Full-Scale Marine Exposure Tests on Treated and Untreated Concretes Initial 7-Year Results

An extensive chloride profiling program was undertaken on concrete pier stems erected in the vicinity of the Dornoch Bridge located at the Dornoch Firth in Northeast Scotland. The pier stems were 2 m (6.562 ft) high and octagonal in plan with 0.66 m (2.165 ft) wide faces. The piers were constructed in sets of three with the lowest of each set in the tidal zone and the highest in the atmospheric zone. The pier stems were placed in such a way that they would represent the exposure conditions of the actual bridge piers of the Dornoch Bridge. In all, six of the pier stems were made using plain ordinary portland cement (OPC) concrete (with three of these having the surface treated with silane); the remaining three pier stems had a concrete containing caltite as an additive. Three exposurezones were studied: the tidal zone, the splash zone, and the atmospheric zone. The tidal zone was further subdivided into two levels defined as low-level and high-level. Chloride profiles were obtained from the different regimes over a period of 7 years for all nine pier stems. This paper describes the nature of chloride ingress and the usefulness of diffusion parameters in classifying each exposure regimes. Furthermore, the effectiveness of silane and caltite in protecting concrete from chloride ingress in different exposure zones was studied.

A Virtual Inspection Technique for Assessing the Dimensional Accuracy of Forged Compressor Blades Using FE Modeling and CMM Inspection

This paper presents research for developing a virtual inspection system that evaluates the dimensional tolerance of forged aerofoil blades formed using the finite element (FE) method. Conventional algorithms adopted by modern coordinate measurement processes have been incorporated with the latest free-form surface evaluation techniques to provide a robust framework for the dimensional inspection of FE aerofoil models. The accuracy of the approach had been verified with a strong correlation obtained between the virtual inspection data and coordinate measurement data from corresponding aerofoil components.

Novel loading tests on full-scale tapered member portal frames

This paper presents the experimental results of loading tests on two 18m span tapered member portal frames designed to BS 5950. Deflection test results for vertical, lateral and combined loading cases are compared with the predictions given by elastic analysis to BS 5950 and shown to be favourable. The predicted ultimate capacities and modes of failure, which were by lateral-torsional buckling of the columns, were also found to agree with the experimental behaviour. It was found that the method of modelling the tapered members as a series of prismatic elements gave good comparison with test results.

Validity and reliability of cardiorespiratory measurements recorded by the LifeShirt during exercise tests

The LifeShirt is a novel ambulatory monitoring system that records cardio respiratory measurements outside the laboratory. Validity and reliability of cardiorespiratory measurements recorded by the LifeShirt were assessed and two methods of calibrating the LifeShirt were compared. Participants performed an incremental treadmill test and a constant work rate test (65% peak oxygen uptake) on four occasions (>48 In apart) and wore the LifeShirt, COSMED system and Polar Sport Tester simultaneously. The LifeShirt was calibrated using two methods: comparison to a spirometer; and 800 ml fixed-volume bag. Ventilation, respiratory rate, expiratory time and heart rate recorded by the LifeShirt were compared to measurements recorded by laboratory equipment. Sixteen adults participated (6M: 10F); mean (SD) age 23.1 (2.9) years. Agreement between the LifeShirt and laboratory equipment was acceptable. Agreement for ventilation was improved by calibrating the LifeShirt using a spirometer. Reliability was similar for the LifeShirt and the laboratory equipment. This study suggests that the LifeShirt provides a valid and reliable method of ambulatory monitoring. (C) 2009 Elsevier B.V. All rights reserved.

Apolipoprotein epsilon4 and neuropsychological performance in Alzheimer's disease and vascular dementia

The apolipoprotein (APOE) epsilon4 allele is a genetic risk factor for the development of Alzheimer's disease (AD). It has also been associated with vascular dementia (VaD) in some but not all studies. Previous studies have examined the role of APOE in predicting performance on cognitive tests in both demented and non-demented populations. In cognitively intact individuals, statistically significant group differences between APOE epsilon4 carriers and non-carriers have been demonstrated for several cognitive domains. In AD studies of the impact of APOE epsilon4 on cognition have been conflicting while no previous study has assessed cognition and impact of APOE epsilon4 in VaD. In this study we investigated the impact of APOE epsilon4 on performance in neuropsychological tests including information processing speed in patients with mild-moderate AD and VaD. We incorporated both computerized and pen and paper tests to ensure a sensitive method of assessing cognition. 109 patients participated in the study (VaD=41, AD=68). Neurocognitive performance of 44 epsilon4 present AD patients was compared to 24 epsilon4absent patients and performance of 23 epsilon4 present VaD patients was compared to 18 epsilon4 absent patients. There was evidence that APOE epsilon4 conferred a risk of poorer cognitive functioning in both patient groups. In the AD group presence of epsilon4 conferred a negative impact on some measures of speed of information processing and immediate recall while in the VaD group epsilon4 present patients had evidence of poorer accuracy on tasks such as choice reaction time and spatial working memory. In AD and VaD groups epsilon4 present patients showed impairment in selective attention. These findings provide further support of the negative impact of the epsilon4 allele in cognition.

Predictive Current Control of Doubly Fed Induction Generators

This paper presents a predictive current control strategy for doubly-fed induction generators (DFIG). The method predicts the DFIG’s rotor current variations in the synchronous reference frame fixed to the stator flux within a fixed sampling period. This is then used to directly calculate the required rotor voltage to eliminate the current errors at the end of the following sampling period. Space vector modulation is used to generate the required switching pulses within the fixed sampling period. The impact of sampling delay on the accuracy of the sampled rotor current is analyzed and detailed compensation methods are proposed to improve the current control accuracy and system stability. Experimental results for a 1.5 kW DFIG system illustrate the effectiveness and robustness of the proposed control strategy during rotor current steps and rotating speed variation. Tests during negative sequence current injection further demonstrate the excellent dynamic performance of the proposed PCC method.

Viscoelastic Material Models of Polypropylene for Thermoforming Applications

Polypropylene (PP), a semi-crystalline material, is typically solid phase thermoformed at temperatures associated with crystalline melting, generally in the 150° to 160°Celsius range. In this very narrow thermoforming window the mechanical properties of the material rapidly decline with increasing temperature and these large changes in properties make Polypropylene one of the more difficult materials to process by thermoforming. Measurement of the deformation behaviour of a material under processing conditions is particularly important for accurate numerical modelling of thermoforming processes. This paper presents the findings of a study into the physical behaviour of industrial thermoforming grades of Polypropylene. Practical tests were performed using custom built materials testing machines and thermoforming equipment at Queen′s University Belfast. Numerical simulations of these processes were constructed to replicate thermoforming conditions using industry standard Finite Element Analysis software, namely ABAQUS and custom built user material model subroutines. Several variant constitutive models were used to represent the behaviour of the Polypropylene materials during processing. This included a range of phenomenological, rheological and blended constitutive models. The paper discusses approaches to modelling industrial plug-assisted thermoforming operations using Finite Element Analysis techniques and the range of material models constructed and investigated. It directly compares practical results to numerical predictions. The paper culminates discussing the learning points from using Finite Element Methods to simulate the plug-assisted thermoforming of Polypropylene, which presents complex contact, thermal, friction and material modelling challenges. The paper makes recommendations as to the relative importance of these inputs in general terms with regard to correlating to experimentally gathered data. The paper also presents recommendations as to the approaches to be taken to secure simulation predictions of improved accuracy.

Efficient Evaluation of Multidimensional Time-Varying Density Forecasts

We propose two simple evaluation methods for time varying density forecasts of continuous higher dimensional random variables. Both methods are based on the probability integral transformation for unidimensional forecasts. The first method tests multinormal densities and relies on the rotation of the coordinate system. The advantage of the second method is not only its applicability to any continuous distribution but also the evaluation of the forecast accuracy in specific regions of its domain as defined by the user’s interest. We show that the latter property is particularly useful for evaluating a multidimensional generalization of the Value at Risk. In simulations and in an empirical study, we examine the performance of both tests.

Panel unit root tests in the presence of cross-sectional dependence: finite sample performance and an application

This paper examines the finite sample properties of three testing regimes for the null hypothesis of a panel unit root against stationary alternatives in the presence of cross-sectional correlation. The regimes of Bai and Ng (2004), Moon and Perron (2004) and Pesaran (2007) are assessed in the presence of multiple factors and also other non-standard situations. The behaviour of some information criteria used to determine the number of factors in a panel is examined and new information criteria with improved properties in small-N panels proposed. An application to the efficient markets hypothesis is also provided. The null hypothesis of a panel random walk is not rejected by any of the tests, supporting the efficient markets hypothesis in the financial services sector of the Australian Stock Exchange.