacerbated pulmonary inflammation with occluded airways, elevated airway hyper‐responsiveness and increased susceptibility to methacholine challenge that was associated with mortalities of recipient mice. The increased pulmonary inflammation in OVA‐specific ST2–/– Th2 cell recipients was associated with selective differences in pulmonary levels of Th2 cytokines compared with OVA‐specific ST2+ Th2 cell recipients. Recipients of OVA‐specific ST2–/– Th2 cells had a significant increase in eosinophils and a significant reduction in F4/80hi macrophages in the lungs. This is the first demonstration of a role for ST2 expression on Th2 cells down‐regulating pulmonary inflammation. These data have major implications for the targeting of ST2 as a therapy for allergic airway disorders.
Synthesis, Structures and Optical Power Limiting of Some Transition Metal and Lanthanide Monoporphyrinate Complexes Containing Electron‐Rich Diphenylamino Substituents
Authors: Fu Shitao , Zhu Xunjin , Zhou Guijiang , Wong Wai‐Yeung , Ye Cheng , Wong Wai‐Kwok , Li Zaoying
Published: April 2007

Transition metal and lanthanide monoporphyrinate complexes based on 5,10,15,20‐tetrakis[p‐(diphenylamino)phenyl]‐21H,23H‐porphine (H2tdpapp) have been synthesized and characterized and the X‐ray crystal structures of the palladium and platinum analogues [M(tdpapp)] (M = Pd, Pt) determined. Experimental investigations of the nonlinear optical transmittance characteristics at 532 nm show that most of these new metalated porphyrinate complexes are excellent optical limiters with performances comparable or superior to those of the benchmark reverse saturable absorption dyes such as fullerene C60 and (phthalocyanine)metal complexes. The nonlinear optical measurements reveal that the optical‐limiting effects of porphyrins can be enhanced greatly by incorporation of lanthanide ions and covalent attachment of the electron‐donating diphenylamino moieties to the parent porphyrinate ring. The optical‐limiting thresholds for these lanthanide monoporphyrinate complexes range from 0.09 to 0.30 J cm–2 at 82 % linear transmittance, which makes them attractive candidates as optical‐limiting materials for the protection of various optical devices. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Effect of Protonation and Interaction with Anions on a Lead(II) Complex with a Lateral Macrobicycle Containing a Phenol Schiff‐Base Spacer (Eur. J. Inorg. Chem. 12/2007)
Authors: Esteban‐Gómez David , Platas‐Iglesias Carlos , Avecilla Fernando , de Blas Andrés , Rodríguez‐Blas Teresa
Published: April 2007

The cover picture shows a crown‐based lateral macrobicycle designed by our research group as a potential ligand for PbII complexation. Lead is recognized worldwide as a serious environmental pollutant, and although it is a natural component of soil, water and vegetation, anthropogenic emissions have contributed to the dramatic increase in its level in the environment. The removal of lead from the environment and biological systems is the aim of many research groups. In particular, we are interested in the design of PbII‐complexing agents based on crown frameworks. In this picture, the complexed PbII ion has been replaced by our beautiful but polluted blue planet. The cover picture symbolizes the need for innovative ideas to solve the problem of environmental lead pollution – one solution includes the design of selective complexing agents. Details are discussed in the article by A. de Blas, T. Rodr�guez‐Blas et al. on p. 1635 ff.
Solid Contact Micropipette Ion Selective Electrode for Potentiometric SECM
Authors: Gyetvai Gergely , Sundblom Sören , Nagy Lívia , Ivaska Ari , Nagy Géza
Published: April 2007

New solid contact ammonium micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of micropipette ISE‐s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions.
The generalized linear model and extensions: a review and some biological and environmental applications
Authors: Paul Sudhir , Saha Krishna K.
Published: April 2007

The generalized linear model (GLM) encompasses many discrete and continuous models and it is particularly useful for analyzing discrete data. However, in many real life applications, the full distributional assumption of the GLM cannot be justified. Further, the GLM cannot accommodate over‐dispersion in the data. Since the inception of the GLM by Nelder and Wedderburn (1972) a number of its extensions have been proposed in the literature for robust analysis of discrete data. The purpose of this paper is to critically review these extensions. Applications to over‐dispersed Poisson and binomial models are shown. Some simulations are conducted to compare, in terms of bias and efficiency, the estimates of mean and the dispersion parameters by different methods. Applications to some biological and environmental data are given. Copyright © 2007 John Wiley & Sons, Ltd.
Non‐linear response spectrum method for three‐dimensional structures
Authors: Sutharshana Saravanapavananthan , McGuire William
Published: April 2007

An approximate non‐linear response spectrum method for the analysis of three‐dimensional structures is presented. The non‐linear effects are taken into account by employing an equivalent linearization criterion along with inelastic spectra and geometric stiffness matrices. The linearization procedure replaces the inelastic system by an equivalent linear syste on a member‐by‐member basis and accounts for the frequency shift and change in damping. Rational procedures combining modal and spatial response maxima for three‐dimensional structures subject to multi‐component respone spectra are also discussed. The modal response spectrum predictions compare favourably with those obtained from die time‐history analyses.
The influence of highly stratified dissipative soil on ground motion
Authors: Xu P.‐C. , Mal A. K.
Published: April 2007

The influence of the depth and material properties of a sedimentary deposit on earthquake ground motion is examie through theoretical modelling. The strong stratification of a typical deposit is represented by a number of homogene layers of dissipative viscoelastic material. The motion is assumed to be produced by a line source. The calculations carried out by means of a recently developed theoretical technique. The near surface low velocity layers are found to has a very strong amplification effect on the ground motion at some frequencies. The widely used one dimensional approae for site effect evaluation is shown to be valid for smaller epicentral distances only. The deamplification effect of mate dissipation is shown to be extremely important in most cases.
Analysis of continuous buried pipelines for seismic wave effects
Authors: O'Rourke Michael J. , Hmadi Kamel El
Published: April 2007

An analysis procedure for seismic wave propagation effects on straight continuous buried pipelines is proposed. It shown that ground strain due to surface waves can be substantially larger than that due to body waves. An elastic model a buried pipeline surrounded by equivalent soil springs indicates that frictional slip between the pipeline and the surrounding soil springs is likely for high ground strains.

A method for estimating ground strain due to surface waves, based on data from the 1971 San Fernando earthquake, reviewed. An analysis procedure, which utilizes frictional forces near the soil‐pipeline interface, is proposed for surfae wave effects on straight buried continuous pipelines. The proposed procedure is illustrated with an example.
A subspace modal superposition method for non‐classically damped systems
Authors: Mau S. T.
Published: April 2007

For structures with non‐proportional damping, complex eigenvectors or mode shapes must be used in order to decoe the equations of motion. The resulting equations can then be solved in a systematic way. The necessity of solvie complex eigenvalue problem of a large system remains an obstacle for the practical application of the method. This stres utilizes the fact that in practice only a small number of the complex modes are needed. Therefore, these complex modes be approximated by a linear combination of a small number of the undamped modes, which can be obtained by established methods with less cost. An additional eigenvalue problem is then solved in a subspace with a much sm dimension to provide the best combination coefficient for each complex mode. The method of solution for the decoue equations is then carried over, using the approximate complex modes expressed in undamped mode shapes, to resue simple formulas for the time‐ and frequency‐domain solution. Thus, an efficient modal superposition method is develoe for non‐proportionally damped systems. The accuracy of this approximate method is studied through an example. Comparing the frequency response result using the approximate method with that using the exact complex modes, found that the error is negligible.
Horizontal impedances for radially inhomogeneous viscoelastic soil layers
Authors: Veletsos A. S. , Dotson K. W.
Published: April 2007

A study of the dynamic impedances of horizontally excited, radially inhomogeneous, infinite viscoelastic soil layers with a circular hole, and of piles embedded in a medium represented by such layers is made considering the shear modulus of the material to increase radially within a narrow annular boundary zone. Unlike a previous study in which the boundary zone was presumed to be massless, in the present study the inertia effects of this zone are taken into account. The impedances are evaluated over wide ranges of the parameters involved and the sensitivity of the results is assessed. The results are also compared with those obtained for similarly excited homogeneous layers and for vertically excited inhomogeneous layers. For purposes of analysis, the inhomogeneous boundary zone is represented by a series of concentric rings of constant properties, and the transfer matrix technique is used to evaluate the results. The analysis and the computer program used to implement it are applicable to layers of arbitrary radial variation of material properties.
Physical constraints in engineering seismic hazard analysis
Authors: Papastamatiou Dimitri , Sarma Sarada K.
Published: April 2007

In engineering seismic hazard probabilistic analysis, physical constraints are generally overlooked. We formulate such constraints for the general case of a site within an annular seismogenic zone. This configuration provides a first approximation of seismic hazard analysis within a broad zone undergoing crustal deformation; such zones are a common expression of continental tectonics. Applications are restricted to medium size earthquakes (Ms < 7). The formulation is applied to two cases reflecting the mid‐plate (case I) and plate boundary (case II) seismotectonic environments. It is found that, for a given strain rate and for an upper bound magnitude of 6 3/4, the extreme hazard in both the environments is the same but of different character. In the plate boundary example, it is associated with widespread ground deformation while in the mid‐plate example, it involves more intense ground motion. On the other hand, if the upper bound magnitude is 5 3/4, the extreme hazard is likely to be an order of magnitude less in case I than in case II. Moreover, when the extreme hazard is associated with singular conditions generated by a single fault, the assumption of a Poissonian process may not be safe for earthquake resistant design decisions.
Earthquake‐induced ground displacements
Authors: Ambraseys N. N. , Menu J. M.
Published: April 2007

The paper brings up to date and amplifies earlier work on earthquake‐induced ground displacements using near‐field strong‐motion records, improved processing procedures and a homogenizing treatment of the seismological parameters. A review of upper bound limits to seismic displacements is given and a predictive procedure is examined that allows the probabilistic assessment of the likelihood of exceedance of predicted displacements to be made in the near field of earthquakes in the magnitude range 6.6 to 7.3. Using a considerable number of unscaled ground motions obtained at source distances of less than half of the source dimensions, graphs and formulae are derived that allow the assessment of permanent displacements of foundations and slopes as a function of the critical acceleration ratio.
Simulation of risk‐consistent earthquake motion
Authors: Kameda Hiroyuki , Nojimaf Nobuoto
Published: April 2007

A method to combine probabilistic seismic hazard analysis and stochastic earthquake motion models is presented. A set of parameters characterizing stochastic earthquake motion models is determined on a consistent probabilistic basis. The method proposed herein consists of two steps. First, the ground motion intensity is determined in the context of the conventional hazard curve technique. Next, other ground motion parameters such as duration, predominant frequency and spectral shape parameters are determined as conditional means corresponding to the annual probability of exceedance for the ground motion intensity. Some example applications are presented.
Experimental and finite element studies of the forced vibration response of morrow point dam
Authors: Duron Ziyad H. , Hall John F.
Published: April 2007

Measured accelerations and water pressures obtained during a recent forced vibration test on a large thin arch dam at high water are compared to predictions from a finite element model for which water compressibility is both included and neglected. The numerical model is calibrated using the antisymmetric response data because they are only slightly affected by water compressibility; good agreement is obtained. In the effort to reproduce the symmetric response data, for which water compressibility plays a strong role, the calibrated model shows better correlation when water compressibility is included, but the agreement is still inadequate. A successful isolation of the fundamental water resonance from the experimental data shows significantly different features from those of the numerical water model, indicating possible inaccuracy in the assumed geometry and/or boundary conditions for the reservoir. Some other results at low water level are also included.
Advanced application of bem to wave barriers in multi‐layered three‐dimensional soil media
Authors: Banerjee P. K. , Ahmad S. , Chen K.
Published: April 2007

An advanced application of BEM to the problem of wave screening by barriers is described. The BEM formulation has been developed by utilizing advanced surface modelling, automatic (self‐adaptive) error control in the numerical integration. The soil is modelled as a layered, isotropic and linear elastic or viscoelastic medium. The results of the analysis have been compared with full scale test data.
Peak response of 2‐DOF uncoupled oscillator under two‐directional base motion
Authors: Slafak E. , Bendimerad M. F.
Published: April 2007

This paper investigates the peak response of a 2‐DOF uncoupled linear oscillator under arbitrarily oriented two‐component horizontal earthquake motion. Input data consist of 22 two‐component acceleration records from the magnitude 6.6, October 15, 1979 Imperial Valley earthquake. One‐directional response spectra for each principal direction of the oscillator, and two‐directional response spectra (amplitude of the peak resultant response and its direction with respect to principal directions) are calculated by considering all angles of incidence of the excitation. The results indicate that, for oscillators that are not too flexible (i.e. with natural frequencies greater than 0.8 Hz), the two‐directional peak response is controlled by the weaker direction of the oscillator. For flexible oscillators the two‐directional peak response is controlled by the direction whose natural frequency is closer to dominant ground motion frequencies. The results also show that when the two‐directional peak response is expressed as a weighted sum of one‐directional peak responses, the weighting factors are not constants, but functions of oscillator and dominant ground motion frequencies.
Simplified analysis of unanchored tanks
Authors: Peek R. , Jennings P. C.
Published: April 2007

Local uplift of the tank wall is perhaps the most important characteristic of the seismic behaviour of unanchored liquid storage tanks made out of steel. Such uplift is necessary, because unanchored tanks rely primarily on the weight of the liquid resting on an uplifted portion of the base plate to balance the overturning moments that occur during strong shaking. A simplified method of analysis for static lateral loads is developed, based on the assumption that the restraining action of the base plate can be modelled with equivalent, non‐linear springs. This assumption, together with a Fourier decomposition of the displacements, simplifies the problem to the extent that it can be solved on a personal computer. The solutions are compared with those from experiments and those from current U.S. design analysis methods.
Analysis of unanchored liquid storage tanks under lateral loads
Authors: Peek Ralf
Published: April 2007

Many liquid storage tanks consist of a steel cylindrical shell, which is welded to a base plate, but not fixed to the foundation. When such an unanchored tank is subjected to lateral loads due to earthquake induced hydrodynamic pressures in the liquid, the tank wall tends to uplift locally, pulling the base plate up with it. The contact problem of the partially uplifted base plate and its interaction with the the cylindrical shell is solved in this paper using the finite difference energy method, and a Fourier decomposition of the displacements in the circumferential direction. Non‐linearities due to contact, finite displacements and yield of the steel are included in the analysis. However, the equations for the shell are linearized. This uncouples the equations for the Fourier displacement coefficients in the cylindrical shell, and enables the degrees of freedom for the shell to be eliminated by static condensation at very little computational cost.

Comparing the analytical results to (for the most part existing) experimental results, produces good agreement in some cases and not so good in others. A number of effects that could give rise to such differences are discussed. In most cases they represent experimental conditions that are not known or modelled in the analysis. The analysis results are also compared to those from a simplified analysis in which the hold‐down action of the base plate is modelled by means of nonlinear Winkler springs.
Buckling and vibration analysis of flexible beams resting on an elastic half‐space
Authors: Karamanlidis Dimitrios , Prakash Vikas
Published: April 2007

The present paper deals with the buckling and vibration of prismatic beams resting on an elastic half‐space. The computational procedure developed herein utilizes the advantages of both an analytical approach and a finite element scheme. This is accomplished by deriving exact frequency and axial force dependent stiffness matrices using the analytical solutions of the governing differential equation as ‘shape functions’. The major advantages of the proposed approach over previous ones are pointed out and discussed in detail. Numerical results demonstrating the performance of the proposed method are presented in the final part of the paper.
A plane strain soil‐structure interaction model
Authors: Dangla P.
Published: April 2007

A plane strain model for dynamic soil‐structure interaction problems under harmonic state is presented. The boundary element method is used to study the response of a homogeneous isotropic linear elastic soil. The far field displacement at the free surface is approximated by an outgoing Rayleigh wave. The finite element method is used to describe the response of the building, of the foundation and possibly of a finite part of the inhomogeneous non‐linear soil. Two coupling procedures are described. The model is applied to a problem previously studied in the antiplane case. Incident P, SV and Rayleigh waves are considered. The results show an amplification and an attenuation of the structure motion with frequency when incident Rayleigh waves and P, SV body waves are respectively considered.
Boundary element reservoir model for seismic analysis of gravity dams
Authors: Humar J. L. , Jablonski A. M.
Published: April 2007

The boundary element method has been successfully applied in the past to the analysis of hydrodynamic forces in two‐ and three‐dimensional finite water reservoirs subjected to seismic ground motions. In extending the method to an infinite reservoir, the loss of energy due to pressure waves moving away towards infinity must be taken into account. In addition, for both finite and infinite reservoirs, energy is lost owing to partial absorption of the waves incident on a flexible bottom consisting of alluvial deposits. This paper presents the results of more recent research on the application of the boundary element method to the analysis of 2D reservoir vibration. Two different formulations are used: a constant boundary element formulation and a linear boundary element formulation. Special boundary conditions to treat infinite radiation and foundation damping have been incorporated in both formulations. Numerical results have been obtained for each of the two alternative formulations and compared against each other as well as with classical solutions and results obtained by other researchers.
Stiffness identification of two‐ and three‐dimensional frames
Authors: Torkamani Morteza A. M. , Ahmadi Ahmad K.
Published: April 2007

Four widely used structural system identification methods are presented. Based on Bayesian estimation theory, two new formulae and their derivations are shown. Time domain responses of two frames when subjected to the ground motion of the El Centro earthquake are computed then transformed to the frequency domain. Frequencies and mode shapes of frames are extracted from Fourier spectra. Using these frequencies and mode shapes, a parametric study is conducted, and the system identification methods are compared and discussed. The importance of a prior analytical model on the rate of convergence of the revised parameters is investigated. Recommendations are given regarding the feasibility of each method for more accurate estimation. A model suitable for parameter identification of three‐dimensional frames is presented. This model, with different identification methods, is used to estimate the parameters of a two‐storey frame.
Stiffness identification of a tall building during construction period using ambient tests
Authors: Torkamani Morteza A. M. , Ahmadi Ahmad K.
Published: April 2007

Ambient response measurements were made on an eighteen‐storey building at three different stages of construction to detect any changes in the frequencies, mode shapes and stiffness with construction. The first nine frequencies and corresponding mode shapes for each stage of construction are found. A comparison is made among these mode shapes and frequencies and with the mode shapes and frequencies of an analytical model incorporating beams, columns, shear walls, panels and diagonal elements. The added effects, on frequencies and mode shapes, of non‐structural elements such as stairs, elevators, claddings and partition walls are studied. Using Improved Statistical Structural Identification, an attempt is made to study the stiffening effect of non‐structural elements by updating the stiffness matrix of the building.
A note on non‐stationary stochastic response and strong motion duration
Authors: Zembaty Zbigniew
Published: April 2007

An analysis of the influence of strong motion duration on the response spectra is presented. The analysis is based on the concept of evolutionary power spectral density and first passage estimations for non‐stationary random vibrations. To compare the response for different durations the criteria of constant Arias intensity and constant excitation level have been applied. The paper presents a numerical analysis of the effect of strong motion duration on various response statistics for a linear oscillator. Results indicate a decrease of peak response and first passage probability with increasing strong motion duration for constant Arias intensity.
The effect of earthquake duration on the damage of structures
Authors: Jeong Garrett D. , Iwan Wilfred D.
Published: April 2007

This paper presents a theoretical analysis of the effect of duration on the damage of structures subjected to earthquakes. The earthquake excitation is modelled by a non‐stationary random process whose response spectrum is probabilistically consistent with a design response spectrum specified independently of the duration. Damage is assumed to accumulate with the cyclic application of large strains in the structural members. Two types of structure are examined: one representative of a steel structure and the other reprsentative of a reinforced concrete structure. The level of expected damage is found to be a strong function of both the ductility of the response and the duration of the excitation. Results are presented for systems with linear stiffness and a particular form of softening behaviour.
Optimum strong‐motion array geometry for source inversion
Authors: Iida Masahiro , Miyatake Takashi , Shimazaki Kunihiko
Published: April 2007

Optimum strong‐motion array geometry for source inversion is quantitatively determined for each of three types of earthquake faults: strike—slip, dip‐slip and offshore subduction thrust. The estimation is done by using the source inversion method1,2 previously developed and based on Wolberg's prediction analysis.3 Only the far‐field S waves are taken into account in source inversion; we test only the ability to estimate seismic moments of subfault elements. A comparison of the optimum array geometries obtained in this study with the ones proposed on the basis of an empirical judgment at the 1978 International Workshop on Strong‐Motion Earthquake Instrument Arrays4 shows that the Workshop geometries are not the best ones as far as source studies are concerned. The most preferable array involves two different kinds of stations regardless of the target fault type: stations close to the fault and aligned parallel to its strike, and stations surrounding the fault area with good azimuthal coverage. The former stations resolve the later stage of the rupturing process while the latter stations resolve the earlier stage.
Vibration suppression of structures
Authors: Ebrahimi N. D.
Published: April 2007

A procedure for vibration suppression of elastic structures and systems is introduced in this paper. First, the equations of the response of the system to external forces, based on a discretized linear model, are developed. Next, the vibration suppression is formulated as a minimization problem with control (external) forces as unknowns. Then, the optimality condition is applied to this problem and a set of linear simultaneous equations is obtained for the unknown forces. The scheme is applied to a number of simple examples for illustration. The results show that the procedure is very effective and, at the same time, very flexible compared to methods that are based on continuous models (partial differential equations). The actual (hardware) implementation can be achieved by means of either passive absorbers or active forces (actuators).
A comparative study of performances of various base isolation systems, part I: Shear beam structures
Authors: Su Lin , Ahmadi Goodarz , Tadjbakhsh Iradj G.
Published: April 2007

A comparative study of performances of different base isolators for shear beam type structures is carried out. Several leading base isolation systems, including the laminated rubber bearing with and without lead plug, the resilient‐friction base isolator with and without sliding upper plate, and the EDF system are considered. Displacement and acceleration response spectra for a shear beam structure subject to the accelerograms of the N00W component of El Centro 1940 and the N90W component of Mexico City 1985 earthquakes and their magnified forms are evaluated. A series of parametric studies is carried out and advantages and disadvantages of various base isolation systems are identified. Comparisons of the results with the response spectra of a fixed‐base structure show that the base isolation systems are, in general, highly effective in reducing the peak acceleration transmitted to the superstructure. Thus, the deflections and stresses generated in a base‐isolated structure are significantly lower than those of a fixed‐base one. Furthermore, the results of the study also show that the friction‐type base isolators are less sensitive to severe variations in frequency content and amplitude of the ground acceleration.
Correlation studies using the equivalent base horizontal acceleration method
Authors: Uang Chia‐Ming , Bertero Vitelmo V. , Clough Ray W.
Published: April 2007

The equivalent base horizontal acceleration concept was developed for calculating the response of test structures to shaking table excitations, to account for pitching interaction effects of the table. Using the procedure, analysis‐experiment comparisons were made of the shaking table tests of a 0–3‐scale model of a six‐storey concentrically K‐braced steel structure. The correlation of the analytical and experimental results was excellent in both the elastic and inelastic ranges of structural response.
Response of base‐isolated buildings to random excitations described by the Clough‐Penzien spectral model
Authors: Lin B. C. , Tadjbakhsh I. G. , Papageorgiou A. S. , Ahmadi G.
Published: April 2007

The stationary response of base‐isolated buildings subjected to earthquake excitation is studied. The frequency content of earthquake input is described by the Clough‐Penzien spectral model. The response parameters of interest are (1) the root‐mean‐square (RMS) displacement σx of the basement relative to the foundation (i.e. shear deformation of the isolation system) and (2) the ratio (σa/σa0) of the RMS value of the absolute acceleration at the roof of the isolated structure over the corresponding value when the isolation system is locked. The variation of these response parameters with the effective frequency f0 of the base‐isolated structure is investigated. As input, earthquakes with moment magnitudes M = 7‐3 and M = 6‐0 are considered. The acceleration spectra corresponding to these two earthquake sizes have pronouncedly different frequency content over the frequency range 0–1‐1–0 Hz which is of primary importance for base‐isolated structures. An important conclusion that comes from these analyses is that confidence in the effectiveness of a base‐isolated system should be based primarily on its capacity to absorb/dissipate energy and less on its influence in shifting the fundamental period of the structure out of the range of dominant earthquake energy.
Simplified analysis method for multistorey base‐isolated structures on viscoelastic halfspace
Authors: Siddiqui Faruq M. A. , Constantinou M. C.
Published: April 2007

A simplified procedure for the analysis of single‐storey base‐isolated structures on a viscoelastic halfspace is extended to multistorey structures. Results of displacements and base shear obtained by this procedure compare favourably to exact results obtained by a computer program that has been developed.
Seismic amplification—Mexico City
Authors: Abbiss C. P.
Published: April 2007

The large amplification experienced at Mexico City during the earthquake of September 1985 is shown to be due to a standing shear wave set up in the clay layer. The frequency and amplitude of this wave were controlled by the properties of the clay which led directly to such high accelerations. The response curve due to the clay layer is calculated from field and laboratory measurements of the properties of the clay. There is good agreement with that obtained from field observations of ground motion.
Steady state rocking response of rigid blocks part 1: Analysis
Authors: Tso W. K. , Wong C. M.
Published: April 2007

The result of a theoretical study on the rocking response of rigid blocks subjected to sinusoidal base motion is presented. The study indicates that, for a given excitation amplitude and frequency, a rigid block can respond in several different ways. Based on analysis, the regions of different classes of steady state symmetric response solutions are mapped on the excitation amplitude‐frequency parameter space. The steady state response solutions (both harmonic and subharmonic) are classified into two classes, out‐of‐phase and in‐phase with respect to the excitation. Only out‐of‐phase solutions are found to be stable. A parametric study shows that steady rocking response amplitude is highly sensitive to the size of the block and the excitation frequency in the low frequency range. It is relatively insensitive to the excitation amplitude and the system's coefficient of restitution of impact. For two blocks of the same aspect ratio and coefficient of restitution subjected to the same excitation, the larger block always responds in smaller amplitude than the smaller block. Computer simulation is carried out to study the stability of the symmetric steady state response solutions obtained from analysis. It is found that as the excitation frequency is decreased beyond the boundary of stable symmetric response, the response becomes unsymmetric where the mean amplitude of oscillation is non‐zero. Further decrease in excitation frequency beyond the stable unsymmetric response boundary causes instability in the form of overturning.
Steady state rocking response of rigid blocks part 2: Experiment
Authors: Wong C. M. , Tso W. K.
Published: April 2007

The results of an experimental investigation on the rocking response of rigid blocks subjected to sinusoidal base motion is presented. It is shown that two common types of steady state response are harmonic and 1/3 subharmonic response. The measured steady state response amplitudes correlate well with theoretical predictions for both harmonic and 1/3 subharmonic responses. Within each type of steady state response, theoretical studies show that the system may respond in either a symmetric or an unsymmetric mode. A symmetric mode denotes that the block oscillates about a mean zero position while an unsymmetric mode implies the mean position of oscillation is at an inclined position. One form of unsymmetric response was observed in the experiment. In addition, almost periodic responses were also observed in the experiment, although their existence has not been reported in theoretical studies.
An algorithm for the optimum design of braced and unbraced steel frames under earthquake loading
Authors: Gülay Gülten , Boduroǧlu Hasan
Published: April 2007

A solution technique based on the sequential linear programming (SLP) method is presented for the optimum design of braced and unbraced steel frames in seismic regions. First, the optimum rigidity distribution of the frames under static loading is computed, then the optimization procedure is repeated under the combined loading, setting lower bounds on the optimum static cross‐sectional areas and increasing allowable stresses.

The stiffness, stress, displacement and side constraints are included in the optimization problem. As a result, a highly non‐linear mathematical programming problem is produced. A non‐linear programming algorithm is offered for the solution which is based on the successive linearization of non‐linear expressions and employs the simplex routine in an iterative manner.

Design variables are chosen to be the free nodal displacements and the cross‐sectional areas of the members, while the objective function is taken to be the minimization of the total volume of the structure.

As numerical applications, optimum weights of several frames (unbraced, concentrically and eccentrically braced) under static and combined loading cases are computed and the results are compared with those available in the literature.
Ritz vectors and generation criteria for mode superposition analysis
Authors: Joo Kuan‐Jung , Wilson Edward L. , Leger Pierre
Published: April 2007

A generation procedure of Ritz vectors to control the inclusion of static effect and the number of vectors in mode superposition dynamic analysis is presented. The original algorithm of the Ritz vectors15 is modified to improve stability in the generation procedure and to include the use of static residual. To reject unimportant Ritz vectors, cut‐off criteria, which are based on the participation of mass distribution and spatial load distribution, are proposed. Numerical examples are presented to illustrate the effectiveness of the derived Ritz vectors over the eigenvectors and the performance of the cutoff criteria in the mode superposition dynamic analysis.
Correlation of cylindrical tank wall buckling with an earthquake motion recorded at a small distance from the tank
Authors: Manos George C. , Shibata Heki , Shigeta Tatsuya
Published: April 2007

The bulging observed on the wall of a ground supported cylindrical storage tank, located at the Chiba Experimental Station of the University of Tokyo, is investigated. This damage is correlated with a ground motion recording obtained very near the tank base during a moderately strong earthquake that occurred on September 25, 1980 not far from the Chiba Experimental Station. From this correlation the importance of the horizontal excitation in amplitude and direction is clearly established. In addition, good agreement can be seen between the predicted tank wall earthquake performance, derived by an empirical approach proposed by the first author, and the shell deformation observed at the Chiba Experimental Station.