The effect of prior flexural prestrain on the stability of structural steel columns

Prior large bending deformations may cause a significant reduction in the buckling stress of a mild steel strut subjected to direct compression. Although the work arose in investigating the properties of mangled bars, that is bars which have been deliberately deformed so as to reduce initial geometric imperfections, the conclusions are equally applicable to other instances of plastic strain reversal, such as those which might arise due to earthquake or shock waves. Particular attention is drawn to the possibly potentially dangerous situation which may arise when a severely deformed element is straightened and then subjected to loading conditions which would be regarded as safe for a previously undeformed element. Buckling stresses have been computed from material data for the prestrained specimens and these values are compared with actual test results.     

An adsorption-based mercury sensor with continuous readout

A novel readout procedure for a mercury sensor has been proposed. The sensor is based on the surface adsorption. Mercury vapor is adsorbed at the surface of a thin gold layer patterned into four meanders which are connected into a Wheatstone bridge configuration. Sensing is achieved by the resistivity change of the gold film during mercury adsorption. Direct output from the sensor is electric voltage. It takes an additional procedure to convert voltage to mercury concentration. This type of sensor is improved by introducing continuous readout procedure for the voltage–concentration conversion. By using this readout procedure it is possible to monitor mercury vapor concentration as a function of time. Readout is based on the Langmuir time–dependent adsorption theory. This paper illustrates a practical implementation of the new readout procedure.     

Finding best algorithmic components for clustering microarray data

The analysis of microarray data is fundamental to microbiology. Although clustering has long been realized as central to the discovery of gene functions and disease diagnostic, researchers have found the construction of good algorithms a surprisingly difficult task. In this paper, we address this problem by using a component-based approach for clustering algorithm design, for class retrieval from microarray data. The idea is to break up existing algorithms into independent building blocks for typical sub-problems, which are in turn reassembled in new ways to generate yet unexplored methods. As a test, 432 algorithms were generated and evaluated on published microarray data sets. We found their top performers to be better than the original, component-providing ancestors and also competitive with a set of new algorithms recently proposed. Finally, we identified components that showed consistently good performance for clustering microarray data and that should be considered in further development of clustering algorithms.     

Assimilating synthetic GOES-R radiances in cloudy conditions using an ensemble-based method

The weather research and forecasting (WRF) model and the maximum likelihood ensemble filter (MLEF) data assimilation approach are used to examine the potential impact of observations from the future Geostationary Operational Environmental Satellite, generation R (GOES-R) on improving our knowledge about clouds. Synthetic radiances are assimilated from the 10.35 μm channel of the GOES-R advanced baseline imager (ABI) employing a ‘non-identical twins’ experimental setup. The experimental results are examined for an extratropical cyclone named Kyrill that produced unusually strong winds, widespread damage and fatalities in Western Europe in January 2007. The data assimilation problem is especially challenging for this case, as there is a large error in the model-simulated radiances resulting from incorrect cloud location. Although this problem is difficult to eliminate, data assimilation results indicate the potential of GOES-R data to significantly reduce these errors.     

Natural response of non-rigidly connected rectangular plates

The effect of a finite rotational restraint along two opposite edges of a rectangular plate is investigated for a range of mode numbers, aspect ratios and joint stiffnesses. Some practical applications are discussed by reference to welded joints. The extension of the theory to plate assemblies is briefly discussed.     

A case-based reasoning model that uses preference theory functions for credit scoring

We propose a case-based reasoning (CBR) model that uses preference theory functions for similarity measurements between cases. As it is hard to select the right preference function for every feature and set the appropriate parameters, a genetic algorithm is used for choosing the right preference functions, or more precisely, for setting the parameters of each preference function, as to set attribute weights. The proposed model is compared to the well-known k-nearest neighbour (k-NN) model based on the Euclidean distance measure. It has been evaluated on three different benchmark datasets, while its accuracy has been measured with 10-fold cross-validation test. The experimental results show that the proposed approach can, in some cases, outperform the traditional k-NN classifier.     

Beams on quasi-Winkler foundations

When an elastic foundation is incapable of exerting tensile reactions on the beam it supports, the Winkler model cannot be used throughout the whole span of the girder. The resulting problem leads to a set of nonlinear equations, and its complexity is further increased due to the necessity of visualizing the deflected shape a priori if the computing effort is to be minimized. An analysis of some simple case studies provides an estimate of the discrepancy between the Winkler model and its more realistic counterpart and concentrates on the type of problem where this discrepancy might be considerable.     

On edge-disturbance interaction and decoupling errors in thin-walled nonshallow spherical-shell frusta

This paper presents closed-form, compact and easily programmable formulae for the complete determination of internal actions and deformations stemming from arbitrary flexural and shearing actions uniformly distributed along the edges of a nonshallow thin-walled spherical-shell frustum. The shell edges are assumed to be sufficiently close to each other for bending-disturbance interaction to occur between them. The ensuing influence-coefficient expressions bring out the interaction component more explicitly than existing formulae. Unlike previous work on problems of spherical-shell frusta, the present study quantifies decoupling errors as continuous functions of a single fundamental parameter β. Edge-effect decoupling criteria are established for various error tolerances.     

Finite‐element model sensitivity in the vibration of partially embedded beams

Beams partially embedded in a Winkler foundation can exhibit the phenomenon of modal clustering. In this paper, a conventional finite‐element package is used in the comparison of the natural frequencies of such beams as calculated using a discretized finite‐element model and as computed from a closed‐form exact solution. The sensitivity of finite‐element models of varying degrees of refinement in predicting the incidence of modal clustering is discussed. It is shown that, in crude models, the clustering of modes is predicted accurately but other modes, even the lowest ones, can be unacceptably distorted. In very crude models, the finite‐element analysis may fail altogether in identifying the modal‐clustering phenomenon. Copyright © 1999 John Wiley & Sons, Ltd.     

Structural behaviour of closely packed inverted egg-shaped sewer linings during installation and under various restraint conditions

The paper describes the results of a numerical parametric study aimed at studying the structural response of closely packed inverted egg-shaped sewer linings. The effect of various restraint conditions which simulate different temporary support systems that may be used by the contractors during the installation of the lining, and of different loading configurations which may arise at different stages of grouting the annulus gap between the lining and the sewer, have been thoroughly investigated. Covering the feasible range of geometric, material and loading parameters, comprehensive design curves, based on the allowable stress- and deflection-limit criteria, are presented. A comparison between the various types of restraints leads to enhancement factors for the permissible grouting pressure or, alternatively, to reduction factors in terms of the lining thickness that could be used in designing lining systems. Finally, the structural response of inverted egg-shaped sewer linings is compared with their egg-shaped counterparts.