Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations

The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented.     

Prediction of performance and exhaust emissions of a diesel engine fueled with biodiesel produced from waste frying palm oil

Biodiesel is receiving increasing attention each passing day because of its fuel properties and compatibility with the petroleum-based diesel fuel (PBDF). Therefore, in this study, the prediction of the engine performance and exhaust emissions is carried out for five different neural networks to define how the inputs affect the outputs using the biodiesel blends produced from waste frying palm oil. PBDF, B100, and biodiesel blends with PBDF, which are 50% (B50), 20% (B20) and 5% (B5), were used to measure the engine performance and exhaust emissions for different engine speeds at full load conditions. Using the artificial neural network (ANN) model, the performance and exhaust emissions of a diesel engine have been predicted for biodiesel blends. According to the results, the fifth network is sufficient for all the outputs. In the fifth network, fuel properties, engine speed, and environmental conditions are taken as the input parameters, while the values of flow rates, maximum injection pressure, emissions, engine load, maximum cylinder gas pressure, and thermal efficiency are used as the output parameters. For all the networks, the learning algorithm called back-propagation was applied for a single hidden layer. Scaled conjugate gradient (SCG) and Levenberg–Marquardt (LM) have been used for the variants of the algorithm, and the formulations for outputs obtained from the weights are given in this study. The fifth network has produced R² values of 0.99, and the mean % errors are smaller than five except for some emissions. Higher mean errors are obtained for the emissions such as CO, NO_x and UHC. The complexity of the burning process and the measurement errors in the experimental study can cause higher mean errors.     

The effect of categorizing returned products in remanufacturing

An increasing number of companies have been implementing comprehensive recycling and remanufacturing programs. These endeavors typically involve the operation of joint manufacturing and remanufacturing systems. One of the major challenges in managing such hybrid systems is the stochastic nature of product returns. In particular, there is significant variability in the condition of the returns. This paper presents an approach for assessing the impact of quality-based categorization of returned products. Through extensive numerical studies on a continuous-time Markov chain model, we show that incorporation of returned product quality in the remanufacturing and disposal decisions can lead to significant cost savings. We find that these savings are amplified as the return quality decreases, and as the return rate increases. We also show that prioritizing higher quality returns in remanufacturing is, in general, a better strategy.     

Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions

Flaxseed protein concentrate containing-mucilage (FPCCM) was used to stabilize soybean oil-in-water emulsions. The effects of FPCCM concentration (0.5, 1.0, 1.5% w/v) and oil-phase volume fraction (5, 10, 20% v/v) on emulsion stability and rheological properties of the soybean oil-in-water emulsions were investigated. Z-average diameter, zeta-potential, creaming index and rheological properties of emulsions were determined. The result showed that FPCCM concentration significantly affected zeta-potential, creaming rate and emulsion viscosity. The increasing of FPCCM concentration led to a more negative charged droplet and a lower creaming rate. Oil-phase volume fraction significantly affected Z-average diameter, rheological properties, creaming index and creaming rate. With the increase of oil-phase volume fraction, both Z-average diameter and emulsion viscosity increased, while creaming index and creaming rate decreased. The rheological curve suggested that the emulsions were shear-thinning non-Newtonian fluids.     

Synthesis and properties of chitosan-modified poly(vinyl butyrate)

Modification of chitosan by grafting of vinyl butyrate was carried out in homogeneous phase using potassium persulfate as redox initator and 1.5% acetic acid as solvent. The percent grafting and grafting efficiency were analysed and the high grafting efficiency up to 94% was observed. The effects of reaction variables such as monomer concentration, initiator concentration, temperature and reaction time were investigated. It was observed that the solubility of chitosan was markedly reduced after grafting with vinyl butyrate. The grafted product is insoluble in common organic solvents as well in dilute organic and inorganic acids. Characterization of the graft copolymers were carried out by using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) technics. Characteristic signal of carbonyl group was observed at 1,731 cm⁻¹ which belongs to the poly vinyl butyrate segments in the graft copolymer. The melting transition of the chitosan main chain in the copolymer shifted to 124°C from its original value 101°C. In addition to these, we have also studied topology of the graft copolymer and the SEM micrograph showed continuous homogenous matrix which means there is no phase separation.     

Rheological analysis of ceramic pastes

This paper is concerned with a number of means of characterising the rheological properties of a ceramic paste. The intrinsic flow behaviour of the paste, during upsetting, is studied experimentally by using multi coloured paste samples, as well as by a finite element numerical computation. The flow behaviour of the paste is approximated by an elasto-viscoplastic material constitutive model and implemented by using an established finite element code. The material flow properties, which are necessary for the implementation of the numerical model, were obtained using the squeeze film and hardness indentation test configurations. The flow fields generated by the simulation are shown to be a good accord with the experimental observations. The experimental procedure for selecting the material parameters which are necessary for the implementation of the numerical model is described. The accuracy of the numerical method described is also evaluated by comparing the simulation results with experimental data obtained from the net upsetting force against the imposed relative displacement behaviour and the flow visualisation of deformed coloured layers. In these respects, a comparison of the finite element model predictions and the experimental results demonstrates a good mutual agreement.     

K-shell absorption jump factors and jump ratios in elements between Tm (Z = 69) and Os (Z = 76) derived from new mass attenuation coefficient measurements

The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm₂O₃, Yb₂O₃ compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56-77 keV, were done in a transmission geometry utilizing the K_α1, K_α2, K_β1 and K_β2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV γ-photons from an ⁵⁷Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.     

Load Rating and Reliability Analysis of an Aerial Guideway Structure for Condition Assessment

Aerial guideways are elegant transportation structures that are seen at airports, theme parks, and crowded urban areas. The guideways generally consist of continuous, prestressed concrete beam spans, precast concrete columns, and steel beam-column connections. Although there are guidelines prepared as a supplement to conventional highway and railway bridge design codes, aerial guideways form a different class, relatively less studied compared to common highway bridges. The primary objective of this paper is to present a study to better understand the structural behavior and capacity used in an existing guideway structural system which has been in service for about 35?years. The load demand on the guideway system has increased by about 50% over the years. The structural system is composed of six-span continuous prestressed concrete bridge segments. In order to develop models that bound the possible existing condition of the structure, several models are developed by changing the most critical parameters. The critical parameters are categorized as material properties, prestress losses, boundary conditions, and continuity conditions. Sensitivity studies are conducted using eight parametric models for simulations with moving loads for the two different train types. The load rating and reliability indexes are computed for all the cases under different loading conditions. The parameters that have the most influence on the load rating and reliability are also presented. The information generated from these analyses can be utilized for better-focused visual inspection and can also be used for developing a long-term structural monitoring plan.     

In vitro characterisation of probiotic properties of Enterococcus faecium and Enterococcus durans strains isolated from raw milk and traditional dairy products

In this study, some probiotic characteristics such as antimicrobial activity, vancomycin resistance, growth ability at pH, resistance to bile salts, bile salt deconjugation and hydrophobicity of 30 Enterococcus faecium and Enterococcus durans strains isolated and identified from raw milk and various dairy products were investigated. According to the study results, antimicrobial activity profiling, pH and bile salt resistance and bile salt deconjugation ability of Enterococcus strains varied depending on the species and strains and all the strains showed resistance to the tested bile salt concentrations. It was concluded that the E. faecium and E. durans strains tested showed probiotic characteristics and have the potential to be used in food production.     

Removal of heavy‐metal ions by magnetic beads containing triazole chelating groups

The aim of this study was to prepare magnetic beads that could be used for the removal of heavy‐metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [m‐poly(EGDMA–VTAZ)] beads were produced by suspension polymerization in the presence of a magnetite Fe₃O₄ nanopowder. The specific surface area of the m‐poly(EGDMA–VTAZ) beads was 74.8 m²/g with a diameter range of 150–200 μm, and the swelling ratio was 84%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA–VTAZ) beads was 14.8%. The maximum binding capacities of the m‐poly(EGDMA–VTAZ) beads from aquous solution were 284.3 mg/g for Hg²⁺, 193.8 mg/g for Pb²⁺, 151.5 mg/g for Cu²⁺, 128.1 mg/g for Cd²⁺, and 99.4 mg/g for Zn²⁺. The affinity order on a mass basis was Hg²⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺> Zn²⁺. The binding capacities from synthetic waste water were 178.1 mg/g for Hg²⁺, 132.4 mg/g for Pb²⁺, 83.5 mg/g for Cu²⁺, 54.1 mg/g for Cd²⁺, and 32.4 mg/g for Zn²⁺. The magnetic beads could be regenerated (up to ca. 97%) by a treatment with 0.1M HNO₃. These features make m‐poly(EGDMA–VTAZ) beads potential supports for heavy‐metal removal under a magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009