Residual Magnetic Field Testing System with Tunneling Magneto-Resistive Arrays for Crack Inspection in Ferromagnetic Pipes.

Ferromagnetic pipes are widely used in the oil and gas industry. They are subject to cracks due to corrosion, pressure, and fatigue. It is significant to detect cracks for the safety of pipes. A residual magnetic field testing (RMFT) system is developed for crack detection in ferromagnetic pipes. Based on this background, a detection probe based on an array of tunneling magneto-resistive (TMR) sensors and permanent magnets is exploited. The probe is able to partially magnetize the pipe wall and collect magnetic signals simultaneously. First, a theoretical analysis of RMFT is presented. The physics principle of RMFT is introduced, and a finite element model is built. In the finite element simulations, the effects of the crack length and depth on the RMFT signal are analyzed, and the signal characteristics are selected to represent the crack size. Next, the validated experiments are conducted to demonstrate the feasibility of the proposed RMFT method in this paper.

Engineering strong man-made cellulosic fibers: a review of the wet spinning process based on cellulose nanofibrils.

With the goal of sustainable development, manufacturing continuous high-performance fibers based on sustainable resources is an emerging research direction. However, compared to traditional synthetic fibers, plant fibers have limited length/diameter and uncontrollable natural defects, while regenerated cellulose fibers such as viscose and Lyocell suffer from inferior mechanical properties. Wet-spun fibers based on nanocelluloses especially cellulose nanofibrils (CNFs) offer superior mechanical performance since CNFs are the fundamental high-performance building blocks of plant cell walls. This review aims to summarize the progress of making CNF wet-spun fibers, emphasizing on the whole wet spinning process including spinning suspension preparation, spinning, coagulation, washing, drying and post-stretching steps. By establishing the relationships between the nano-scale assembling structure and the macroscopic changes in the CNF dope from gels to dried fibers, effective methods and strategies to improve the mechanical properties of the final fibers are analyzed and proposed. Based on this, the opportunities and challenges for potential industrial-scale production are discussed.

Combining transcriptomics and metabolomics to identify key response genes for aluminum toxicity in the root system of Brassica napus L. seedlings.

KEY MESSAGE: By integrating QTL mapping, transcriptomics and metabolomics, 138 hub genes were identified in rapeseed root response to aluminum stress and mainly involved in metabolism of lipids, carbohydrates and secondary metabolites. Aluminum (Al) toxicity has become one of the important abiotic stress factors in areas with acid soil, which hinders the absorption of water and nutrients by roots, and consequently retards the growth of crops. A deeper understanding of the stress-response mechanism of Brassica napus may allow us to identify the tolerance gene(s) and use this information in breeding-resistant crop varieties. In this study, a population of 138 recombinant inbred lines (RILs) was subjected to aluminum stress, and QTL (quantitative trait locus) mapping was used to preliminarily locate quantitative trait loci related to aluminum stress. Root tissues from seedlings of an aluminum-resistant (R) line and an aluminum-sensitive (S) line from the RIL population were harvested for transcriptome sequencing and metabolome determination. By combining the data on quantitative trait genes (QTGs), differentially expressed genes (DEGs), and differentially accumulated metabolites (DAMs), key candidate genes related to aluminum tolerance in rapeseed were determined. The results showed that there were 3186 QTGs in the RIL population, 14,232 DEGs and 457 DAMs in the comparison between R and S lines. Lastly, 138 hub genes were selected to have a strong positive or negative correlation with 30 important metabolites (|R|≥ 0.95). These genes were mainly involved in the metabolism of lipids, carbohydrates and secondary metabolites in response to Al toxicity stress. In summary, this study provides an effective method for screening key genes by combining QTLs, transcriptome sequencing and metabolomic analysis, but also lists key genes for exploring the molecular mechanism of Al tolerance in rapeseed seedling roots.

Equivalent magnetic noise in multi- push-pull configuration magnetoelectric composites: model and experiment.

A theoretical model for the multi-push-pull configuration of magnetoelectric (ME) laminated composites comprising magnetostrictive and piezoelectric layers with interdigitated electrodes encapsulated in polyimide film is presented. Analytical solutions for the ME voltage coefficient αE, ME charge coefficient αQ, noise charge density and equivalent magnetic noise were derived. Parametric studies are presented to evaluate the influence of material properties and polyimide film geometries. The results show that the value of αE was determined by the parameters of the magnetostrictive and piezoelectric phases, and that the values of αQ and noise charge density were determined not only by the component parameters, but also by the volume fraction of the piezoelectric phase and polyimide film geometry. The equivalent magnetic noise had no dependence on the polyimide film geometry, but rather was determined by the component parameters and the volume fraction of the piezoelectric phase. Theoretical and experimental results are compared and shown to have good agreement with each other.

Metglas/Pb(Mg1/3Nb2/3)O3-PbTiO3 magnetoelectric gradiometric sensor with high detection sensitivity.

We developed a novel biaxial magnetoelectric (ME) gradiometer sensor system using Metglas/ Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) laminates for investigation of ac magnetic dipole detection. We demonstrate a detection sensitivity of 20 pT/√Hz in an open environment (unshielded) at quasi-static frequencies with a noise rejection efficiency of 23.5 dB, relative to a uniform external noise. In addition, a signal processing method was used to compute the magnetic field amplitude at a driven frequency of 7 Hz, and the results were also verified by theory. Practical testing and mathematical predictions show that there are only 7.2% and 4.2% gradiometric measurement errors in the x- and y-axis gradiometer components, enabling high-precision target detection.

Differential-mode vibrational noise cancellation structure for Metglas/Pb(Zr,Ti)O3 fiber magnetoelectric laminates.

A differential structure which has the ability to reject external vibrational noise for Metglas/Pb(Zr,Ti)O(3) (PZT) fiber-based magnetoelectric (ME) heterostructures has been studied. This type of ME structure functions better than conventional sensors as a magnetic sensor when used in an environment in which vibrational isolation is impractical. Sensors fabricated with this differential mode structure can attenuate external vibrational noise by about 10 to 20 dB at different frequencies, while simultaneously having a doubled ME voltage coefficient. Interestingly, in addition to offering a means of mitigating vibrational noise, this ME structure offers the potential to be a hybrid sensor, separating magnetic and acoustical signals.

Magnetoelectric bending-mode structure based on Metglas/Pb(Zr,Ti)O3 fiber laminates.

A magnetoelectric (ME) bending-mode structure based on Metglas/Pb(Zr,Ti)O(3) fiber laminates has been studied. This bending mode had a fundamental resonance (FBR) of about 210 Hz, which was much lower than that of the longitudinal mode. Near the FBR, the ME voltage coefficient was about 400 V/cm·Oe. Magnetic sensors based on this bending mode had an equivalent magnetic noise floor of ≤ 0.3 pT/√Hz at f = 210 Hz.

[Study of an optical fiber grating sensor for monitoring corrosion of reinforcing steel].

Based on the principle of the fiber Bragg grating strain sensor as well as the volume expansion of the reinforcing steel due to corrosion, an optical fiber grating sensor for monitoring corrosion of reinforcing steel and the method of temperature compensation were studied in the present paper. The sensor construction is that one Bragg grating is stuck on the inner center of two bars against each other, and the reinforcement volume as well as the diameter will expand due to corrosion. Based upon sensing mechanism, monitoring will be carried out by transforming the diameter increase to the fiber strain, and as a result the degree and rate of reinforcement corrosion can be obtained. The principle of corrosion monitoring is that the strain induced by corrosion and temperature fluctuation is measured by a reinforcing steel fiber grating sensor. At the same time, the strain induced by temperature fluctuation is also measured by an individual stainless fiber grating sensor. Therefore by two independent fiber grating sensors, the volume changed by corrosion can be separated. By the concrete encapsulating and embedding method of FBG corrosion sensor, the degree of corrosion of reinforcing reinforcement will be measured directly, which is not affected by corrosion factors and can be used in the early corrosion monitoring of reinforcement in concrete structures. Finally the relationship between corrosion rate and shift in center wavelength was calibrated by experiment.