bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Preparation of Poly(acriflavine) Film‐Modified Electrode and Its Electrolcatalytic Properties Towards NADH, Nitrite and Sulfur Oxoanions
Authors: Chen Shen‐Ming , Liu Meei‐Ing , Kumar S. Ashok
Published: March 2007

Electrochemical polymerization of acriflavine (AF) was carried out onto glassy carbon electrodes (GCE) from the aqueous buffer solution containing 1.5×10−3 M AF monomer (pH 3.5) which produced a thin electrochemically active film. This is noted as poly(AF) film modified electrodes (PAF/GCE). This modified electrode was shown a stable reversible redox couple centered at +0.22 V in pH 3.5 buffer solutions. PAF/GCE was found to be more stable in acidic solutions and its formal potential was found to be pH dependent with a slope close to −60 mV/pH. The electrochemical deposition kinetics of poly(AF) onto gold coated quartz crystal was studied by using electrochemical quartz crystal microbalance (EQCM) combined with cyclic voltammetry (CV). PAF/GCE was found be good mediator for electrochemical oxidation of reduced nicotinamide adenine dinucleotide (NADH) in pH 5 buffer solutions. The electrocatalytic oxidation of SO$\rm{ _3^{2 - } }$ and electrocatalytic reduction of NO$\rm{ _2^ - }$, SO$\rm{ _5^{2 - } }$ and S2O$\rm{ _8^{2 - } }$ were carried out at PAF/GCE electrode in acidic aqueous solutions. The electrocatalytic oxidation of NADH was also investigated by using amperometric method.
Electrochemical Catalytic Processes with Hydrogen Peroxide Showing Oxidative and Reductive Properties (Acting as Oxidant or Reductant)
Authors: Pacześniak Tomasz , Błoniarz Paweł , Rydel Katarzyna , Sobkowiak Andrzej
Published: March 2007

It has been found that hydrogen peroxide can act as an oxidant and as a reductant of transition metal complexes in acetonitrile. Therefore, the examples of catalytic currents of oxidants and reductants has been described. In the case of Co(acac)3 both the types of catalytic currents are present in a single cyclic‐voltammetric scan.
Transients in cylindrical shells
Authors: Thambiratnam D. P. , Shah A. H. , Cohen H.
Published: March 2007

The propagation of non‐axially symmetric transients in linear, elastic, isotropic and homogeneous cylindrical shells subjected to impulsive boundary loads is treated in this paper. Expressing the displacement components in the form of a Fourier series in the circumferential co‐ordinate, the displacement equations of motion are written for each harmonic.

The analysis is based on the concept of a wave as a carrier of discontinuities in the field variable and its derivatives. These discontinuities are determined from a set of recurrence relations which are in turn generated by the use of time‐harmonic asymptotic series solutions to the equations of motion. The method is illustrated by presenting detailed numerical results pertaining to the influence of earthquake or blast‐induced ground excitation on cylindrical tanks.
Seismic dynamic response by approximate methods
Authors: Bieber Ray E. , Hovland H. John
Published: March 2007

Current seismic safety evaluation for earth dams relies on approximate methods of analysis for prediction of non‐linear, transient, dynamic response. One of these approximate methods uses a Strain Reduction Factor (SRF), and has been widely applied in a variety of one‐dimensional and two‐dimensional soil structural analyses. A second method considered, Equivalent Temporal Damping (ETD), has been previously applied to several seismic dynamic analyses of earth dams. The relative accuracy of the two methods is assessed by comparing them with incremental plasticity, nearly exact numerical solutions. For a simple shear element subjected to deterministic and non‐stationary random input accelerations, a serious overprediction of the maximum peak shear response occurs by the SRF method, whereas the ETD results agree very closely with the incremental plasticity solutions. The SRF and ETD methods are also applied to seismic dynamic response analysis of a Vertical Soil Column system, and the same trends as established in the previous case are observed. It is concluded that, in lieu of combined incremental plasticity and finite difference or finite element numerical solutions, the ETD approach is the more accurate of the methods tested for seismic dynamic response analysis of earth dams.
Bridge dynamic loading due to road surface irregularities and braking of vehicle
Authors: Gupta R. K. , Traill‐Nash R. W.
Published: March 2007

Single span highway bridges of composite construction are idealized as beams as well as orthotropic plates. A standard HS–20–44 highway vehicle is represented by a planar, two‐axle, sprung mass system with frictional device. The response equations are derived in terms of the natural modal co‐ordinates of the bridge and of displacement co‐ordinates of the vehicle. The road surface irregularities, generally found at the junctions of the approach road and bridge ends, are idealized as a 45° ramp. The maximum impact factors for bending moment and deflection are obtained due to the ramp and in combination with the braking of vehicle for symmetric as well as essentric loading of the vehicle.
The estimation of earthquake‐generated additional tension in a suspension bridge cable
Authors: Irvine H. M.
Published: March 2007

A simple formula, equation (15), is derived for the peak additional cable tension that can be expected in a suspension bridge undergoing earthquake excitation. The method involves application of the response spectrum technique and rests on several plausible assumptions. The formula gives a reasonable upper bound, suitable for preliminary design estimates, irrespective of whether the ground motions at each end are in‐phase or, as is probable with a long span bridge, whether they are out‐of‐phase.
Base isolation for torsion reduction in asymmetric structures under earthquake loading
Authors: Lee David M.
Published: March 2007

This paper examines the effectiveness of a bilinear hysteretic base isolation system in lowering the shear forces and torques generated in a structure by two‐way, translatory ground motions. The study is restricted to single‐storey, three‐dimensional structures having asymmetries in both horizontal directions and being excited by the El Centro (May 1940) earthquake motions.

It is shown that with base isolation the structural torques are drastically reduced, even if the structural eccentricity is large. This reduction in structural torque is greatest when the isolation system's centre of stiffness coincides with the structure's centre of mass. The highly dissipative action of the isolation system provides strong modal decoupling which prevents the translational motions from resonantly driving the torsional motions. The maximum base displacements, due to both translation and rotation combined are less than 11 cm, which is well within the limits of currently available isolation system components.

The dynamic action of the base isolation system is outlined and currently available isolation system components described.
Estimating inelastic response spectra from elastic spectra
Authors: Iwan W. D.
Published: March 2007

Inelastic displacement response spectra are determined for a broad class of single‐degree‐of‐freedom hysteretic structures. Based on these spectra, effective linear period and damping parameters are defined as a function of ductility. A simple empirical formula is derived which may be used to estimate the mid‐period range inelastic response spectrum of a general hysteretic structure given the linear response spectrum of the excitation. The estimates obtained from this formula are compared with those obtained by the Newmark‐Hall method, the substitute–structure method and the ATC–3 tentative procedure. It is found that the empirical formula not only gives good estimates of the average behaviour of the inelastic spectrum, but also reproduces some of the details of the spectrum.
Soil—foundation interaction and differential ground motions
Authors: Bycroft G. N.
Published: March 2007

Differential ground motions due to horizontally propagating surface waves are of importance in determining the stresses and displacements developed in extended structures such as large mat foundations for nuclear power stations, dams, bridges and pipe‐lines. A general method is developed for determining the motion of a large rigid mat foundation subjected to travelling surface waves and observations made on the relative displacements of individual foundations and their importance in bridge failure.
Vibrations of the elastic half‐space due to vertical surface loads
Authors: Holzlöhner U.
Published: March 2007

The displacements of the surface of the homogeneous elastic half‐space subjected to a vertical concentrated load acting at the surface are calculated. The solution is shown to approach Lamb's simple formula for the far‐field. The solution for the concentrated load can be used to calculate displacements due to distributed loads with high accuracy and economically. The results are applied to define the regions ‘near‐field’ and ‘far‐field’. Some near‐field phenomena are described.
Influence of geometry and of the constitutive law of the supporting columns on the seismic response of a hyperbolic cooling tower
Authors: Wolf J. P. , Skrikerud P. E.
Published: March 2007

The supporting columns and their foundation influence the cooling tower's seismic response decisively. At the same time, they represent the most vulnerable part of the structure. To determine the optimum seismic design, the influence of the geometry of the columns is investigated parametrically. The dominant parameter, the in‐plane angle of inclination, should be selected to be as large as possible. For a specific geometric configuration, the response for increasing seismic excitation is studied. The constitutive laws of the concrete and of the reinforcement steel in the columns as well as slipping and lift‐off of the foundations are incorporated into a non‐linear analysis. The largest reduction in response results from the behaviour of the columns in tension. The tower can thus withstand much larger seismic excitations than those indicated in a linear analysis. Slipping and lift‐off, which develop for extreme earthquakes only, play a less important role, even when occurring in the entire foundation.
Response of a circular cylindrical shell to disturbances in a half‐space
Authors: El‐Akily Nabil , Datta S. K.
Published: March 2007

The response of a circular cylindrical shell to disturbances in an elastic half‐space is the subject of this paper. Two methods of solution are presented. The first is a method of matched asymptotic expansions, and the second is a method of successive reflections.
Rocking response of rigid blocks to earthquakes
Authors: Yim Chik‐Sing , Chopra Anil K. , Penzien Joseph
Published: March 2007

This investigation deals with the rocking response of rigid blocks subjected to earthquake ground motion. A numerical procedure and computer program are developed to solve the non‐linear equations of motion governing the rocking motion of rigid blocks on a rigid base subjected to horizontal and vertical ground motion.

The response results presented show that the response of the block is very sensitive to small changes in its size and slenderness ratio and to the details of ground motion. Systematic trends are not apparent: The stability of a block subjected to a particular ground motion does not necessarily increase monotonically with increasing size or decreasing slenderness ratio. Overturning of a block by a ground motion of particular intensity does not imply that the block will necessarily overturn under the action of more intense ground motion.

In contrast, systematic trends are observed when the problem is studied from a probabilistic point of view with the ground motion modelled as a random process. The probability of a block exceeding any response level, as well as the probability that a block overturns, increases with increase in ground motion intensity, increase in slenderness ratio of the block and decrease in its size.

It is concluded that probabilistic estimates of the intensity of ground shaking may be obtained from its observed effects on monuments, minarets, tombstones and other similar objects provided suitable data in sufficient quantity is available, and the estimates are based on probabilistic analyses of the rocking response of rigid blocks, considering their non‐linear dynamic behaviour.
Overturning effects in stiffened building frames
Authors: Huckelbridge Arthur A. , Ferencz Robert M.
Published: March 2007

In this paper seismically induced overturning effects in stiffened building frames are studied by examining the response of two structures: a 20‐storey ‘core wall’ reinforced concrete frame and a 10‐storey steel braced frame. The excitations utilized in the study are the 1971 Pacoima Dam S16E Record and the 1940 El Centro N‐S Record magnified by a factor of two. Non‐linear effects of the following types are considered: plastic hinging of beams and columns, yielding and/or buckling of bracing members and transient uplift of portions of the structures from the foundation. In particular, comparisions are made between response with unlimited base overturning capacity assumed and response with dead‐weight overturning resistance only. Providing dead‐weight overturning resistance only is shown to significantly reduce seismic load levels, with relatively little or no loss in drift control. Ductility demand in these stiffened frames is shown to be limited, when transient uplift is allowed, to the link beams connecting stiffened and unstiffened portions of the structures.
Modal methods in the dynamics of systems with non‐classical damping
Authors: Traill‐Nash R. W.
Published: March 2007

When damping in a system is both significantly high and its distribution is non‐classical the solution of dynamical problems by conventional modal analysis is complicated by the presence of coupling between the normal co‐ordinates. Further, the convergence of a solution may be erratic with successive modal additions, leading to the need to include a larger number of modes than would otherwise be expected. In this paper methods of modal analysis in structural dynamics are discussed and their derivations briefly given. These include the conventional mode displacement method and the force summation method, employing normal modes, and the analogous procedures with damped modes. In the latter, dynamic response equations are not coupled. Dynamic loading solutions by the four approaches, each taking account of the non‐classical damping distribution, are demonstrated with a simple model representing a structure on a compliant foundation. The results strongly suggest that the use of damped modes with force summation could be the most effective procedure when damping is non‐classical.
Effect of earth media on the seismic motion of embedded rigid structures
Authors: Fedock Joseph J. , Schreyer Howard L.
Published: March 2007

A finite element analysis is performed to determine the influence of the choice of a constitutive model for the earth medium upon the response to seismic waves of an embedded rigid structure. The seismic forcing function is characterized by Rayleigh waves with amplitude parameters adjusted to provide identical free‐field motion at a surface reference point for one particular sand represented with elastic, plastic and viscoelastic models. Within the limitations of the analysis, the result is that the steady‐state rigid body motions of the embedded structure are essentially identical for these constitutive relations and, consequently, it is appropriate to use an elastic representation for the earth medium.
Surface waves in a half‐space of submerged sand
Authors: Vardoulakis I.
Published: March 2007

The present analysis deals with harmonic Rayleigh‐type and transverse surface waves in a half‐space of incompressible material with constant density and with shear modulus linearly increasing with depth. This model is proposed for describing the response of a half‐space of submerged, dense sand to small strain vibrations of many cycles. It is shown that a discrete spectrum of polynomial solutions is always possible which makes the eigenvalue problem more tractable.
A response spectrum method for random vibration analysis of mdf systems
Authors: Kiureghian Armen Der
Published: March 2007

A response spectrum method for stationary random vibration analysis of linear, multi‐degree‐of‐freedom systems is developed. The method is based on the assumption that the input excitation is a wide‐band, stationary Gaussian process and the response is stationary. However, it can also be used as a good approximation for the response to a transient stationary Gaussian input with a duration several times longer than the fundamental period of the system. Various response quantities, including the mean‐squares of the response and its time derivative, the response mean frequency, and the cumulative distribution and the mean and variance of the peak response are obtained in terms of the ordinates of the mean response spectrum of the input excitation and the modal properties of the system. The formulation includes the cross‐correlation between modal responses, which is shown to be significant for modes with closely spaced natural frequencies.

The proposed procedure is demonstrated for an example structure that is subjected to an ensemble of earthquake‐induced base excitations. Computed results based on the response spectrum method are in close agreement with simulation results obtained from time‐history dynamic analysis. The significance of closely spaced modes and the error associated with a conventional method that neglects the modal correlations are also demonstrated.
Response spectrum techniques for three‐component earthquake design
Authors: Anagnostopoulos Stavros A.
Published: March 2007

An evaluation is made of response spectrum techniques as applied to seismic analysis and design of steel template offshore platforms. Such structures are designed as braced space frames for several loading conditions, including the simultaneous action of three earthquake components. Base shears as well as gross forces and combined stresses in members of three different platforms are computed for 30 real, three‐component earthquakes and response spectrum predictions, obtained by several modal‐spatial combination methods, are compared to time history solutions. Results are presented in the form of error statistics.

The three approximations examined are: (a) combination of modes for one component input, (b) combination of the three partial responses to obtain estimates of total response and (c) combination of gross forces to derive maximum design stresses at a section. Attention is focused on corner piles because these are among the most heavily penalized members by three‐component excitations.

It is shown that commonly used spatial combination rules may underestimate gross forces in design controlling corner members by 15–30 per cent on the average. This is attributed to correlations between motion components that create additive effects along certain directions. Typical estimates of combined stresses, however, are found to be slightly conservative.
Response of a circular cylindrical shell to disturbances in a half‐space—numerical results
Authors: El‐Akily Nabil , Datta S. K.
Published: March 2007

In this paper we present numerical results representing the response of an elastic cylindrical shell to disturbances in an elastic half‐space. These numerical results show the radial displacement at the middle surface of the shell and the hoop stress in the shell. The incident disturbance is in the form of a plane dilatational wave or a Rayleigh wave.
Generation of lateral and rotational floor response spectra by an alternative approach
Authors: Ishac Magdi F. , Heidebrecht Arthur C.
Published: March 2007

A procedure is described to compute the lateral and rotational floor response spectra of an asymmetric reactor building structure without a time history analysis. The spectral values obtained by filtering the prescribed ground motion first through the structure and the resulting lateral‐rotational motions through simple oscillators are equal to the maximum lateral‐rotational responses of the structure developed when the order of filtration is reversed. Based on the preceding concept a deterministic method is presented to construct the lateral‐rotational floor response spectra utilizing the response spectrum technique.
Hydrodynamic and foundation interaction effects in frequency response functions for concrete gravity dams
Authors: Chopra Anil K. , Gupta Sunil
Published: March 2007

The linear response of idealized dam cross‐sections to harmonic horizontal or vertical ground motion is presented for a range of the important system parameters characterizing the properties of the dam, foundation rock and impounded water. Based on these frequency response functions, the separate effects of interaction between the dam and water and interaction between the dam and foundation, and the combined effects of the two sources of interaction, on dynamic response of dams are investigated.
Soil‐pile interaction in vertical vibration induced through a frictional interface
Authors: Akiyoshi T.
Published: March 2007

The interaction between a soil layer and an end bearing pile in vertical vibration induced through the frictional interface is theoretically investigated. The pile is assumed to be vertical and elastic, whereas the soil is considered as a linear visco‐elastic layer with hysteretic damping. Slip between the pile and the soil is allowed to occur along the frictional interface, in which the hysteretic frictional stress is linearized to permit modal decomposition. Approximate solutions of the pile and the soil for steady‐harmonic loads are obtained in closed form by composing the wave modes of the layer. The displacement amplitudes of the pile and the soil, the critical slip force, the stiffness of the pile head, and the modal stiffness contribution of the soil to the pile are evaluated numerically with respect to the ratio of applied force level to the slip stress level and the slenderness ratio, at various frequencies.
An engineering prediction model of acceleration response spectra and its application to seismic hazard mapping
Authors: Katayama Tsuneo
Published: March 2007

A regression analysis was made on 277 acceleration response spectra computed from Japanese accelerograms by subdividing the data into discrete categories. Five magnitude and distance categories, and four ground condition categories were used. The maximum absolute acceleration amplitude is predicted as a product of three factors, each representing a weighting factor for magnitude, distance and ground condition category at each of the 18 response spectrum periods from 0·1 s to 4 s at a damping value of 5 per cent of critical. A method was then developed to evaluate seismic hazard in terms of acceleration response spectrum by using the prediction model and the seismicity data, and it was applied to obtain seismic macro‐zoning maps of Japan which are dependent on the natural period of a structure. The results of the analysis indicated that a single seismic zoning map may not be sufficient to cover a variety of structures with a wide range of periods because the expected spectral shape differs according to the seismicity of the area.
An imposed force summation method for non‐linear dynamic analysis
Authors: Dungar R.
Published: March 2007

A method of obtaining the response of a non‐linear system is proposed, which involves imposing the solution upon the equations of motion for a linear system and solving using selected modes of vibration. Contribution from the remaining modes of the system is included in terms of their quasi‐static response. The method is developed and illustrated with reference to a system with material non‐linearity and special reference is given to the dynamic analysis of embankment dams.
A note on the perturbation analysis of the mode shapes of torsionally coupled buildings
Authors: Tsicnias T. G. , Hutchinson G. L.
Published: March 2007

The application of perturbation analysis in torsionally coupled buildings makes it possible to obtain an approximation of the dynamic properties of the buildings in question by combining appropriately the dynamic properties of the corresponding torsionally uncoupled buildings. This note aims to clarify the results obtained from a second‐order perturbation analysis of the mode shapes of torsionally coupled buildings. Numerical examples of building models are given to illustrate the theoretical points.
Seismic safety of reinforced concrete members and structures
Authors: Banon Hooshang , Veneziano Daniele
Published: March 2007

Based on cyclic load tests of large‐scale reinforced concrete elements and assemblages, a probabilistic model of member failure is developed. The model gives the probability of survival at time t as a functional of damage ratio and dissipated energy up to t. After extension to multivariate survival of several members with correlated resistance, the model is used to calculate the safety of reinforced concrete frames subjected to given input motions. Results are in terms of the probability of local failure and of no failure anywhere in the system.
Apparent propagation velocity of body waves
Authors: O'Rourke Michael J. , Bloom Mary C. , Dobry Ricardo
Published: March 2007

The apparent horizontal propagation velocity, that is the propagation velocity of seismic waves with respect to the ground surface, is discussed in this paper. This parameter is needed to determine the effects of earthquakes on long structures such as bridges and buried pipelines as well as the torsional rotation of foundations of multi‐storey buildings. A time window intensity tensor introduced by Penzien and Kubo is used herein to determine the predominant directions of ground motion during an earthquake. Considering the reflection of waves at a free surface, an approximate relationship between the predominant direction and the angle of incidence of body waves with respect to the ground surface is presented. Knowing the material properties of the top layer and the angle of incidence, the desired propagation velocity with respect to the ground surface is readily calculated.

The median value of the apparent propagation velocity of shear waves for near field sites which recorded the 1971 San Fernando earthquake was determined to be about 2‐1 km/s using the above method. A similar value for the 1979 Imperial Valley earthquake is 3·7 km/s. These values are consistent with the range of values for the apparent propagation velocity determined by other researchers.
Hydrodynamic effects in the dynamic response of concrete gravity dams
Authors: Hall John F. , Chopra Anil K.
Published: March 2007

Hydrodynamic effects in the acceleration response of concrete gravity dams to harmonic ground motion are investigated. The effects include the presence of water, compressibility of water, interaction between the fluid and underlying foundation medium, shape of the fluid domain, and the extent of excitation applied to an infinite fluid domain under vertical ground motion.
Stochastic response of multistorey yielding frames
Authors: Baber Thomas T. , Wen Yi‐Kwei
Published: March 2007

A model for the random vibration of hysteretic and degrading plane frames to Gaussian shot noise or filtered shot noise is presented. The model, which combines the discrete hinge concept previously used in deterministic frame analysis with Bouc's smooth system hysteresis, results in a non‐linear set of differential equations which can be linearized in closed form without recourse to the Krylov‐Bogoliubov assumptions. Solution is iterative in the stationary case and by numerical integration with stepwise updates in the non‐stationary case. Numerical studies are presented of strong girder and strong column two storey, one bay frames. These studies indicate that the model can locate the sites of yielding and provide reasonable values of structural response as compared with simulation data. Moreover, the model can provide a joint by joint breakdown of the structure energy dissipation rate.
Hydrodynamic effects in dynamic response of simple arch dams
Authors: Porter Craig S. , Chopra Anil K.
Published: March 2007

The dynamic responses of simple arch dams, with different radius to height ratios are analysed for three conditions: the dam alone without water, and the dam with full reservoir, considering water to be compressible in one case and neglecting water compressibility in the other case. The complex frequency response functions for accelerations at the dam crest due to the three components of ground motion—upstream‐downstream component, cross‐stream component and vertical component–are presented. Based on these results, the effects of dam‐water interaction, of water compressibility, and of bank motions on dam response are investigated.
Investigation of the elastic characteristics of a three‐storey steel structure using system identification
Authors: Kaya Izak , McNiven Hugh D.
Published: March 2007

In this report, three different models in increasing order of complexity have been used to identify the seismic behaviour of a three‐storey steel structure subjected to arbitrary forcing functions, all of which excite responses within the elastic range. All of the models are constructed using system identification.

In the first model, five parameters have been used to identify the frame. Treating the system as a shear building, we assign one stiffness coefficient to each floor and introduce Rayleigh‐type damping with two additional parameters. The mass, assumed to be concentrated at a floor level, is kept constant throughout the study. The parameters are established using a modified Gauss‐Newton algorithm. The match between measured and predicted quantities is satisfactory when these quantities are restricted to floor accelerations or displacements.

To remove the constraint imposed by assuming that the frame deforms as a shear building, a second model with eight parameters is introduced, allowing rotations of the joints as independent degrees of freedom. Six of the eight parameters are related to the stiffness characteristics of the structural members while the remaining two are related to damping as before.

In constructing the eight‐parameter model, we learned that it is the effective lengths of the members that change during optimization. We also found that the independent response quantities, floor accelerations and joint rotations, must be used in the cost function for the optimization algorithm to converge.

The match between measured and predicted quantities for the eight‐parameter model is excellent. The set of parameters derived from the minimum squared error gives a model that shows very good correlation using information on the full duration of the pulse or only a portion of it. Also the same correlation exists between the coefficients obtained from different excitations.

In an effort to explain the values of the parameters associated with the girders, an additional degree of freedom, namely, the pitching motion of the shaking table, is introduced as an additional degree of freedom. The paper presents, therefore, a five‐, an eight‐ and, finally, a nine‐parameter model.
Three‐dimensional dynamic analysis for multi‐component earthquake spectra
Authors: Wilson Edward L. , Button Martin R.
Published: March 2007

At the present time, there is a need for a rational approach for the analysis and design of three‐dimensional structures subjected to multi‐component earthquake motions. In this paper, a general design criterion for multi‐component earthquake input is proposed. A new method for three‐dimensional dynamic analysis is presented which estimates maximum displacements, forces or stresses for specified points within a structure. For each maximum value calculated, the corresponding critical angle of earthquake input is evaluated. The method is readily incorporated into existing computer programs for earthquake analysis, allowing one computer run to produce mean maximum response values for all possible angles of earthquake input. Combined axial and bending stresses are calculated at the modal level. It is shown that combining modal stresses yields lower estimates than if stresses are evaluated from maximum axial forces and moments. In addition, the method can be used without modifications to perform design checks for arbitrary blast or seawave spectra.
Frequency‐domain redigitization method for seismic time histories
Authors: Liou D. D.
Published: March 2007

This note presents a numerical method for redigitizing a given time history at a smaller time increment than that used to define the time history without changing its original frequency content. Both the theoretical basis and the numerical procedure of this method are presented. A numerical example is also given in order to demonstrate the advantage of this method over the linear interpolation method commonly used in the industry.
A new approach to the integration of accelerometer data
Authors: Trujillo D. M. , Carter A. L.
Published: March 2007

A direct approach to the integration of accelerometer data is presented which depends only on the fact that the final velocity and possibly, the final displacement are known. Using a dynamic programming formulation, the accelerometer record is corrected to account for these cases. The formulation is presented for the general case where velocity, displacement, as well as accelerometer data, are available. A numerical example is included.
The ρ‐family of algorithms for time‐step integration with improved numerical dissipation
Authors: Bazzi G. , Anderheggen E.
Published: March 2007

The dynamic analysis of complex non‐linear structural systems by the finite element approach requires the use of time‐step algorithms for solving the equations of motion in the time domain. Both an implicit and an explicit version of such a time‐step algorithm, called the ρ‐method, the parameter ρ being used for controlling numerical damping in the higher modes, are presented in this paper. For the implicit family of algorithms unconditional stability, consistency, convergence, accuracy and overshoot properties are first discussed and proved. On the basis of the algorithmic damping ratio (dissipation) and period elongation (dispersion) the ρ‐method is then compared with the well‐known implicit algorithms of Hilber, Newmark, Wilson, Park and Houbolt. An explicit version of the algorithm is also derived and briefly discussed. This shows numerical properties similar to the central difference method. Both versions of the algorithm have been implemented in a general purpose computer program which has been often used for both numerical tests and practical applications.
Seismic risk analysis for Northern Iraq
Authors: Puttonen Jari , Varpasuo Pentti
Published: March 2007

In this study the seismic risks of northern Iraq have been evaluated by a probabilistic method. The data contain about 500 earthquakes which occurred between 1840 and 1978. The epicentral locations and magnitudes of the included earthquakes have been presented.

A linear relationship between magnitude and frequency has been assumed. The attenuation of intensities has been presented as a function of magnitude and epicentral distance.

The seismic risk has been calculated for 225 points of the analysed area. The equiseismal maps related to a certain risk level have been plotted by using these point values of intensities, and assuming a linear variation between the points. The significance of the standard deviation of the attenuation law and the strict lower bound intensity has been investigated by sensitivity analyses.

The intensity contours related to the annual return period of 50, 100 and 200 years have been presented, and also the intensity contours with an occurrence probability of 10 per cent during 50, 100 and 200 years have been drawn.
Dynamic behaviour of rigid foundations of arbitrary shape on a halfspace
Authors: Rüucker Werner
Published: March 2007

An approximate method for computation of the compliance functions of rigid plates resting on an elastic or visco‐elastic halfspace excited by forces and moments in all degrees of freedon is presented. The method is based on a Green's function approach. These functions are given for all degrees of freedom in form of well‐behaved integrals. The numerical procedure is described and is used to evaluate the vertical, horizontal, rocking and torsion compliance functions of rectangular plates with side ratios 1 ≤ b/a ≤ 10 and non‐dimensional frequency 0≤a0≤10. It is shown how this method can be extended to problems concerning a linear visco‐elastic halfspace and a halfspace with variable stiffness.
Infinite elements for elastodynamics
Authors: Medina Franciso , Penzien Joseph
Published: March 2007

An axisymmetric infinite element and a three‐dimensional infinite element are developed to solve three‐dimensional elastic wave propagation problems in unbounded media. The elements are capable of transmitting Rayleigh, shear and compressional waves in the frequency domain. A scheme to integrate numerically the characteristic matrices of the elements is formulated based upon Gauss—Laguerre quadrature. Finally, the axisymmetric infinite element is used to find the compliance functions of a rigid circular plate subjected to harmonic loading on a semi‐infinite medium. By using infinite elements, the size of the near field may be kept small. Consequently, the system is characterized by relatively few degrees of freedom, thus providing the analyst with an inexpensive solution.
A re‐evaluation of equivalent linear models for simple yielding systems
Authors: Hadjian A. H.
Published: March 2007

Commonly used equivalent linear models for simple yielding systems subjected to harmonic and earthquake excitations are re‐evaluated. It is shown that with respect to damping, these models contain the same basic information. Reported differences in the literature are simply due to scaling: since the product of the equivalent stiffness and equivalent damping is a constant, smaller damping values would be obtained by the use of the small amplitude equivalent stiffnesses. It is argued that for harmonic excitation, the secant stiffness is an appropriate representation of equivalent stiffness, leading to large equivalent damping values that increase with ductility. For earthquake excitation the Iwan proposal is shown to be the preferred model leading to larger damping values than previously reported. A comparison of the models for harmonic and earthquake excitations shows that, in general, and at comparable ductilities, damping values due to harmonic excitation are about five times those due to earthquake excitation, and the period changes due to harmonic excitation are about twice those due to earthquake excitation.
Bounds on earthquake response of elastic columns
Authors: Ahmadi Goodarz , Mostaghel Naser
Published: March 2007

The dynamics of an elastic column subjected to vertical as well as horizontal ground acceleration during an earthquake strong motion is considered. The Liapunov method of stability analysis is employed and several bounds on the maximum lateral displacement and bending stress are obtained and discussed.
Properties and extensions of a single‐step algorithm for dynamic problems
Authors: Thomas R. M.
Published: March 2007

Recently, a new class of single‐step methods for solving linear systems of second order ordinary differential equations has been introduced by Zienkiewicz et al.1 We derive the stability, phase and damping properties of these methods and suggest some possible improvements with the aim of improving accuracy.
Effects of microbiotic crusts under cropland in temperate environments on soil erodibility during concentrated flow
Authors: Knapen A. , Poesen J. , Galindo‐Morales P. , Baets S. De , Pals A.
Published: March 2007

Several studies illustrate the wind and water erosion‐reducing potential of semi‐permanent microbiotic soil crusts in arid and semi‐arid desert environments. In contrast, little is hitherto known on these biological crusts on cropland soils in temperate environments where they are annually destroyed by tillage and quickly regenerate thereafter. This study attempts to fill the research gap through (a) a field survey assessing the occurrence of biological soil crusts on loess‐derived soils in central Belgium in space and time and (b) laboratory flume (2 m long) experiments simulating concentrated runoff on undisturbed topsoil samples (0.4 × 0.1 m2) quantifying the microbiotic crust effect on soil erosion rates. Three stages of microbiotic crust development on cropland soils are distinguished: (1) development of a non‐biological surface seal by raindrop impact, (2) colonization of the soil by algae and gradual development of a continuous algal mat and (3) establishment of a well‐developed microbiotic crust with moss plants as the dominant life‐form. As the silt loam soils in the study area seal quickly after tillage, microbiotic soil crusts are more or less present during a large part of the year under maize, sugar beet and wheat, representing the main cropland area. On average, the early‐successional algae‐dominated crusts of stage 2 reduce soil detachment rates by 37%, whereas the well‐developed moss mat of stage 3 causes an average reduction of 79%. Relative soil detachment rates of soil surfaces with microbiotic crusts compared with bare sealed soil surfaces are shown to decrease exponentially with increasing microbiotic cover (b = 0·024 for moss‐dominated and b = 0·006 for algae‐dominated crusts). In addition to ground surface cover by vegetation and crop residues, microbiotic crust occurrence can therefore not be neglected when modelling small‐scale spatial and temporal variations in soil loss by concentrated flow erosion on cropland soils in temperate environments. Copyright © 2007 John Wiley & Sons, Ltd.
High‐resolution interpretative geomorphological mapping of river valley environments using airborne LiDAR data
Authors: Jones Anna F. , Brewer Paul A. , Johnstone Eric , Macklin Mark G.
Published: March 2007

The availability of airborne LiDAR data provides a new opportunity to overcome some of the problems associated with traditional, field‐based, geomorphological mapping such as restrictions on access and constraints of time or cost. The combination of airborne LiDAR data and GIS technology facilitates the rapid production of geomorphological maps of floodplain environments; however, unfiltered LiDAR data, which include vegetation and buildings, are currently more suitable for geomorphological mapping than data that have been filtered to remove these features. Classification of LiDAR data according to elevation in a GIS enables the user to identify and delineate geomorphological features in a manner similar to field mapping, but it is necessary to use a range of classification intervals in order to map the various types of feature that occur within a single reach. Comparison of a LiDAR‐derived geomorphological map with an independently produced field geomorphological map showed a high degree of similarity between the results of the two methods, although ground‐truthing is essential in cases where a high degree of accuracy is required. Ground‐truthing of a LiDAR‐derived geomorphological map showed that around 80% of features mapped using both methods were identified from the LiDAR data, suggesting that the method is suitable for applications such as production of base maps for use in field mapping and selection of sites for detailed investigation. Copyright © 2007 John Wiley & Sons, Ltd.
G protein‐coupled receptor 84, a microglia‐associated protein expressed in neuroinflammatory conditions
Authors: Bouchard Caroline , Pagé Julie , Bédard Andréanne , Tremblay Pierrot , Vallières Luc
Published: March 2007

G protein‐coupled receptor 84 (GPR84) is a recently discovered member of the seven transmembrane receptor superfamily whose function and regulation are unknown. Here, we report that in mice suffering from endotoxemia, microglia express GPR84 in a strong and sustained manner. This property is shared by subpopulations of peripheral macrophages and, to a much lesser extent, monocytes. The induction of GPR84 expression by endotoxin is mediated, at least in part, by proinflammatory cytokines, notably tumor necrosis factor (TNF) and interleukin‐1 (IL‐1), because mice lacking either one or both of these molecules have fewer GPR84‐expressing cells in their cerebral cortex than wild‐type mice during the early phase of endotoxemia. Moreover, when injected intracerebrally or added to microglial cultures, recombinant TNF stimulates GPR84 expression through a dexamethasone‐insensitive mechanism. Finally, we show that microglia produce GPR84 not only during endotoxemia, but also during experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. In conclusion, this study reports the identification of a new sensitive marker of microglial activation, which may play an important regulatory role in neuroimmunological processes, acting downstream to the effects of proinflammatory mediators. © 2007 Wiley‐Liss, Inc.
High‐resolution electroencephalography and source localization in neonates
Authors: Roche‐Labarbe Nadège , Aarabi Ardalan , Kongolo Guy , Gondry‐Jouet Catherine , Dümpelmann Matthias , Grebe Reinhard , Wallois Fabrice
Published: March 2007

Although Electroencephalography (EEG) source localization is being widely used in adults, this promising technique has not yet been applied to newborns because of technical difficulties, such as lack of data concerning the newborn skull conductivity, thickness, and homogeneity. Using a new type of EEG headcap molded on each baby's head, we aimed to determine whether this technique could be adapted to neonates, and to evaluate the importance of these technical difficulties. We carried out EEG source reconstruction of the recordings of five neonates using dipole fit algorithm. We used four different head models for each neonate, obtained from individual MRI scans: normal skull thickness and conductivity of 0.0042 S/m; normal thickness and conductivity of 0.33 S/m; increased thickness and conductivity of 0.0042 S/m; and normal thickness and conductivity with a modeled bregma fontanel. Dipole locations were consistent with MRI and clinical data. The mean difference between the dipole locations in the 0.0042 and the 0.33 S/m skull layer models was 11.6 ± 2.5 mm, with an average 29.7% decrease in magnitude for the 0.33 S/m model but no significant changes for the dipoles orientation. Skull layer thickness had a large influence on magnitude, but no significant effect on position and orientation. The mean difference between the dipole locations induced by the modeled fontanel was 2.0 ± 2.1 mm, with an average 2.1% increase in magnitude. Our results show that EEG source localization is feasible in neonates. With further development, the technique may prove useful for neurological evaluation of neonates. Hum Brain Mapp, 2008. © 2007 Wiley‐Liss, Inc.
Model‐based clustering of meta‐analytic functional imaging data
Authors: Neumann Jane , Cramon D. Yves von , Lohmann Gabriele
Published: March 2007

We present a method for the analysis of meta‐analytic functional imaging data. It is based on Activation Likelihood Estimation (ALE) and subsequent model‐based clustering using Gaussian mixture models, expectation‐maximization (EM) for model fitting, and the Bayesian Information Criterion (BIC) for model selection. Our method facilitates the clustering of activation maxima from previously performed imaging experiments in a hierarchical fashion. Regions with a high concentration of activation coordinates are first identified using ALE. Activation coordinates within these regions are then subjected to model‐based clustering for a more detailed cluster analysis. We demonstrate the usefulness of the method in a meta‐analysis of 26 fMRI studies investigating the well‐known Stroop paradigm. Hum Brain Mapp, 2008. © 2007 Wiley‐Liss, Inc.