bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of chemical reaction, heat and mass transfer on non‐linear MHD flow over an accelerating surface with heat source and thermal stratification in the presence of suction or injection
Authors: Anjali Devi S. P. , Kandasamy R. 
Published: July 2003

AbstractAn approximate numerical solution for the steady MHD laminar boundary‐layer flow over an accelerating vertical surface with suction or injection in the presence of species concentration and mass diffusion has been obtained by solving the governing equations using R.K. Gill method. The fluid is assumed to be viscous, incompressible and electrically conducting with a magnetic field applied transversely to the direction of the flow. It has been observed that in the presence of mass diffusion: (i) in the case of suction, the velocity decreases and the temperature distribution and concentration of the fluid increase and for injection, the velocity increases and the temperature distribution and concentration of the fluid decrease with increase of thermal stratification parameter, (ii) in the presence of thermal stratification parameter in both the cases of suction and injection, the skin friction and rate of mass transfer decrease and the rate of heat transfer of the fluid increases with increase of chemical reaction effects, (iii) in the cases of suction and injection, an increase in the strength of magnetic field leads to fall in the velocity and rise in the temperature and concentration of the fluid along the surface. Copyright © 2003 John Wiley & Sons, Ltd.
An endochronic plasticity model for numerical simulation of industrial powder compaction processes
Authors: Khoei A. R. , Bakhshiani A. , Mofid M. 
Published: July 2003

AbstractIn this paper, the numerical modelling of powder forming process is simulated by a finite element analysis using an endochronic plasticity model. A general algorithm for the endochronic theory from the viewpoint of efficient numerical modelling is presented. Constitutive equations are established based on coupling between deviatoric and hydrostatic behaviour to the endochronic theory. Finally, the numerical schemes are examined for efficiency in the modelling of a rotational flanged‐component. It is shown how the endochronic plasticity describes the behaviour of powder material from the initial stage of compaction to final stage, in which material behaves as solid metals. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of a projection/characteristic scheme for incompressible flow
Authors: Guermond Jean‐Luc , Minev Peter D. 
Published: July 2003

AbstractThe paper presents the convergence analysis of a characteristic/projection scheme for the incompressible Navier–Stokes equations. This scheme is a modification of the scheme analysed in Achdou and Guermond (SIAM J. Numer. Anal. 2000; 37(3):799) which does not eliminate the projected velocity field from the system but rather uses it as the advecting field in the explicit characteristic advection. This field has a zero (generalized) divergence and is therefore more suitable for this purpose. It appears that this scheme has the same convergence rate as the one in Achdou and Guermond (SIAM J. Numer. Anal. 2000; 37(3):799) but on a given grid seems to produce more accurate results. The computational cost is not significantly higher since it requires only one extra inversion of the mass matrix which can be done relatively efficiently. We present numerical results which illustrate the properties of the scheme. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling damage potential of high‐frequency ground motions
Authors: Ma Guowei , Hao Hong , Lu Yong 
Published: July 2003

AbstractDamage to building structures due to underground blast‐induced ground motions is a primary concern in the corresponding determination of the safe inhabited building distance (IBD). Because of the high‐frequency nature of this category of ground motions and especially the presence of significant vertical component, the characteristics of structural response and damage differ from those under seismic type low‐frequency ground motions. This paper presents a numerical investigation aimed at evaluating reinforced concrete (RC) structure damage generated by underground blast‐induced ground excitation. In the numerical model, two damage indices are proposed to model reinforced concrete failure. A fracture indicator is defined to track the cracking status of concrete from micro‐ to macrolevel; the development of a plastic hinge due to reinforcement yielding is monitored by a plastic indicator; while the global damage of the entire structure is correlated to structural stiffness degradation represented by its natural frequency reduction. The proposed damage indices are calibrated by a shaking table test on a 1: 5‐scale frame model. They are then applied to analyse the structural damage to typical low‐ to high‐rise RC frames under blast‐induced ground motions. Results demonstrate a distinctive pattern of structural damage and it is shown that the conventional damage assessment methods adopted in seismic analysis are not applicable here. It is also found that the existing code regulation on allowable peak particle velocity of blast‐induced ground motions concerning major structural damage is very conservative for modern RC structures. Copyright © 2003 John Wiley & Sons, Ltd.
Efficiency of base isolation systems in structural seismic protection and energetic assessment
Authors: Marano Giuseppe Carlo , Greco Rita 
Published: July 2003

AbstractThis paper concerns the seismic response of structures isolated at the base by means of High Damping Rubber Bearings (HDRB). The analysis is performed by using a stochastic approach, and a Gaussian zero mean filtered non‐stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. More precisely, the generalized Kanai–Tajimi model is adopted to describe the non‐stationary amplitude and frequency characteristics of the seismic motion.The hysteretic differential Bouc–Wen model (BWM) is adopted in order to take into account the non‐linear constitutive behaviour both of the base isolation device and of the structure. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non‐linear system response in the state space. The non‐linear differential equation of the response covariance matrix is then solved by using an iterative procedure which updates the coefficients of the equivalent linear system at each step and searches for the solution of the response covariance matrix equation.After the system response variance is estimated, a sensitivity analysis is carried out. The final aim of the research is to assess the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non‐linear response, with associated large plastic displacements and, therefore, by limiting related damage phenomena in structural and non‐structural elements.In order to attain this objective the stochastic response of a non‐linear n‐dof shear‐type base‐isolated building is analysed; the constitutive law both of the structure and of the base devices is described, as previously reported, by adopting the BWM and by using appropriate parameters for this model, able to suitably characterize an ordinary building and the base isolators considered in the study.The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy. Copyright © 2003 John Wiley & Sons, Ltd.
System identification of linear structures based on Hilbert–Huang spectral analysis. Part 2: Complex modes
Authors: Yang Jann N. , Lei Ying , Pan Shuwen , Huang Norden 
Published: July 2003

AbstractA method, based on the Hilbert–Huang spectral analysis, has been proposed by the authors to identify linear structures in which normal modes exist (i.e., real eigenvalues and eigenvectors). Frequently, all the eigenvalues and eigenvectors of linear structures are complex. In this paper, the method is extended further to identify general linear structures with complex modes using the free vibration response data polluted by noise. Measured response signals are first decomposed into modal responses using the method of Empirical Mode Decomposition with intermittency criteria. Each modal response contains the contribution of a complex conjugate pair of modes with a unique frequency and a damping ratio. Then, each modal response is decomposed in the frequency–time domain to yield instantaneous phase angle and amplitude using the Hilbert transform. Based on a single measurement of the impulse response time history at one appropriate location, the complex eigenvalues of the linear structure can be identified using a simple analysis procedure. When the response time histories are measured at all locations, the proposed methodology is capable of identifying the complex mode shapes as well as the mass, damping and stiffness matrices of the structure. The effectiveness and accuracy of the method presented are illustrated through numerical simulations. It is demonstrated that dynamic characteristics of linear structures with complex modes can be identified effectively using the proposed method. Copyright © 2003 John Wiley & Sons, Ltd.
Response of structures supported on SCF isolation systems
Authors: Hamidi M. , El Naggar M. H. , Vafai A. 
Published: July 2003

AbstractAseismic base isolation is an effective method used to protect structures and their contents against earthquakes. An isolated structure may be designed to remain elastic throughout major ground motions as a result of the efficiency of the isolation systems. In this paper, the equations of motion of two‐dimensional elastic structures supported on a new base isolation system called the Sliding Concave Foundation (SCF) are presented and a procedure for their solution is suggested. The responses of a number of structures subjected to different earthquake records are evaluated and the results are compared with those of the same structures supported on two other famous isolation systems and also a fixed base condition. The results indicate the effectiveness of the SCF in protecting the supported structures even during very strong and/or long period earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluation of combination rules for peak response calculation in three‐component seismic analysis
Authors: Hernández Julio J. , López Oscar A. 
Published: July 2003

AbstractThe responses, re, given by several multicomponent combination rules used in seismic codes for determining peak responses to three ground motion components are evaluated for elastic systems and compared with the critical response rcr; this is defined as the largest response for all possible incident angles of the seismic components and obtained by means of the CQC3‐rule when a principal seismic component is vertical, or the GCQC3‐rule when it departs from the vertical direction. The combination rules examined are the SRSS‐, 30%‐, 40%‐ and IBC‐rules, considering different alternatives for the design horizontal spectrum.Assuming that a principal seismic component is along the vertical direction, the upper and lower bounds of the ratio re/rcr for each combination rule are determined as a function of the spectral intensity ratio of the horizontal seismic components and of the responses to one seismic component acting alternately along each structural axis. Underestimations and overestimations of the critical response are identified for each combination rule and each design spectrum. When a component departs from the vertical direction, the envelopes of the bounds of the ratio re/rcr for each combination rule are calculated, considering all possible values of the spectral intensity ratios. It is shown that the inclination of a principal component with respect to the vertical axis can significantly reduce the values of re/rcr with respect to the case when the component is vertical. Copyright © 2003 John Wiley & Sons, Ltd.
A simplified method of constructing fragility curves for highway bridges
Authors: Karim Kazi R. , Yamazaki Fumio 
Published: July 2003

AbstractFragility curves are found to be useful tools for predicting the extent of probable damage. They show the probability of highway structure damage as a function of strong motion parameters, and they allow the estimation of a level of damage probability for a known ground motion index. In this study, an analytical approach was adopted to develop the fragility curves for highway bridges based on numerical simulation. Four typical RC bridge piers and two RC bridge structures were considered, of which one was a non‐isolated system and the other was an isolated system, and they were designed according to the seismic design code in Japan. From a total of 250 strong motion records, selected from Japan, the United States, and Taiwan, non‐linear time history analyses were performed, and the damage indices for the bridge structures were obtained. Using the damage indices and ground motion parameters, fragility curves for the four bridge piers and the two bridge structures were constructed assuming a lognormal distribution. It was found that there was a significant effect on the fragility curves due to the variation of structural parameters. The relationship between the fragility curve parameters and the over‐strength ratio of the structures was also obtained by performing a linear regression analysis. It was observed that the fragility curve parameters showed a strong correlation with the over‐strength ratio of the structures. Based on the observed correlation between the fragility curve parameters and the over‐strength ratio of the structures, a simplified method was developed to construct the fragility curves for highway bridges using 30 non‐isolated bridge models. The simplified method may be a very useful tool to construct the fragility curves for non‐isolated highway bridges in Japan, which fall within the same group and have similar characteristics. Copyright © 2003 John Wiley & Sons, Ltd.
Active tuned liquid column damper with propellers
Authors: Chen Yung‐Hsiang , Ko Chia‐Hao 
Published: July 2003

AbstractThe active control of a Tuned Liquid Column Damper (TLCD) with two propellers is presented. A single‐degree‐of‐freedom system with a passive or active TLCD is used as an example to set up the basic equation of motion. The Optimal Control Theory is applied to establish the control law and to calculate the control force generated by these two propellers installed inside the TLCD. A simple pendulum‐like model test is carried out to study the dynamic characteristics of the passive and active TLCDs and the effectiveness of the vibrational control. Comparison of the experimental result with the analytical one shows a good agreement. Finally, the analytical results of the seismic response are also included as an example for demonstration and application. Copyright © 2003 John Wiley & Sons, Ltd.
Large earthquakes and the abandonment of prehistoric coastal settlements in 15th century New Zealand
Authors: Goff James R. , McFadgen Bruce G. 
Published: July 2003

AbstractThis paper reports on the effects of large earthquakes and related events, such as tsunamis, on prehistoric coastal settlements in New Zealand. It is based on field observations at several well‐established archaeological sites around the Cook Strait region and on literature reviews. We identify three broad periods of seismic activity in New Zealand since human occupation of the islands: 13th century, 15th century, and the 1750s to 1850s. The most significant, from a prehistoric human perspective, is the 15th century. Using examples from the Cook Strait region, we suggest that the abandonment of coastal settlements, the movement of people from the coast to inland areas, and a shift in settlement location from sheltered coastal bays to exposed headlands, was due to seismic activity, including tsunamis. We expect similar patterns to have occurred in other parts of New Zealand, and other coastal areas of the world with longer occupation histories. © 2003 Wiley Periodicals, Inc.
Depositional history and evolution of the Paso del Indio site, Vega Baja, Puerto Rico
Authors: Clark Jeffrey J. , Walker Jeff , Ramos Reniel Rodríguez 
Published: July 2003

AbstractPotshards discovered during excavation of bridge pilasters for a major expressway over the Rio Indio floodplain, a stream incised within the karsts of north‐central Puerto Rico, required large‐scale archaeological excavation. Five‐meter‐deep bridge pilaster excavations in the alluvial valley provide a 4500‐year history of deposition. Stratigraphic analysis of the exposed pilaster walls in combination with textural and organic carbon analyses of sediment cores obtained over a much broader area suggest a fluvial system dominated by overbank deposition. Six sequences of alternating light and dark layers of sediment were identified. The darker layers are largely composed of silts and clays, whereas the lighter layers are rich in sand‐sized sediment. Archaeological evidence indicates the organic‐rich dark layers, believed to be buried A horizons, coincide with pre‐historic occupation by Cedrosan Saladoid, Elenan Ostionoid, and Chican Ostionoid, extending from A.D. 450 to A.D. 1500. Lighter layers below the dark soil horizons are interpreted as overbank deposits from large magnitude flood events. The floodplain aggraded discontinuously with rapid deposition of sand followed by gradual accumulation of silt, clay, and organic material. An approximately 1‐m‐thick layer of coarse sand and gravel halfway up the stratigraphic column represents an episode of more frequent and severe floods. Based on radiocarbon ages, this layer aggraded between A.D. 1000 and A.D. 1100, which is well within the Elenan Ostionoid era (A.D. 900–1200). Rates of sedimentation during this period were approximately 8 mm per year, ten times greater than the estimates of sedimentation rates before and after this flood sequence. The cause for the change in deposition is unknown. Nonetheless the Elenan Ostionoid would have had to endure frequent loss of habitation structures and crops during these events. © 2003 Wiley Periodicals, Inc.
Geoarchaeological investigations at Studenoe, an Upper Paleolithic site in the Transbaikal Region, Russia
Authors: Buvit Ian , Waters Michael R. , Konstantinov Mikhail V. , Konstantinov Aleksander V. 
Published: July 2003

AbstractIn 1998, geoarchaeological research was carried out at the Upper Paleolithic site of Studenoe in the Transbaikal Region of Russia. The site is divided into three loci situated on two terraces overlooking the Chikoi River. Alluvial sediments beneath the oldest terrace (T2) consist of two depositional units. Radiocarbon ages indicate that aggradation of the T2 fill began before 18,000 yr B.P. Alluvial sediments beneath the lower terrace (T1) range in age from 13,000 to 10,000 yr B.P. and are divided into three depositional units. Both terraces are overlain by Holocene colluvium. Archaeological materials at Studenoe 1/1, 1/2, and 2 include dwellings, hearths, and thousands of bone and stone artifacts assigned to the late Upper Paleolithic through the Bronze Age. Evidence of microblade technology is present in all components of the site. Material from recent excavations of Paleolithic levels in the T2 fill at Studenoe includes mobiliary art, bone needles, and a large dwelling with four hearth features. © 2003 Wiley Periodicals, Inc.
Theoretical studies on structures and reactivities of organocuprate(I) and organocopper(III) species
Authors: Yamanaka Masahiro , Inagaki Akiko , Nakamura Eiichi 
Published: July 2003

AbstractSystematic evaluation of method and basis set on the structure and energetics of organocuprate(I) and organocopper(III) species has been carried out. Various structures of organocuprate(I) and organocuprate(III) complexes were optimized with the HF, MP2, and B3LYP methods, and compared with the structures determined by X‐ray crystallography (i.e., Me2Cu(I)−, (CF3)4Cu(III)−). Both the MP2 and B3LYP methods reasonably reproduce the X‐ray structures while the HF method does not. Using larger basis set and incorporating the relativistic effects for Cu afford the best results. In the studies on the energetics of a LiCu cluster model (Me2CuLi · LiCl) and Me3Cu model with the MP2, MP3, MP4DQ, MP4SDQ, CCSD(T), and B3LYP methods, the B3LYP method gives energetics similar to those obtained with the CCSD(T) method with much less cost, and hence, is judged to be the best practical method. The studies have shown that B3LYP method with the basis set incorporating the relativistic effective core potentials for Cu and the 6‐31G* basis set for the rest is the theoretical method that is the most cost‐effective for the studies of the structure and energetics of organocuprate(I) and organocopper(III) species. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1401–1409, 2003
Improved precision and efficiency of free energy calculations for small systems using λ‐scaled atomic masses and separating conformational and transformational sampling
Authors: Carlsson Peter , Nilsson Lennart 
Published: July 2003

AbstractWe present results showing the importance of appropriate treatment of atomic masses in molecular dynamics (MD)‐based single topology free‐energy perturbations (FEPs) on small molecule systems. The reversibility of gas phase simulations is significantly improved by scaling the atomic mass of mutated atoms with the λ variable normally used for the scaling of energy terms. Because this effect is less pronounced for solvated systems, it will not cancel in estimates of the relative hydration free energy difference. The advantage of mass scaling is demonstrated by a null mutation of ethane to ethane and the calculation of the relative hydration free energy difference between ethane and n‐propane. Furthermore, it is found that the simulation time necessary for converged MD/FEPs is prohibitively large for relative hydration free energy calculations on cyclic alkanes. Therefore, we explore an alternative free energy pathway including strongly constrained conformations to improve convergence in FEP simulations of flexible molecules. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1383–1389, 2003
Exploring potential energy surfaces for chemical reactions: An overview of some practical methods
Authors: Schlegel H. Bernhard 
Published: July 2003

AbstractPotential energy surfaces form a central concept in the application of electronic structure methods to the study of molecular structures, properties, and reactivities. Recent advances in tools for exploring potential energy surfaces are surveyed. Methods for geometry optimization of equilibrium structures, searching for transition states, following reaction paths and ab initio molecular dynamics are discussed. For geometry optimization, topics include methods for large molecules, QM/MM calculations, and simultaneous optimization of the wave function and the geometry. Path optimization methods and dynamics based techniques for transition state searching and reaction path following are outlined. Developments in the calculation of ab initio classical trajectories in the Born‐Oppenheimer and Car‐Parrinello approaches are described. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1514–1527, 2003