bluuebunny/crossref_metadata_2025_split huggingface dataset:
The hippocampus and caudomedial neostriatum show selective responsiveness to conspecific song in the female zebra finch
Authors: Bailey David J. , Rosebush Julia C. , Wade Juli 
Published: October 2002

AbstractThe perception of song is vital to the reproductive success of both male and female songbirds. Several neural structures underlying this perception have been identified by examining expression of immediate early genes (IEGs) following the presentation of conspecific or heterospecific song. In the few avian species investigated, areas outside of the circuit for song production contain neurons that are active following song presentation, specifically the caudal hyperstriatum ventrale (cHV) and caudomedial neostriatum (NCM). While studied in detail in the male zebra finch, IEG responses in these neural substrates involved in song perception have not been quantified in females. Therefore, adult female zebra finches were presented with zebra finch song, nonzebra finch song, randomly generated tones, or silence for 30 min. One hour later they were sacrificed, and their brains removed, sectioned, and immunocytochemically processed for FOS expression. Animals exposed to zebra finch song had a significantly higher density of FOS‐immunoreactive cells in the NCM than those presented with other songs, tones, or silence. Neuronal activation in the cHV was equivalent in birds that heard zebra finch and non‐zebra finch song, expression that was higher than that observed in the groups that heard no song. Interestingly, the hippocampus (HP) and adjacent parahippocampal area (AHP) were activated in a manner comparable to the NCM. These results suggest a general role for the cHV in song perception and a more specific role for the NCM and HP/AHP in facilitating recognition of and responsiveness to species‐specific song in female zebra finches. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 43–51, 2002
Pre‐ and postsynaptic mechanisms in Hebbian activity‐dependent synapse modification
Authors: Li Min‐Xu , Jia Min , Yang Li‐Xia , Dunlap Veronica , Nelson Phillip G. 
Published: October 2002

AbstractWe have used a three compartment tissue culture system that involved two separate populations of cholinergic neurons in the side compartments that converged on a common target population of myotubes in the center compartment. Activation of the axons from one population of neurons produced selective down‐regulation of the synaptic inputs from the other neuronal population (when the two inputs innervated the same myotubes). The decrease in heterosynaptic inputs was mediated by protein kinase C (PKC). An activity‐dependent action of protein kinase A (PKA) was associated with the stimulated input and this served to selectively stabilize this input. These changes associated with PKA and PKC activation were mediated by alterations in the number of acetylcholine receptors at the neuromuscular junction. These results suggest that neuromuscular electrical activity produces postsynaptic activation of both PKA and PKC, with the latter producing generalized synapse weakening and the former a selective synapse stabilization. Treatment of the neuronal cell body and axon to increase PKC activity by putting phorbal ester (PMA) in the side chamber did not affect synaptic transmission (with or without stimulation). By contrast, PKA blockade in the side compartment did produce an activity‐dependent decrease in synaptic efficacy, which was due to a decrease in quantal release of neurotransmitter. Thus, when the synapse is activated, it appears that presynaptic PKA action is necessary to maintain transmitter output. Published 2002 Wiley Periodicals, Inc. J Neurobiol 52: 241–250, 2002
An interactive geometry utility environment for multi‐disciplinary computational engineering
Authors: Zheng Yao , Weatherill Nigel P. , Turner‐Smith Edward A. 
Published: October 2002

AbstractA parallel simulation user environment (PSUE) has been developed for unstructured grid‐based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi‐disciplinary engineering analysis capability within one unified computational framework. It provides an enhanced capability for complex and multiple problem definition, a graphics environment for guidance through the grid generation process with visual validation of each step, and robust and computationally efficient unstructured grid generation modules. This paper addresses an interactive geometry utility environment (IGUE), which is the primary part of the PSUE, providing sophisticated graphical user interfaces with geometric handling capability oriented to the unstructured grid technology. The IGUE is equipped with windowing functionality from the X‐Window system, and its underpinning data structure is based on non‐manifold topology. Copyright © 2001 John Wiley & Sons, Ltd.
An implicit method for the analysis of transient flows in pipe networks
Authors: Greyvenstein G. P. 
Published: October 2002

AbstractExisting methods for the analysis of transient flows in pipe networks are often geared towards certain types of flows such as gas flows vis‐à‐vis liquid flows or isothermal flows vis‐à‐vis non‐isothermal flows. Also, simplifying assumptions are often made which introduce inaccuracies when the method is applied outside the domain for which it was originally intended. This paper describes an implicit finite difference method based on the simultaneous pressure correction approach which is valid for both liquid and gas flows, for both isothermal and non‐isothermal flows and for both fast and slow transients. The problematic convective acceleration term in the momentum equation, often neglected in other methods, is retained but eliminated by casting the momentum equation in an alternative form. The accuracy and stability of the method, depending on a time‐step weighing factor α, are illustrated by analysing fast transients in a pipeline and simple branching network. The proposed method compares very well with the second‐order‐method of characteristics and the two‐step Lax–Wendroff method. The advantages of the present method is its speed over a range of problems including both fast and slow transients, its accuracy, its stability and its flexibility. Copyright © 2001 John Wiley & Sons, Ltd.
Finite horizon H∞ filter and its 2N algorithm
Authors: Wu Z. G. , Leung A. Y. T. , Zhong W. X. 
Published: October 2002

AbstractA 2N algorithm will double a time (or space) step in each evaluation for initial value problem. The 2N algorithm for the integration of filtering differential equation of the finite horizon H∞ filter is presented in this paper. Since it is a boundary value problem within a time range, a new 2N algorithm is introduced by merging two intervals each time so that the time interval is doubled in each evaluation. If one divides the original time range into one million intervals, 20 evaluations will complete the whole process. Owing to the extremely small initial time interval, the first few terms of the Taylor expansion of the interval matrices are sufficient for very accurate results. Since the filter gain matrices are the solution of the Riccati differential equation and the existence of the solution depends on the induced norm γ, the computation of critical value γ is reviewed first. Then, according to the result and the prespecified performance index, the suitable parameter γ−2 can be selected and the precise numerical solution of the Riccati differential equation and the filtering differential equation can be obtained by using the 2N algorithm, although the filtering equation is time varying. The 2N algorithm for interval merging is given explicitly. Copyright © 2001 John Wiley & Sons, Ltd.
Hat interpolation wavelet‐based multi‐scale Galerkin method for thin‐walled box beam analysis
Authors: Kim Yoon Young , Jang Gang‐Won 
Published: October 2002

Abstract The objective of the present work is to propose a new adaptive wavelet‐Galerkin method based on the lowest‐order hat interpolation wavelets. The specific application of the present method is made on the one‐dimensional analysis of thin‐walled box beam problems exhibiting rapidly varying local end effects. Higher‐order interpolation wavelets have been used in the wavelet‐collocation setting, but the lowest‐order hat interpolation is applied here first and a hat interpolation wavelet‐based Galerkin method is newly formulated. Unlike existing orthogonal or biorthogonal wavelet‐based Galerkin methods, the present method does not require special treatment in dealing with general boundary conditions. Furthermore, the present method directly works with nodal values and does not require special formula for the evaluation of system matrices. Though interpolation wavelets do not have any vanishing moment, an adaptive scheme based on multi‐resolution approximations is possible and a preconditioned conjugate gradient method can be used to enhance numerical efficiency. Copyright © 2001 John Wiley & Sons, Ltd.
Simulating the propagation of displacement discontinuities in a regularized strain‐softening medium
Authors: Wells G. N. , Sluys L. J. , de Borst R. 
Published: October 2002

AbstractA numerical model is developed which allows the inclusion of displacement discontinuities in a strain‐softening medium, independent of the finite element mesh structure. Inelastic deformations develop in the continuum and, when a critical threshold of inelastic deformation is reached, a displacement discontinuity is inserted. Discontinuities are introduced using the partition of unity concept which allows discontinuous functions to be added to the standard finite element basis. It is shown that the introduction of displacement discontinuities at the later stages of the failure process can lead to a failure mode that is fundamentally different than that using a continuum model only. This combined continuum‐discontinuous model is better able to describe the entire failure process than a continuum or a discrete model alone and treats mode‐I and mode‐II failure in a unified fashion. Copyright © 2001 John Wiley & Sons, Ltd.
A posteriori error estimation in non‐linear FE analyses of shell structures
Authors: Lackner R. , Mang H. A. 
Published: October 2002

AbstractDuring the last decade, significant scientific efforts were made in the area of quality assurance of numerical results obtained by means of the finite element method (FEM). These efforts were based on adaptive remeshing controlled by an estimated error. This paper reports on the extension of error estimation to non‐linear shell analysis involving strain‐hardening and softening plasticity. In the context of incremental‐iterative analyses, an incremental error estimator is introduced. It is based on the rate of work. The stress recovery technique proposed by Zienkiewicz and Zhu (Int. J. Numer. Meth. Engng 1992; 33:1331) is modified to allow for discontinuities of certain stress components in case of localization arising from, e.g. cracking of concrete. The developed error estimator is part of a calculation scheme for adaptive non‐linear FE analysis. If the estimated error exceeds a prespecified threshold value in the course of an adaptive analysis, a new mesh is generated. After mesh refinement the state variables are transferred from the old to the new mesh and the calculation is restarted at the load level which was attained with the old mesh. The performance of the proposed error estimator is demonstrated by means of adaptive calculations of a reinforced concrete (RC) cooling tower. The influence of the user‐prescribed error threshold on the numerical results is investigated. Copyright © 2002 John Wiley & Sons, Ltd.
p‐Version interface elements in global/local analysis
Authors: Schiermeier John E. , Kansakar Rajendra , Mong Dao , Ransom Jonathan B. , Aminpour Mohammad A. , Stroud W. Jefferson 
Published: October 2002

AbstractWhen performing global/local analysis, the issue of connecting dissimilar meshes often arises, especially when refinement is performed. One method of connecting these dissimilar meshes is to use interface elements. Curve interface elements, to connect dissimilarp‐element edges along a curve; surface interface elements, to connect dissimilarp‐element faces over a surface; and shell‐to‐solid transition interface elements, to connect dissimilarp‐element edges withp‐element faces, have been implemented in MSC.Nastran. The background, theory, and implementation are being presented herein, along with examples. These three interface elements comprise a complete set of interface tools for global/local analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Testing the asymptotic behaviour of shell elements—Part II: New limit tests: analytical solutions and the RFNS element case
Authors: Briassoulis D. 
Published: October 2002

AbstractThe asymptotic behaviour of classical benchmark tests was investigated in the first part of this work. In the present second part, the behaviour of some new limit problems, recently proposed as being specifically applicable to benchmark testing of the asymptotic behaviour of shell elements, is analytically and numerically investigated. Exact analytical solutions are obtained based on Flugge's theory for cylindrical shells. These analytical solutions are used along with, and in comparison to, the corresponding solutions obtained earlier by symbolic calculus using the Reissner–Mindlin shell model. The reformulated four‐node shell (RFNS) element is employed in the numerical analyses in a parallel, supportive–comparative character, next to the analytical investigation of the asymptotic behaviour of the new limit tests. As with the case of the classical benchmark tests, in the course of the numerical investigation, the reliability and efficiency of the RFNS element is re‐confirmed in all cases of the new asymptotic tests. A good agreement with the boundary layers described analytically is obtained even in very thin shell element applications. The various load‐carrying mechanisms shown numerically to be active in the cases under investigation follow closely the analytical predictions. The energy components appear to be more sensitive to the modelling of boundary layers in cases of mixed mode problems. In several cases, the solutions obtained earlier by using symbolic calculus are shown to be inadequate. Copyright © 2002 John Wiley & Sons, Ltd.
Genetic optimization of stiffened plates without the FE mesh support
Authors: Marcelin J. L. 
Published: October 2002

AbstractThis paper deals with the optimization of beam stiffeners on plates by varying their positions in order to minimize the maximum deflection of the plate. Genetic algorithms are used. The research strategy consists in substituting, for finite element calculations in the optimization process, an approximate response of a neural network, or an approximate response from a Ritz method. This paper shows how it is possible to deal with more important problems and to envisage more general baseline design for stiffened plates by adding the orientation angle of each stiffener as a design variable. This paper also shows how one can free oneself from the FE mesh, i.e. how one no longer needs the support of the mesh for the stiffeners. Copyright © 2002 John Wiley & Sons, Ltd.
Boundary element analysis of reinforced shear deformable shells
Authors: Wen P. H. , Aliabadi M. H. , Young A. 
Published: October 2002

AbstractIn this paper, stiffened shear‐deformable shells are analysed using the boundary element method. Coupled boundary integral equations are presented for describing curved shells under general loading conditions. The equations are based on boundary integral equations for plane stress and plate bending, with coupling terms arising from the curvature of the shell. Domain integrals are transformed into boundary integrals using the dual reciprocity technique. Stiffeners are modelled as curved beams, continuously attached to the shell. Numerical solutions calculated using the present method are compared with finite element results in two examples. Copyright © 2002 John Wiley & Sons, Ltd.
A hybrid topology optimization algorithm for static and vibrating shell structures
Authors: Belblidia F. , Bulman S. 
Published: October 2002

AbstractStructural designers are reconsidering traditional design procedures using structural optimization techniques. Although shape and sizing optimization techniques have facilitated a great improvement in the emergence of new optimum designs, they are still limited by the fact that a suitable topology must be assumed initially. In this paper a hybrid algorithm entitled constrained adaptive topology optimization, or CATO is introduced. The algorithm, based on an artificial material model and an adaptive updating scheme, combines ideas from the mathematically rigorous homogenization (h) methods and the intuitive evolutionary (e) methods. The algorithm is applied to shell structures under static or free vibration situations. For the static situation, the objective is to produce the stiffest structure subject to given loading conditions, boundary conditions and material properties. For the free vibration situation, the objective is to maximize or minimize a chosen frequency. In both cases, a constraint on the structural volume/mass is applied and the optimization process is achieved by redistributing the material through the shell structure. The efficiency of the proposed algorithm is illustrated through several numerical examples of shells under either static or free vibration situations. Copyright © 2002 John Wiley & Sons, Ltd.
New superconvergent points of the 8‐node serendipity plane element for patch recovery
Authors: Liew K. M. , Rajendran S. 
Published: October 2002

AbstractThe Gaussian quadrature points, which are generally observed to be the same as the Barlow points for lower order elements, have so far been used as the sampling points for the superconvergent patch recovery (SPR). Recent developments on the best‐fit method to calculate the optimal sampling points suggest that, for higher order elements, Barlow points need not be the optimal sampling points and also need not be the same as the Gaussian quadrature points. In this paper the best‐fit method is extended to predict the optimal points of the 8‐node serendipity rectangular element, and it is observed that best‐fit points do not exist. Next, a novel method is proposed, in which, the expressions for stress‐error based on the best‐fit are used in the least‐square fit of the patch recovery, and thereby the superconvergent points are obtained more directly. Application of this method to the 8‐node serendipity element reveals the existence of two sets of superconvergent points for patch recovery, one of which is the well‐known Gaussian points, ( $ \pm 1/\sqrt 3 , \pm 1/\sqrt 3 $), and the other is the set of four points given by $\{ (0, \pm \sqrt {2/3} ),\,( \pm \sqrt {2/3} ,0)\}$, the existence of which has not been known before. A detailed numerical study on the patch recovery of stresses for two demonstrative problems reveals that there indeed exist two sets of superconvergent points as predicted by the proposed method. The comparative performance of the two sets of points is tested for typical demonstrative problems and the results are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Inverse problems for estimating bottom boundary conditions of natural waters
Authors: de Campos Velho Haroldo F. , Retamoso Mario R. , Vilhena Marco Tulio M. B. 
Published: October 2002

Abstract Unknown boundary conditions for natural waters are estimated using an inverse problem methodology. In the formulation of the inverse problem, expressed as a non‐linear constrained optimization problem, its objective function is given by a square difference term, between experimental and computed data, added to a regularization operator. The computed data are obtained by solving the radiative transfer direct problem using the LTSN method. A key aspect to get a good reconstruction is played by observed data quality. The reconstruction strategy is examined for in situ radiance and irradiance data for many arrangements of the experimental grid of the measurement devices, in order to plan good designs for experimental works. Copyright © 2002 John Wiley & Sons, Ltd.
Linear multi‐model time‐optimization
Authors: Boltyanski V. , Poznyak A. 
Published: October 2002

AbstractA linear optimization problem with unknown parameters from a given finite set is tackled. The problem is to find therobust time‐optimal controltransferring a given initial point to a convex terminal compact setMforallunknown parameters in a shortest time. The robust maximum principle for this minimax problem is formulated. It gives a necessary and sufficient condition of robust optimality. Under natural conditions, the existence and uniqueness of robust optimal controls are proven when the resource set is a convex polytope. Several illustrating examples, including a bang–bang robust optimal control, are considered in detail. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation into new materials for optical devices: the miscibility and solvent effects of azobenzene derivative blends
Authors: Sharma Lakshmi , Kimura Tatsumi , Matsuda Hiro 
Published: October 2002

AbstractWith the increasing demand for novel devices with optical applications the search for new materials to data store and process becomes a priority. By introducing blends, tailor made properties and low cost give added advantage. Miscibility is an essential requirement for a new material, this research thus involves miscibility studies of poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)90‐co‐(methyl methacrylate)10, (azobenzene derivative) with polymethyl‐methacrylate (PMMA), polyvinylacetate (PVAc) and polyvinylchloride (PVC) prepared in tetrahydrofuran (THF), and/or dimethylformamide (DMF) and/or dichloromethane (CH2Cl2). The glass transitions, solvent and varying molecular weight effect were investigated, since these all primarily influence the miscibility. THF was found to encourage miscibility at specific compositions of PVAc and PVC blends. However, with CH2Cl2 and DMF immiscibility is encouraged. The Fox–Flory equation was applied to the blends analyzing the PVC blends in DMF as deviations from ideality. Different molecular weights of PMMA were identified as immiscible regardless of solvent. PMMA's lower solubility in THF and CH2Cl2 compared to the azobenzene derivative, displayed the existence of PMMA islands. In all blends the favorable and unfavorable interactions between polymer–solvent–polymer systems are considered. Furthermore, the miscibility effect on increasing the MMA content of the azobenzene derivative was also investigated. Copyright © 2002 John Wiley & Sons, Ltd.