Structural health monitoring: a practical approach to achieving in-situ and site-specific warning of pipeline corrosion and coating failure

An approach to achieving the ambitious goal of cost effectively extending the safe operation life of energy pipelines to, for instance, 100 years is the application of structural health monitoring and life prediction tools that are able to provide long-term remnant pipeline life prediction and in-situ pipeline condition monitoring. A critical step in pipeline structural health monitoring is the enhancement of technological capabilities that are required for quantifying the effects of key factors influencing buried pipeline corrosion and environmentally assisted materials degradation, and the development of condition monitoring technologies that are able to provide in-situ monitoring and site-specific warning of pipeline damage. This paper provides an overview of our current research aimed at developing new sensors for monitoring, categorising and quantifying the level and nature of external pipeline and coating damages under the combined effects of various inter-related variables and processes such as localised corrosion, coating damage and disbondment, cathodic shielding. The concept of in-situ monitoring and site-specific warning of pipeline corrosion is illustrated by a case of monitoring localised corrosion under disbonded coatings using a new corrosion monitoring probe. A basic principle that underpins the use of sensors to monitor localised corrosion has been presented: Localised corrosion and coating failure are not an accidental occurrence, it occurs as the result of fundamental thermodynamic instability of a metal exposed to a specific environment. Therefore corrosion and coating disbondment occurring on a pipeline will also occur on a sensor made of the same material and exposed to the same pipeline condition. Although the exact location of localised corrosion or coating disbondment could be difficult to pinpoint along the length of a buried pipeline, the ‘worst-case scenario’ and high risk pipeline sections and sites are predictable. Sensors can be embedded at these strategic sites to collect data that contain ‘predictor features’ signifying the occurrence of localised corrosion, CP failure, coating disbondment and degradation. Information from these sensors will enable pipeline owners to prioritise site survey and inspection operations, and to develop maintenance strategy to manage aged pipelines, rather than replace them.

Improving on- and off-campus student performance in structural mechanics

This paper investigates the performance of 329 (173 on- and 186  off-campus) students enrolled in two structural mechanics units at Deakin University, a leader in engineering distance-education in Australia. The two units experience unacceptably high rates of failure. An analysis of the assignment, laboratory and examination marks is presented. Consideration is also given to the total marks. The results show that on-campus students perform better in structural mechanics than their off-campus counterparts. Plots of the student performance distributions for the three assessment methods are provided (for each unit) and high failure rates are linked to low examination marks. Students tend to perform best in assignments and worst in examinations. Parametric statistical tests show a correlation between the continuous assessment and examination marks. To motivate students to fully participate in continuous assessment tasks the authors therefore propose several changes to the assessment criteria and marking schemes.

Delivery and assessment strategies to improve on- and off-campus student performance in structural mechanics

This paper considers the delivery and assessment strategies used in two structural mechanics units at Deakin University, a leader in distance education in Australia. The two units have had unacceptably high rates of student failure. Student perceptions of the delivery method were analysed and an investigation was carried out of the performance of 329 (173 on- and 156 off-campus) students enrolled in the two units. An analysis of the assignment, laboratory and examination marks is presented. Consideration is also given to the total marks. The results show that on-campus students performed better in structural mechanics than their off-campus counterparts. Plots of the distributions of student performance for the three assessment methods are provided (for each unit) and high failure rates are linked to low examination marks. Students tended to perform best in assignments and worst in examinations. Parametric statistical tests show a correlation between the marks obtained in continuous assessment and in examinations, and it is therefore proposed that, in order to improve performance, the students must be encouraged to participate fully in all aspects of the course. Many students were unenthusiastic about laboratory practical sessions and did not think they aided their understanding of the theoretical material. Motivation to participate is often dependent on the perceived relevance of a given task and its contribution to the total mark and, thus, to help motivate students to participate fully in the continuous assessment tasks, the authors propose several changes to the delivery methods, as well as to assessment criteria and marking schemes.

Structural and functional properties of human multidrug resistance protein 1 (MRP1/ABCC1)

Multidrug ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1) play an important role in the extrusion of drugs from the cell and their overexpression can be a cause of failure of anticancer and antimicrobial chemotherapy. Recently, the mouse P-gp/Abcb1a structure has been determined and this has significantly enhanced our understanding of the structure-activity relationship (SAR) of mammalian ABC transporters. This paper highlights our current knowledge on the structural and functional properties and the SAR of human MRP1/ABCC1. Although the crystal structure of MRP1/ABCC1 has yet to be resolved, the current topological model of MRP1/ABCC1 contains two transmembrane domains (TMD1 and TMD2) each followed by a nucleotide binding domain (NBD) plus a third NH2-terminal TMD0. MRP1/ABCC1 is expressed in the liver, kidney, intestine, brain and other tissues. MRP1/ABCC1 transports a structurally diverse array of important endogenous substances (e.g. leukotrienes and estrogen conjugates) and xenobiotics and their metabolites, including various conjugates, anticancer drugs, heavy metals, organic anions and lipids. Cells that highly express MRP1/ABCC1 confer resistance to a variety of natural product anticancer drugs such as vinca alkaloids (e.g. vincristine), anthracyclines (e.g. etoposide) and epipodophyllotoxins (e.g. doxorubicin and mitoxantrone). MRP1/ABCC1 is associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. However, most compounds that efficiently reverse P-gp/ABCB1-mediated multidrug resistance have only low affinity for MRP1/ABCC1 and there are only a few effective and relatively specific MRP1/ABCC1 inhibitors available. A number of site-directed mutagenesis studies, biophysical and photolabeling studies, SAR and QSAR, molecular docking and homology modeling studies have documented the role of multiple residues in determining the substrate specificity and inhibitor selectivity of MRP1/ABCC1. Most of these residues are located in the TMs of TMD1 and TMD2, in particular TMs 4, 6, 7, 8, 10, 11, 14, 16, and 17, or in close proximity to the membrane/cytosol interface of MRP1/ABCC1. The exact transporting mechanism of MRP1/ABCC1 is unclear. MRP1/ABCC1 and other multidrug transporters are front-line mediators of drug resistance in cancers and represent important therapeutic targets in future chemotherapy. The crystal structure of human MRP1/ABCC1 is expected to be resolved in the near future and this will provide an insight into the SAR of MRP1/ABCC1 and allow for rational design of anticancer drugs and potent and selective MRP1/ABCC1 inhibitors.

Potential applications of discrete-event simulation and fuzzy rule-based systems to structural reliability and availability

This chapter discusses and illustrates some potential applications of discrete-event simulation (DES) techniques in structural reliability and availability analysis, emphasizing the convenience of using probabilistic approaches in modern building and civil engineering practices. After reviewing existing literature on the topic, some advantages of probabilistic techniques over analytical ones are highlighted. Then, we introduce a general framework for performing structural reliability and availability analysis through DES. Our methodology proposes the use of statistical distributions and techniques – such as survival analysis – to model component-level reliability. Then, using failure- and repair-time distributions and information about the structural logical topology (which allows determination of the structural state from their components’ state), structural reliability, and availability information can be inferred. Two numerical examples illustrate some potential applications of the proposed methodology to achieving more reliable and structural designs. Finally, an alternative approach to model uncertainty at component level is also introduced as ongoing work. This new approach is based on the use of fuzzy rule-based systems and it allows the introduction of experts’ opinions and evaluations in our methodology.

Structural composites embedded with lithium polymer batteries

Structural battery composites that concurrently carry load and store electric energy will
transform future vehicles. They can replace inert structural components and simultaneously provide supplementary power for light load applications. Rechargeable lithium polymer battery cells are embedded into carbon fibre/epoxy matrix composite laminates, which are then tested under tension and three-point bending to investigate the mechanical and electrical performances of structural batteries. The experimental results show that the integration of battery cells into composite laminates has negligible impact on the mechanical strengths of the composite structures. Furthermore, the battery cells remain 95% effective at loads up to about 60% of the ultimate flexural failure load and 50% of the ultimate tensile failure load.

Farmland prices, structural breaks and panel data

Previous time series evidence has indicated that farmland prices and cash rents are not cointegrated, a finding at odds with the present value model of farmland prices. We argue that this failure to find cointegration may be due to low power of tests and to the presence of structural change representing a shifting risk premium on farmland investments. To accommodate this possibility, we use panel unit root and cointegration methods that are more powerful than conventional time series methods and allow for breaks in the cointegration relationship. Our results, based on a large panel covering 31 US states between 1960 and 2000, suggest that the present value model of farmland prices cannot be rejected. © Oxford University Press and Foundation for the European Review of Agricultural Economics 2007; all rights reserved.

Structural transformation of polyacrylonitrile fibers during stabilization and low temperature carbonization

The effect of oxidative stabilization and carbonization processes on the structure, mass and mechanical properties of polyacrylonitrile (PAN) precursor fibers was analyzed. A gradual densification of the fibers occurring from mass loss, decrease in fiber diameter and increase in density were observed after stabilization at a maximum temperature of 255 °C and carbonization at a maximum temperature of 800 °C. The tensile strength and modulus of the fibers were found to decrease after stabilization but then increased after low temperature carbonization. The thermal processing of the precursor fibers affected their mode of failure after tensile loading, changing from a ductile type of failure to a brittle type. The type of failure correlated well with the crystal structure changes in the fibers. Whilst the PAN precursor fiber started to exotherm above 225 °C in air, no prominent exothermic reaction was measured in the carbonized fibers in air up to 430 °C. The aromatization index of stabilized fiber was calculated to be ∼66%, and that of carbonized fiber was ∼99%. FTIR studies indicated that the variation in the chemical structure of the fibers with the stabilization of the fibers. Radial heterogeneity in the stabilized fibers was observed however it was not promoted to the carbonized fibers. Finally, a method to calculate mass retention of PAN precursor fiber after heat treatment was developed, and the calculated percentage mass retained of the precursor fiber after oxidation and carbonization were found to be 81% and 51%, respectively. . This study proposes an effective method to calculate the percentage of mass retained by precursor fibers after stabilization and low temperature carbonization to provide a model for evaluating carbon fiber yield from a given amount of fibers.