Numerical Substructure Research Articles

Improved control algorithm for real‐time substructure testing

AbstractReal‐time substructure testing is a novel method of testing structures under dynamic loading. The complete structure is separated into two substructures, one of which is tested physically at large scale and in real time, so that time‐dependent non‐linear behaviour of the substructure is realistically represented. The second substructure represents the surrounding structure, which is modelled numerically. In the current formulation this numerical substructure is assumed to remain linear. The two substructures interact in real‐time so that the response of the complete structure, incorporating the non‐linear behaviour of the physical substructure, is accurately represented. This paper presents several improvements to the linear numerical modelling of substructures for use in explicit time‐stepping routines for real‐time substructure testing. An extrapolation of a first‐order‐hold discretization is used which increases the accuracy of the numerical model over more direct explicit methods. Additionally, an integral form of the equation of motion is used in order to reduce the effects of noise and to take into account variations of the input over a time‐step. In order to take advantage of this integral form, interpolation of the model output is performed in order to smooth the output. The improvements are demonstrated using a series of substructure tests on a simple portal frame. While the testing approach is suitable for cases in which the physical substructure behaves non‐linearly, the results presented here are for fully linear systems. This enables comparisons to be made with analytical solutions, as well as with the results of tests based on the central difference method. Copyright © 2001 John Wiley & Sons, Ltd.

A Comparison of Two Sub-structuring Techniques for Representing the Modal Properties of Tires

Abstract Different numerical sub-structuring techniques for the representation of tire modal behavior have been developed in the past 20 years. By using these numerical techniques reduced dynamic models are obtained which can not only be used for internal studies but also be provided to the automobile industry and linked to reduced dynamic vehicle models in order to optimize the coupled vehicle-tire response for noise vibration and harshness purposes. Two techniques that have been developed in a custom-made finite element code are presented: 1) the component mode synthesis type models for which the wheel center interface is free and 2) the Craig and Bampton type models for which the wheel center interface is fixed. For both techniques the interface between the tire and the ground is fixed. The choice of fixed or free wheel center boundary condition is arbitrary. In this paper we will compare the formulation of these two numerical methods, and we will show the equivalency of both methods by showing the results obtained in terms of frequency and transfer functions. We will show that the two methods are equivalent in principle and the reduced dynamic models can be converted from one to the other. The advantages-disadvantages of each method will be discussed along with a comparison with experimentally obtained results.

Chapter 13 Mapping Proteins to Nuclear Pore Complexes by Immunogold Electron Microscopy

The nuclear pore complex (NPC), controlling the exchange of matter and information between cell nucleus and cytoplasm, is an amazing structure having a total mass of approximately 125 MDa, measuring approximately 120 nm in diameter and 70 nm in length and being composed of presumably more than 100 different polypeptides, many occurring in multiple copies. Up to now, only about 10% of the estimated more than 100 different proteins of the metazoan NPC have been identified, characterized, and mapped to the NPC. However, further nucleoporins are being identified at a high rate. To understand their tasks within the NPC, it is crucial to find out about their location within the NPC and their association with the numerous substructures of the NPC, such as cytoplasmic and karyoplasmic rings, spokes, central granules, and cytoplasmic and karyoplasmic filaments. A frequently used and successful method for localizing nucleoporins to the NPC is immunogold electron microscopy. The principle of the method is to raise antibodies against specific nucleoporins; to react permeabilized cells, isolated nuclei, or histological sections with these primary antibodies; and to visualize the subcellular binding sites of the antibodies by electron microscopy.

Internal micromorphology of the frons plate in females of the oriental hornet.

Scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDS) have been used to study the internal micromorphology of the frons plate in the Oriental hornet, Vespa orientalis. A conical shaped organ was described which is recessed into the frons plate and projects toward the interior of the acoustic box. The latter is located on the inner side of the frons plate. On the exterior of the conical region are observed aggregates containing Ca and Si, and a thin transparent membrane bearing a hole in its center. The innermost surface of the conical structure terminates bluntly as a convex lentiform tip, bearing a transparent oval-shaped window in its center. The conical organ, excepting the window, is enclosed in several layers of epithelium. The structure of this many-layered conical organ is highly complex; its numerous sub-structures and the possible role as a gravity sense organ are discussed. © 1993 Wiley-Liss, Inc.

Numerical solution technique for transient, two-dimensional combustion with multi-step kinetics

For numerical combustion problems, computational time and storage requirements scale approximately with the square of the number of chemical species. Therefore, the most difficult cases that can be solved using elementary chemical kinetics have been one-dimensional transient and two-dimensional steady formulations. This limitation and the established shortcomings of global reactions have encouraged recent development of simplified but accurate multi-step kinetics schemes. The present investigation uses one of these simplified reaction mechanisms to determine if solution of a multi-dimensional, transient, reacting flow problem is possible without resort to overly simplified, global kinetics. A laminar, two-dimensional, transient, viscous flow model has been developed which incorporates a chemical kinetics mechanism for propane consisting of four reversible reactions and only seven species. The model is used to investigate the initiation and propagation of a flame subjected to heat transfer, wall motion and shear flow. The mathematical model simulates the physical and chemical processes occurring near the centerline of a thin-gap formed by two cold, solid surfaces as one surface moves first toward and then away from the other. The governing conservation equations for mass, momentum, energy and chemical species are simplified using the thin-gap approximation. The problem is transformed to eliminate the continuity equation by using a compressible stream function formulation. The resulting mixed order system of nonlinear, boundary value problems is solved by a semi-discrete numerical procedure which employs a finite element collocation method and adaptive grid technique. Both non-reacting and reacting cases are solved to demonstrate the effect of the shear flow and cold surfaces on the flow field and on the developing laminar flame. The results reveal a complex flow with numerous substructures caused by the interaction of the developing flame with cold fluid trapped in the boundary layer adjacent to the stationary wall. The reacting flow results represent the first calculation of a laminar, reacting flow in a moving wall geometry using nonequilibrium, multi-step chemistry while simultaneously resolving the momentum and thermal boundary layers.

A Tree System Approach for Fingerprint Pattern Recognition

The purpose of this paper is to demonstrate how a syntactic approach and, in particular, a tree system may be used to represent and classify fingerprint patterns. The fingerprint impressions are subdivided into sampling squares which are preprocessed and postprocessed for feature extraction. A set of regular tree languages is used to describe the fingerprint patterns and a set of tree automata is used to recognize the coded patterns. In order to infer the structural configuration of the encoded fingerprints, a grammatical inference system is developed. This sytem utilizes a simple procedure to infer the numerous substructures and relies on a reachability matrix and a man-machine interactive technique for the inference of complex structures. The 92 fingerprint impressions were used to test the proposed approach. A set of 193 tree grammars was inferred from each sampling square of the 4 × 4 sampling matrix which is capable of generating about 2 × 1034 classes for the fingerprint patterns.

A Tree System Approach for Fingerprint Pattern Recognition

The purpose of this paper is to demonstrate how a syntactic approach and, in particular, a tree system may be used to represent and classify fingerprint patterns. The fingerprint impressions are subdivided into sampling squares which are preprocessed and postprocessed for feature extraction. A set of regular tree languages is used to describe the fingerprint patterns and a set of tree automata is used to recognize the coded patterns. In order to infer the structural configuration of the encoded fingerprints, a grammatical inference system is developed. This system utilizes a simple procedure to infer the numerous substructures and relies on a reachability matrix and a man-machine interactive technique for the inference of complex structures. The 92 fingerprint impressions were used to test the proposed approach. A set of 193 tree grammars was inferred from each sampling square of the 4 × 4 sampling matrix which is capable of generating about 2 × 1034 classes for the fingerprint patterns.