Damage Identification on the Tilff Bridge by Vibration Monitoring Using Optical Fiber Strain Sensors

Vibration testing is a well-known practice for damage identification of civil engineering structures. The real modal parameters of a structure can be determined from the data obtained by tests using system identification methods. By comparing these measured modal parameters with the modal parameters of a numerical model of the same structure in undamaged condition, damage detection, localization, and quantification is possible. This paper presents a real-life application of this technique to assess the structural health of the 50-year old bridge of Tilff, a prestressed three-cell box-girder concrete bridge with variable height. A complete ambient vibration survey comprising both vertical accelerations and axial strains has been carried out. The in situ use of optical fiber strain sensors for the direct measurement of modal strains is an original contribution of this work. It is a big step forward in the exploration of modal curvatures for damage identification because the accuracy in calculating the modal curvatures is substantially improved by directly measuring modal strains rather than deriving the modal curvatures from acceleration measurements. From the ambient vibrations, natural frequencies, damping factors, modal displacements and modal curvatures are extracted by the stochastic subspace identification method. These modal parameters are used for damage identification which is performed by the updating of a finite element model of the intact structure. The obtained results are then compared to the inspections performed on the bridge.     

A filter design method for minimizing ringing in a region of interest in MR spectroscopic images

Magnetic resonance spectroscopic imaging (MRSI) requires a relatively long time to sample k-space (the spatial frequency domain), effectively lowpass filtering the resulting reconstructed image. Ringing is especially problematic when a region of interest (ROI) is close to a bright region outside the ROI, since the bright region tends to create a ringing artifact into the ROI due to the lowpass nature of the data. In this paper, we propose a method that reduces the effect of a stronger signal region on a weaker signal in a nearby ROI by designing a postprocessing filter that steers the strong interference away from the ROI. The proposed method is computationally simple both in the design stage and in applying it to images. We present experiments that illustrate the value of the technique.     

Scan blindness phenomenon in conformal finite phased arrays of printed dipoles

Scan blindness phenomenon for finite phased arrays of printed dipoles on material coated, electrically large circular cylinders is investigated. Effects on the scan blindness mechanism of several array and supporting structure parameters, including curvature effects, are observed and discussed. A full-wave solution, based on a hybrid method of moments/Green's function technique in the spatial domain, is used to achieve the aforementioned goals. Numerical results show that the curvature affects the surface waves and hence the mutual coupling between array elements. As a result, the array current distribution of arrays mounted on coated cylinders are considerably different compared to similar arrays on planar platforms. Therefore, finite phased arrays of printed dipoles on coated cylinders show different behavior in terms of scan blindness phenomenon compared to their planar counterparts. Furthermore, this phenomenon is completely different for axially and circumferentially oriented printed dipoles on coated cylinders suggesting that particular element types might be important for cylindrical arrays.     

A Simple and Green Route for Room‐Temperature Synthesis of Gold Nanoparticles and Selective Colorimetric Detection of Cysteine

Gold nanoparticles (AuNPs) were synthesized at room temperature following a simple, rapid, and green route using fresh‐squeezed apple juice as a reducing reagent. The optimal AuNPs, based on the particle color, stability, and color change suitable for colorimetric detection of cysteine (Cys), are synthesized using 5 mL of 10% apple juice, 1 mL of 10 mM gold precursor solution, and 1 mL of 0.1 M NaOH. Under this set of parameters, the AuNPs are synthesized within 30 min at room temperature. The average size (11.1 ± 3.2 nm) and ζ potential (–36.5 mV) of the AuNPs synthesized were similar to those of AuNPs prepared via the conventional citrate‐reduction method. In the presence of Cys, unlike with any other amino acid, the AuNPs aggregated, possibly due to the gold–sulfur covalent interaction, yielding red‐to‐purple color change of the sample solution. The red‐shift of the localized surface plasmon resonance peak of the AuNPs responsible for the color change was recorded by UV‐vis spectrometer. The effect of other potential interferents such as glucose, ascorbic acid, K⁺, Na⁺, Ca²⁺, Zn²⁺, Ag⁺, Ni²⁺, Cu²⁺, Co²⁺, and Hg²⁺ were also examined. The results show that AuNPs can be used to selectively detect and measure Cys with a linear dependency in the range of 2 to 100 μM and a limit of detection (signal‐to‐noise ratio > 3) of 50 nM. The results suggest that the green‐synthesized AuNPs are useful for simple, rapid, and sensitive colorimetric detection of Cys, which is an essential amino acid in food and biological systems.     

Optimization of particle number,substrate concentration and temperature of batch immobilized reactor system for biohydrogen production by dark fermentation

Immobilized cell bioreactor was operated in batch mode for biohydrogen generation by dark fermentation from acid hydrolyzed waste wheat powder. It was aimed to optimize the fermentation conditions with the purpose of obtaining the highest hydrogen yield (Y_H2) and production rate (HPR) by applying Box–Wilson statistical experimental design method. Particle number (PN = 120–240; X₁), initial total sugar concentration (TS₀ = 10–30 g/l; X₂) and fermentation temperature (T = 35–55 °C; X₃) were selected as independent variables. Polyester fibers with particle diameter “Dp” = 0.5 cm were used as support material to immobilize microorganisms with heat-pretreated sludge. Quadratic equations for production yield and rate were developed by using experimental results. The maximum Y_H2 (3.21 mol H₂/mol glucose) and HPR (73.3 ml H₂/h) were predicted at the optimum conditions of PN = 240, TS₀ = 10 g/l and T = 44.9 °C. Also, analysis of variance, as well as sum of ranking difference test results demonstrated that fitting models were statistically significant.     

Modelling of sintering during rotational moulding of the thermoplastic polymers

This paper concerns the study of sintering phenomenon during rotational molding of polypropylene(PP),Polyvinylidenefluoride (PVDF) and Polymethyl methacrylate (PMMA). First, the coalescence (first step of sintering) of two grains has been followed. Bellehumeur’s model has been tested as a model to explain this phenomenon. In order to study the effect of neighboring grains on coalescence of two grains, a third grain has been put in contact with these two grains. For modeling the phenomenon in this case, Bellehumeur’s model has been modified by a geometric parameter called Farz Factor (FF), being this model validated by experimental test. Concerning densification, two different stages have been observed. In the first stage, before welding of the grains and formation of interphases between them, the grains are not stuck yet. The air trapped between the grains escapes through free ways between grains. This first step of densification is directly related to the coalescence where the density of the polymer varies very quickly. A new tridimensional model, based on a Body Centered Tetragonal (BCT) configuration, has been proposed to explain the densification during this first stage. In the second stage, the migration of air is controlled by diffusion.     

Hydrogen supply chain architecture for bottom-up energy systems models. Part 2: Techno-economic inputs for hydrogen production pathways

This article is the second paper of a serial study on hydrogen energy system modelling. In the first study, we proposed a stylized hydrogen supply chain architecture and its pathways for the representation of hydrogen systems in bottom-up energy system models. In this current paper, we aim to present and assess techno-economic inputs and bandwidths for a hydrogen production module in bottom-up energy system models. After briefly summarizing the current technological status for each production method, we introduce the parameters and associated input data that are required for the representation of hydrogen production technologies in energy system modelling activities. This input data is described both as numeric values and trend line modes that can be employed in large or small energy system models. Hydrogen production technologies should be complemented with hydrogen storage and delivery pathways to fully understand the system integration. In this context, we will propose techno-economic inputs and technological background information for hydrogen delivery pathways in later work, as the final paper of this serial study.     

Species distribution,molecular characteristics and vancomycin resistance gene profiles of Enterococcus sp. isolates from farmhouse cheeses in western Turkey

Species distribution, virulence traits and vancomycin resistance gene profiles of Enterococcus isolated from 43 home‐made artisan cheese samples collected from open markets, located in Aydin region of Turkey, were investigated. Of the 129 isolates, 95 were identified as Enterococcus sp.; Enterococcus faecium being the most prevalent species (82.1%), followed by Enterococcus faecalis (13.6%) and Enterococcus durans (1.0%). None of the enterococci were harbouring vanA or vanC, while seven isolates (7.3%) were shown to harbour vanB gene by multiplex PCR. gelE (49.4%) being the most prevalent virulence factor was followed by asa1 (27.3%), esp (22.1%), cylA (4.2%) and hyl (3.1%).