Enhancing the lift-off performance of EMATs by applying an Fe3O4 coating to a test specimen

Electromagnetic acoustic transducers (EMATs) are non-contact ultrasonic transducers. The transduction efficiency of a particular EMAT on a given specimen is dependent on the lift-off distance, which is the distance between the EMAT coil and the specimen surface. The transduction efficiency drops dramatically with increased lift-off distance, requiring EMATs to be in close proximity to the specimen, usually within a few millimetres. This paper proposes a new EMAT method of applying an Fe 3 O 4 coating to the test specimen, and quantitatively studying the enhancement effect of Fe 3 O 4 coating on lift-off distance. To eliminate the interference of the electrical and magnetic properties of the tested specimen, a non-magnetic and non-conductive glass specimen is selected. The experimental results on a glass substrate coated with Fe 3 O 4 demonstrate the feasibility of EMATs generating and receiving ultrasonic waves through the coating, by a magneto-elastic mechanism. The transduction efficiency of EMATs on an Fe 3 O 4 coating does not increase linearly with the bias static magnetic field, and the maximum measured signal amplitude value occurs at a relatively low flux density of ~0.12 T. More specifically, it has been shown the Fe 3 O 4 coating can significantly enhance the lift-off distance of EMATs operating at 4 MHz to 8 mm on coated stainless steel. The performance of the Fe 3 O 4 coating can be optimized, showing considerable potential to expand the application range of EMATs

Extending the Incidence Angle of Shear Vertical Wave Electromagnetic Acoustic Transducer with Horizontal Magnetization

Angled shear vertical (SV) waves have been successfully employed in the non-destructive testing of welds, pipes, and railways. Non-contact meander-line coil electromagnetic acoustic transducers (EMAT) have many benefits in generating angled SV waves. The most important benefit is that the incidence angle of an SV wave can be controlled by the excitation frequency. However, the incidence angle of a traditional SV-wave EMAT is reported to be under 45 degrees in many cases. In this work, such cases are tested, and the problems of the received signal at large incidence angles are found to be due to wave interference and small signal amplitudes. An equivalent finite element (FE) model is established to analyze the problem, and the main reason is found to be the head wave. An alternative configuration of angled SV-wave EMAT with horizontal magnetization is proposed to reduce the influence of the head wave. Finally, the results from simulations and experiments show that the proposed EMAT has a larger signal amplitude and significantly reduced interference in large-incidence angle scenarios. Moreover, an incidence angle of an SV wave of up to 60 degrees can be achieved, which will help improve the performance and capability of nondestructive testing

Landscape and research trends of sarcopenic obesity research: A bibliometric analysis

Background: Sarcopenic obesity (SO) is a condition characterized by the coexistence of sarcopenia (loss of muscle mass and function) and obesity. This condition has emerged as a public health concern, particularly with the aging population. Despite an approximately 30-year history of SO research, detailed quantitative analysis of existing research was never undertaken. We aimed to depict the landscape of SO research using bibliometric analysis of literature. Methods: We searched the Web of Science Core Collection on January 15, 2023. The following bibliometric indicators were included: publication trend, the most influential country, the most active discipline, productive institutions, productive journals, prolific and highly cited authors, and highly cited publications. We constructed co-authorship network to explore individual-level, institutional-level, and international-level collaborative patterns in the VOSviewer or Sci2 software. Furthermore, keywords co-occurrence network was extracted by the VOSviewer software, and the burst-detection analysis of keywords was performed using the CiteSpace software. Results: A total of 2023 original articles were retrieved for data analysis. The publications increased dramatically in the last decade. The United States had the highest number of publications on SO (n = 904). The Seoul National University Hospital was the most prolific institution (n = 54) among the 2675 institutions analyzed. As for journals, Clinical Nutrition had the highest number of publications on SO (n = 75). Kim JH was the most prolific author (n = 25), while Cederholm T authored the most cited publication (9381 citations). More than 80 disciplines were involved in SO research, of which, “Geriatrics and Gerontology” was the most activated discipline. The European Working Group on Sarcopenia in Older People (EWGSOP) consensus was the most cited publication (7209 citations). Moreover, the hotspots of SO have been shifting from its biology, prevalence, and risk factors to its outcomes, prognostic factors, complications, and quality of life. Its relationships also evolved from being between SO and aging to being between SO and other diseases. Conclusions: Our study provided a comprehensive landscape of SO research, which may help researchers better identify key information and research trends in this field

Metabolomics and transcriptomics of embryonic livers reveal hypoxia adaptation of Tibetan chickens

Abstract Background Exploring the hypoxia adaptation mechanism of Tibetan chicken is of great significance for revealing the survival law of Tibetan chicken and plateau animal husbandry production. To investigate the hypoxia adaptation of Tibetan chickens (TBCs), an integrative metabolomic-transcriptomic analysis of the liver on day 18 of embryonic development was performed. Dwarf laying chickens (DLCs), a lowland breed, were used as a control. Results A total of 1,908 metabolites were identified in both TBCs and DLCs. Energy metabolism and amino acid metabolism related differentially regulated metabolites (DRMs) were significantly enriched under hypoxia. Important metabolic pathways including the TCA cycle and arginine and proline metabolism were screened; PCK1, SUCLA2, and CPS1 were found to be altered under hypoxic conditions. In addition, integrated analysis suggested potential differences in mitochondrial function, which may play a crucial role in the study of chicken oxygen adaptation. Conclusions These results suggest that hypoxia changed the gene expression and metabolic patterns of embryonic liver of TBCs compared to DLCs. Our study provides a basis for uncovering the molecular regulation mechanisms of hypoxia adaptation in TBCs with the potential application of hypoxia adaptation research for other animals living on the Qinghai-Tibet plateau, and may even contribute to the study of diseases caused by hypoxia

Cut-off frequency analysis of SH-like guided waves in the three-dimensional component with variable width

The component with variable width (such as railway turnout) is one of the most critical configurations in infrastructure. Guided waves have already been employed for flat plates, however, the influence of cross-section width change for guided waves can’t be ignored. In this study, the theoretical cut-off frequency of shear-horizontal (SH)-like guided waves in rectangular plate was analysed. The dispersion curves of rectangular plate with different widths were calculated by the periodic finite element (FE) method. Theoretical calculations and dispersion curves both show that the cut-off frequency of SH-like guided waves decreases when the width of rectangular plate increases. A periodic-permanent-magnet (PPM) electromagnetic-acoustic-transducer (EMAT) at the excitation frequency of 200 kHz was constructed and used in the experiments to generate SH-like guided waves on rectangular plates with the widths of 12 mm and 20 mm, respectively. Experimental results show that multiple wave modes of SH-like guided waves appear as the width of the rectangular plate increases. When the SH-like guided waves propagates in a rectangular plate with variable width, the high-order modes will be cut-off and reflected as the width decreases

Microstructure and Corrosive Wear Properties of CoCrFeNiMn High-Entropy Alloy Coatings

In order to improve the wear resistance of offshore drilling equipment, CoCrFeNiMn high-entropy alloy coatings were prepared by cold spraying (CS) and high-speed oxygen fuel spraying (HVOF), and the coatings were subjected to vacuum heat treatment at different temperatures (500 °C, 700 °C and 900 °C). The friction and wear experiments of the coatings before and after vacuum heat treatment were carried out in simulated seawater drilling fluid. The results show that CoCrFeNiMn high-entropy alloy coatings prepared by CS and HVOF have dense structure and bond well with the substrate. After vacuum heat treatment, the main peaks of all oriented FCC phases are broadened and the peak strength is obviously enhanced. The two types of coatings achieve maximum hardness after vacuum heat treatment at 500 °C; the Vickers microhardness of CS-500 °C and HVOF-500 °C are 487.6 and 352.4 HV0.1, respectively. The wear rates of the two coatings at room temperature are very close. CS and HVOF coatings both have the lowest wear rate after vacuum heat treatment at 500 °C. The CS-500 °C coating has the lowest wear rate of 0.2152 mm3 m−1 N−1, about 4/5 (0.2651 mm3 m−1 N−1) of the HVOF-500 °C coating. The wear rates and wear amounts of the two coatings heat-treated at 700 °C and 900 °C decrease due to the decrease in microhardness. The wear mechanisms of the coatings before and after vacuum heat treatment are adhesive wear, abrasive wear, fatigue wear and oxidation wear

Effects of doping ceria on flame quenching in a narrow channel with zirconia-based functional coatings

Wall coating modification has been a potential solution to organize the combustion process in space-constrained system. For this purpose, CeO2 doping effects on the flame stability of premixed methane/air mixtures confined within an adjustable-gap narrow channel with coating ZrO2-based ceramics are experimentally investigated. A series of characterization means are utilized to analyze these prepared composite coatings. Results elaborate that the catalytic activities of CeO2-ZrO2 solid solution correlate with the ratio of CeO2 dopant in bulk. Phase structural stabilities can be strengthened through increasing the CeO2 content, which is due to the significant increase in the ratio of tetragonal phase to monoclinic phase of ZrO2. X-ray photoelectron spectroscopy and H2 temperature-programmed reduction analysis outcomes show that the concentration of formed oxygen vacancies increases significantly with richer CeO2 phase doped, which promotes the exaltation of lattice oxygen activity and fluidity. Flame quenching tests demonstrate that the wall surface temperature dependence of the quenching distance is changed substantially by doping CeO2 into the ZrO2 coating wall, eliminating the negative temperature effect observed for a pure ZrO2 case at the medium temperature ranges of 673-773 K. The cases of higherCeO2-content doping provide a lower flame quenching distance, especially at slightly fuel-rich conditions, which arises from the enhancement of the storage and release functions of highly active oxygen ions through Ce4+/Ce3+ redox cycles. Comparing of OH planar laser-induced fluorescence images near the extinction limit indicates that in addition to flow rate and air-fuel ratio, different coating materials also have dramatic effects on the post flame characteristic and flame oscillation. In general, this paper not only provides a good overview of the chemical interaction between the wall and flame, but also makes an implication for the design of high-stability small-scale combustors by reasonably manufacturing this type of CeO2-ZrO2 coating functional materials

An Integrated Modelling Approach for Flood Simulation in the Urbanized Qinhuai River Basin, China

The accurate simulation and prediction of flood response in urbanized basins remains a great challenge due to the spatial and temporal heterogeneities in land surface properties. We hereby propose an integrated modelling approach that consists of a semi-distributed conceptual hydrological model and a novel parameterization strategy. The modelling approach integrates the Xinanjiang (XAJ) model, Taihu Basin (TB) model, and Nash instantaneous unit hydrograph (IUH) into a framework. Model parameters are calibrated by optimizing their relationships with corresponding physical factors. The proposed modelling approach is applied in the Qinhuai River basin (QRB), China. The modelling approach shows satisfactory performance in flood simulation both for calibration and validation of flood events in the QRB. The approach has temporal and spatial prediction capability by using the established relationships between parameter values and physical factors. Robustness analysis reveals that the different sets of flood events used for parameter relationship calibration led to similar model performance. Numerical experiments show that impervious coverage poses strong influences on the model performance and needs to be considered in flood routing simulations for small- or medium-intensity flood events

Unconventional correlated insulator in CrOCl-interfaced Bernal bilayer graphene

The realization of graphene gapped states with large on/off ratios over wide doping ranges remains challenging. Here, we investigate heterostructures based on Bernal-stacked bilayer graphene (BLG) atop few-layered CrOCl, exhibiting an over-1-GΩ-resistance insulating state in a widely accessible gate voltage range. The insulating state could be switched into a metallic state with an on/off ratio up to 107 by applying an in-plane electric field, heating, or gating. We tentatively associate the observed behavior to the formation of a surface state in CrOCl under vertical electric fields, promoting electron-electron (e-e) interactions in BLG via long-range Coulomb coupling. Consequently, at the charge neutrality point, a crossover from single particle insulating behavior to an unconventional correlated insulator is enabled, below an onset temperature. We demonstrate the application of the insulating state for the realization of a logic inverter operating at low temperatures. Our findings pave the way for future engineering of quantum electronic states based on interfacial charge coupling

deepflowio/deepflow: v6.4.1

<p>Release v6.4.1</p&gt