Component Substructures Research Articles

Evaluation of Different Contact Assumptions in the Analysis of Friction-Induced Vibrations Using Dynamic Substructuring

Dynamic substructuring methods are initially developed for time-invariant systems to evaluate the dynamic behavior of a complex structure by coupling the component substructures. Sometimes, the component substructures change their position over time, affecting the dynamics of the entire structure. This family of problems can be tackled using substructuring techniques by isolating the time dependency in the coupling conditions among the time-invariant substructures. Mechanical systems, composed of subsystems in relative motion with a sliding interface, can be analyzed using this approach. In previous work, the authors proposed a solution method in the time and frequency domain using this approach under the assumption that the relative sliding motion at the contact interfaces is a-priori known, at least approximately. This assumption implies that the perturbation generated by the friction-induced vibration is neglected. In subsequent work, a more realistic contact assumption was considered to account also for the local vibration of the contact point and the geometric nonlinearity due to the elastic deformation. In this paper, a simplification with respect to the realistic contact assumption is introduced, which neglects the angular variation of the direction normal to the contact interface. The simplified approach is advantageous because it is equally able to highlight the occurrence of friction-induced instabilities, and it reduces the computational burden. The results of the substructuring methods using different contact assumptions are compared with those of a reference numerical method to show how the choice of the contact algorithm allows for tackling a wide range of operating conditions, from simple position-dependent problems up to complex friction-induced vibration phenomena.

Friction-induced vibrations in the framework of dynamic substructuring

In complex vibrating systems, contact and friction forces can produce a dynamic response of the system (friction-induced vibrations). They can arise when different parts of the system move one with respect to the other generating friction force at the contact interface. Component mode synthesis and more in general substructuring techniques represent a useful and widespread tool to investigate the dynamic behavior of complex systems, but classical techniques require that the component subsystems and the coupling conditions (compatibility of displacements and equilibrium of forces) are time invariant. In this paper, a substructuring method is proposed that, besides accounting for the macroscopic sliding between substructures, is able to consider also the local vibrations of the contact points and the geometric nonlinearity due to the elastic deformation, by updating the coupling conditions accordingly. This allows to obtain a more reliable model of the contact interaction and to analyze friction-induced vibrations. Therefore, the models of the component substructures are time invariant, while the coupling conditions become time dependent and a priori unknown. The method is applied to the study of a finite element model of two bodies in frictional contact, and the analysis is aimed to the validation of the proposed method for the study of dynamic instabilities due to mode coupling.

The representation features of the personal experience substructures of students with different self-concept profiles

The article is devoted to the substructures of the personal component of individual experience research. In the framework of theoretical analysis, the structural organization of individual experience is reviewed. The author's position consists in sticking to the O.M. Laktionov three-component model of the experience.
 During the theoretical analysis contemporary studies devoted to the study of individual experience are reviewed. Several substructures of the personal component of individual experience, that require attentive study, are defined. The self-concept notion is analyzed. For the first time, an analysis of the features of relationship between the feeling of self-concept well-being and the personal experience substructures are presented.
 The analysis, described in this article, is a continuation of the research, which devoted to the study of self-concept in the framework of the structure of the students` personal component of individual experience, during which on the basis of analysis the substructures of personal experience formation features the self-concept profiles were received. Four self-concept profiles were taken into consideration out of the results of the study: the "Conflict profile": persons for whom the simultaneous inclusion of the prosperous and problematic types of self-perception is inherent; "Prosperous profile": persons for whom the prosperous self-concept perception, that combines with low level of problem self-concept perception, is inherent; "Tendency to well-being": persons who are characterized by the tendency to decrease the negative evaluation of their self-concept, having the average indicators of their self-concept well-being; "Tendency to conflict": individuals, who are characterized by average indicators of their self-concept perception in a problematic context in a tendency to decrease the assessment of their self-concept well-being.
 Directly in the course of the work, described in the article, a comparative analysis of students with different profiles was performed, that was based on the degree of representation of individual experience personal component substructures. The comparison was made using the rank criterion of Kruskal-Wallis.
 During the comparison, the following results were obtained: for the students with different self-concept profiles was not revealed any differences in the indicators of self-esteem, neuroticism, extraversion, cooperation, conscientiousness, planning self-regulation, self-regulation flexibility, goal purpose in life orientation, and such values as conformance, traditions, kindness, universality and security. Openness to experience, modeling, results estimation, independence, general level of self-regulation, process and result orientation, locus of control myself, general life meaningfulness and independence as a value were the most expressive for students with a prosperous self-concept profile, and the least expressive – for students with a conflict profile and profile with a tendency to conflict. Programming, as well as the stimulation, achievement and power values were the most expressive for the students with a tendency to a prosperous self-perception. The locus of life control and hedonism as the value was found the most expressive among the students with a tendency to a conflict in their own self-perception; the least expressive it was for students with a prosperous profile.

An approach for elastodynamic modeling of hybrid robots based on substructure synthesis technique

Parallel kinematic machines exhibit strong pose-dependent static and dynamic behaviors, which makes accurate and rapid compliance analysis over the entire workspace an important issue in the design optimization. This paper presents a general approach for elastodynamic modeling of parallel kinematic machines using substructure synthesis technique. Firstly, the whole system is decomposed into two groups of substructures, i.e. component substructures and joint substructures. Then, the degrees of freedom of component substructures are reduced using modal reduction technique, and joint substructures are modeled by virtual springs with contact stiffness between adjacent component substructures. Finally, two threads are merged at junction surfaces to offer the equations of motion of the system as a whole, allowing the static and dynamic performances to be rapidly predicted with sufficient accuracy. The dynamic model of a 5-DOF hybrid robot is developed using the proposed method and the computational results show that rigidity and lower mode natural frequencies over the workspace match well with those obtained by the full finite element analysis.

Innovative substructure approach to estimating structural parameters of shear structures

An innovative substructure approach is proposed for estimating the structural parameters of shear structures from the acceleration responses of individual substructures. Two parallel methods are created to form single-degree-of-freedom models of each substructure. The behavioral characteristics of these substructure models chiefly depend on the structural parameters of the edges of the component substructure, which is separate from the shear structure. To obtain structural parameters from the substructure accelerations, discrete substructure models with accelerations are generated using Newmark's method and are found similar to the autoregressive moving average with exogenous (ARMAX) inputs models. Sophisticated techniques for solving ARMAX models are used to process the accelerations and to extract the structural parameters of the substructures. A linear relationship among model coefficients of the discrete substructure models and ARMAX models is discovered that provides an accurate and simple way to identify all the substructure parameters. A numerical simulation of a 10-story shear structure during earthquake is performed to verify this substructure approach, where the factors of the size of the substructure and the noise disturbance are considered. Finally, this substructure approach is used to identify a structural model and reproduce the structural responses of a five-story three-dimensional structure in a shaking-table experiment.

Bootstrapping language acquisition

The semantic bootstrapping hypothesis proposes that children acquire their native language through exposure to sentences of the language paired with structured representations of their meaning, whose component substructures can be associated with words and syntactic structures used to express these concepts. The child’s task is then to learn a language-specific grammar and lexicon based on (probably contextually ambiguous, possibly somewhat noisy) pairs of sentences and their meaning representations (logical forms).Starting from these assumptions, we develop a Bayesian probabilistic account of semantically bootstrapped first-language acquisition in the child, based on techniques from computational parsing and interpretation of unrestricted text. Our learner jointly models (a) word learning: the mapping between components of the given sentential meaning and lexical words (or phrases) of the language, and (b) syntax learning: the projection of lexical elements onto sentences by universal construction-free syntactic rules. Using an incremental learning algorithm, we apply the model to a dataset of real syntactically complex child-directed utterances and (pseudo) logical forms, the latter including contextually plausible but irrelevant distractors. Taking the Eve section of the CHILDES corpus as input, the model simulates several well-documented phenomena from the developmental literature. In particular, the model exhibits syntactic bootstrapping effects (in which previously learned constructions facilitate the learning of novel words), sudden jumps in learning without explicit parameter setting, acceleration of word-learning (the “vocabulary spurt”), an initial bias favoring the learning of nouns over verbs, and one-shot learning of words and their meanings. The learner thus demonstrates how statistical learning over structured representations can provide a unified account for these seemingly disparate phenomena.

Poetry and narrative: an evolutionary perspective on the cognition of verbal art

The study of the aesthetic genres reveals important design features of cognition, in how complex higher-order abilities are organized mentally. An evolutionary perspective frames this research in a way that considers the componential nature of language-related abilities in particular. In addition, it directs our attention to the important problem of understanding how different abilities are related. In this review of the research the focus will be on poetic and narrative abilities: (1) as they develop in children, (2) how the component sub-structures of poetry and narrative might be represented cognitively, and (3) how they may have emerged in early humans. Crucially, the analysis of component structures implies understanding how they interact in performance, and more interestingly how different abilities and faculties share competence modules and processing mechanisms in common. This approach helps put the discussion regarding the relative weight of domain-specific and domain-general structures into perspective, potentially reconciling some seemingly opposing viewpoints in evolutionary science and in the study of language development.

Atomic force microscopy in imaging of viruses and virus-infected cells.

Atomic force microscopy (AFM) can visualize almost everything pertinent to structural virology and at resolutions that approach those for electron microscopy (EM). Membranes have been identified, RNA and DNA have been visualized, and large protein assemblies have been resolved into component substructures. Capsids of icosahedral viruses and the icosahedral capsids of enveloped viruses have been seen at high resolution, in some cases sufficiently high to deduce the arrangement of proteins in the capsomeres as well as the triangulation number (T). Viruses have been recorded budding from infected cells and suffering the consequences of a variety of stresses. Mutant viruses have been examined and phenotypes described. Unusual structural features have appeared, and the unexpectedly great amount of structural nonconformity within populations of particles has been documented. Samples may be imaged in air or in fluids (including culture medium or buffer), in situ on cell surfaces, or after histological procedures. AFM is nonintrusive and nondestructive, and it can be applied to soft biological samples, particularly when the tapping mode is employed. In principle, only a single cell or virion need be imaged to learn of its structure, though normally images of as many as is practical are collected. While lateral resolution, limited by the width of the cantilever tip, is a few nanometers, height resolution is exceptional, at approximately 0.5 nm. AFM produces three-dimensional, topological images that accurately depict the surface features of the virus or cell under study. The images resemble common light photographic images and require little interpretation. The structures of viruses observed by AFM are consistent with models derived by X-ray crystallography and cryo-EM.

A motif-based analysis of glycan array data to determine the specificities of glycan-binding proteins

Glycan arrays have enabled detailed studies of the specificities of glycan-binding proteins. A challenge in the interpretation of glycan array data is to determine the specific features of glycan structures that are critical for binding. To address this challenge, we have developed a systematic method to interpret glycan array data using a motif-based analysis. Each glycan on a glycan array is classified according to its component sub-structures, or motifs. We analyze the binding of a given lectin to each glycan in terms of the motifs in order to identify the motifs that are selectively present in the glycans that are bound by the lectin. We compared two different methods to calculate the identification, termed intensity segregation and motif segregation, for the analysis of three well-characterized lectins with highly divergent behaviors. Both methods accurately identified the primary specificities as well as the weaker, secondary specificities of all three lectins. The complex binding behavior of wheat germ agglutinin was reduced to its simplified, independent specificities. We compiled the motif specificities of a wide variety of plant lectins, human lectins, and glycan-binding antibodies to uncover the relationships among the glycan-binding proteins and to provide a means to search for lectins with particular binding specificities. This approach should be valuable for rapidly analyzing and using glycan array data, for better describing and understanding glycan-binding specificities, and as a means to systematize and compare data from glycan arrays.

A composite modulated structure mechanism for Ag + fast ion conduction in pearceite and polybasite mineral solid electrolytes

A careful electron diffraction investigation of pearceite- Tac and polybasite- Tac samples in the Ag + fast ion conducting state reveals that the average hexagonal [Ag I 9] 9+ sub-structure in these mineral solid electrolyte systems is mutually incommensurable with respect to the remaining [(Ag I,Cu I) 6(As III,Sb III) 2S 7] 2−[Cu IS 4] 7− framework sub-structure. It is shown how the mutual incommensurability of the two component sub-structures can be compatible with crystal chemical commonsense, with previously reported average structure refinements of these phases as well as providing an insight into their Ag + fast ion conductivity at such low temperatures. In addition, Ag +/Cu + ion ordering (and associated displacive shifts of the centreing S 2− ions) in the S 2−(Ag,Cu) 6 octahedral sites is shown to provide a mechanism for low temperature superstructure ordering.

Effect of uncertainties on substructure coupling: Modelling and reduction strategies

Different strategies for modelling and reducing the effect of uncertainties on the dynamic behaviour of coupled structures are discussed in this paper. In assembled structures, each component satisfies specifications about material properties and dimensional tolerances. Variability of design specifications within the tolerance field may affect the dynamic behaviour of the assembled structure more than that of any individual component substructure. Among modelling strategies, non-predictive techniques such as post-processing of data from a set of randomly assembled structures and analysis of sensitivities to uncertain variables are considered. However, emphasis is placed on a less trivial yet simple strategy such as the use of design of experiments to fit a regression model. Different reduction strategies are considered according to whether small design changes (even revised tolerance allocation) are still possible or not. In the latter case, selective assembly is extended to problems where the performance requirement is not the clearance between two parts, but a prescribed dynamic behaviour.

FE‐Model Reduction for FE‐BE Coupling with Large Fluid‐Structure Interfaces

For the finite element method model, reduction techniques exist to represent the dynamic behavior of component substructures. Depending on the type of reduction method, the reduction basis contains constraint or attachment modes, which are computed for all structural degrees of freedom on an interface. The interface can either be defined by adjacent substructures or by coupling interfaces to other physical domains, as it is the case for FE‐BE coupled systems. A large interface thus leads to an increased size of the reduced order model and limits standard model reduction techniques to applications with small interfaces. In this work, interface reduction methods are investigated. Here, the size of the reduced order model is decreased by reducing the number of retained interface modes, while marginally increasing the reduction error. A direct reduction method based on strain‐‐energy considerations is presented. Additionally, an iterative reduction scheme is proposed which only adds a basis vector to the redu...

Enhanced Bridge Replacement Cost Models for Indiana's Bridge Management System

Bridge managers have a duty to monitor and update the costs of bridge preservation activities and to implement cost-effective actions that are in the best interests of taxpayers. This paper presents details of replacement cost modeling for each bridge component (superstructure, substructure, approach, and other costs) for bridges with concrete slab, concrete beam, or steel superstructures. This was done with recent bridge construction data on the Indiana state highway network. It was determined that costs other than substructure and superstructure costs accounted for more than one-half of total replacement cost. The present study supports earlier studies by asserting that basic bridge characteristics such as type, length, and deck area may generally be used to derive reliable estimates of bridge replacement costs. The study also shows that economies of scale can play a significant role in reliable bridge cost estimation. It was determined that the average overall unit cost of replacement for steel superstructure bridges was generally lower than that for concrete superstructure bridges. It was seen that differences in replacement costs across bridge types are attributable not necessarily to cost differences in material and construction procedure only but also to economy-of-scale effects. Cost models can be used to predict total costs of future bridge replacements and are therefore useful for vital bridge management functions such as needs assessments, budgeting, and programming.

Enhanced Bridge Replacement Cost Models for Indiana's Bridge Management System

Bridge managers have a duty to monitor and update the costs of bridge preservation activities and to implement cost-effective actions that are in the best interests of taxpayers. This paper presents details of replacement cost modeling for each bridge component (superstructure, substructure, approach, and other costs) for bridges with concrete slab, concrete beam, or steel superstructures. This was done with recent bridge construction data on the Indiana state highway network. It was determined that costs other than substructure and superstructure costs accounted for more than one-half of total replacement cost. The present study supports earlier studies by asserting that basic bridge characteristics such as type, length, and deck area may generally be used to derive reliable estimates of bridge replacement costs. The study also shows that economies of scale can play a significant role in reliable bridge cost estimation. It was determined that the average overall unit cost of replacement for steel superstructure bridges was generally lower than that for concrete superstructure bridges. It was seen that differences in replacement costs across bridge types are attributable not necessarily to cost differences in material and construction procedure only but also to economy-of-scale effects. Cost models can be used to predict total costs of future bridge replacements and are therefore useful for vital bridge management functions such as needs assessments, budgeting, and programming.

On highly convergent 2D acoustic and elastic wave propagation models

AbstractThe presented approach for reducing the phase and group errors in short wavelength pulses propagation modelling is based upon modal error minimization. A computational model is built of component substructures (CS) the matrices of which are obtained by modal synthesis. The necessary modal properties of CS are established by solving the cumulative modal error minimization problem for a sample domain the exact modal frequencies of which are known theoretically. Earlier the approach has been demonstrated to work well in 1D case. In this work the results for 2D rectangular meshes describing elastic and/or acoustic wave propagation have been obtained. As a result, models having up to 80% of modal frequencies with an error less than 2% can be obtained by using the optimized component substructures. Though the synthesized mass matrices are non‐diagonal, the obtained dynamic models are able to simulate short transient waves and wave pulses propagating in elastic or acoustic environments by using only a few nodal points per pulse length. Copyright © 2005 John Wiley & Sons, Ltd.

The Conceptual Structure of German Impersonal Constructions

German impersonal constructions manifest an array of morphosyntactic properties, such as so-called expletive dummy subjects, 3rd person singular verb agreement, and, in some cases, experiencer nominals bearing “quirky” case (usually dative), that have traditionally been regarded as purely accidental, idiosyncratic, or semantically vacuous. This article argues that these properties typically associated with impersonal constructions in German can be semantically motivated and explained within the theoretical framework of Cognitive Grammar (see Langacker 1987a, 1991a, 1991b). Within this framework, it is assumed that morphosyntactic markers are meaningful and polysemous: they are complex conceptual categories with distinct but related senses radiating from a prototypical sense. As a result, impersonal constructions and their component substructures are seen to be meaningful in their own right in reflecting a particular way of construing a scene, rather than as epiphenomena of autonomous syntactic processes.I would like to acknowledge the perceptive and helpful feedback of the anonymous JGL reviewers. I have tried to follow their suggestions wherever possible. Of course, I take full responsibility for any errors or lack of clarity that may remain.

Parametric Study of Coupled Wall Behavior—Implications for the Design of Coupling Beams

Coupled walls are known to be efficient lateral load resisting systems; however, the relationship between their global and local behavior is not well understood and has been shown to result in structural systems having excessive internal deformation or strength demands on their component substructures. In order to investigate appropriate parameters for identifying efficient coupled wall geometries, an initial parametric study of over 2000 coupled wall geometries is reported. These analyses permitted the evaluation of the sensitivity of the structural response to various geometric parameters. The objective of this study is to investigate the elastic response parameters of coupled wall structures and to identify parameters that will permit an accurate initial estimate of the global behavior of a coupled system, the local behavior of the coupling beams and the interaction between the global and local behaviors. Using elastic analysis and gross section properties, the role of representative geometric parameters in the response of coupled structures is illustrated. The effect of using various code-prescribed reduced section properties is also discussed. The critical role of the coupling beam design is also illustrated.

Multifractality and Self-Adjustment of the Attraction Channel of Stock Market

For different evolutionary stages of the stock market, the fractal dimensionality of the attraction zone was estimated for the short-term and medium-term dynamic structures using by way of example the cost of the futures contract by the i>Standard and Poors 500 stock index. Adaptation of the stock market to a new environment was shown to be realized through reducing the fractal dimensionality, that is, chaoticity of motion, of the short-term dynamic structures. Minimization of the fractal dimensionality with the increase of the efficient existence of the dynamic component substructures was shown to be the prerequisite for stability of the multifractal dynamic system of the stock market.

Re-Refinement of Composite Modulated Nb2Zr x−2O2x+1 (x = 8) Using Synchrotron Radiation Data

The crystal structure of Nb2Zr_{x-2}O_{2x + 1}, x = 8, has been re-refined as a composite modulated structure using synchrotron radiation data measured at energies below the Zr K absorption edge. The structure comprises one-atom thick layers of two substructures stacked alternately along the b direction. The two component substructures are, in general, mutually incommensurable along their common a-axis directions and are referred to as the metal substructure (M), space group Amma, aM = 5.1348 (2), bM = 4.9590 (2), cM = 5.2908 (3) Å, and the oxygen substructure (O), space group Imam, aO = 2.4164, bO = bM = b, cO = cM = c, respectively. The four basis vectors used to index reciprocal space, based on the more strongly scattering metal substructure, are a^{\ast}_{M}, b*, c* and q M . The primary modulation wavevector q M = ^{\ast}_{M} − 2a^{\ast}_{M} + b* - 1/8 a^{\ast}_{M} + b* for x = 8. The overall superspace-group symmetry is Amma(\alpha10)0s0. Two sets of intensity data recorded at room temperature, 8 eV (\lambda_n = 0.6892 Å) and 1450 eV (\lambda_f = 0.7492 Å) below the Zr K absorption edge, were refined to an overall R(\lambda_n) = 0.0377 and R(\lambda_f) = 0.0439. The displacive modulation wave amplitudes obtained from these refinements agree well with those previously obtained for an x = 12 member. Difference Fourier maps show that metal-atom ordering is virtually negligible.

Engineering multiversion neural-net systems.

In this paper we address the problem of constructing reliable neural-net implementations, given the assumption that any particular implementation will not be totally correct. The approach taken in this paper is to organize the inevitable errors so as to minimize their impact in the context of a multiversion system, i.e., the system functionality is reproduced in multiple versions, which together will constitute the neural-net system. The unique characteristics of neural computing are exploited in order to engineer reliable systems in the form of diverse, multiversion systems that are used together with a "decision strategy" (such as majority vote). Theoretical notions of "methodological diversity" contributing to the improvement of system performance are implemented and tested. An important aspect of the engineering of an optimal system is to overproduce the components and then choose an optimal subset. Three general techniques for choosing final system components are implemented and evaluated. Several different approaches to the effective engineering of complex multiversion systems designs are realized and evaluated to determine overall reliability as well as reliability of the overall system in comparison to the lesser reliability of component substructures.