Skin depth and detection ability of magneto-optical imaging for weld defects in alternating magnetic field

To detect and evaluate weld defects, the skin depth and detection ability of magneto-optical imaging (MOI) for weld defects in alternating magnetic field were studied, and the application scope of MOI in alternating magnetic field was determined. A model of magnetic flux leakage testing (MFL) for weld defects is established by finite element method, and the reliability of the model is determined by law analysis and MOI experimental verification. Comparing MFL and eddy current detection with simulation method, the skin effect mechanism and rules of MOI for weld defects in alternating magnetic field are analyzed and obtained. Considering the effect of skin effect, different MFL detection models are established, and the detection ability of MOI for weld defects with different frequencies under corresponding models is studied and obtained. Finally, the MOI experiment is used to verify the results, which are consistent with the simulations. The skin effect rule and detection ability of MOI for weld defects obtained by simulation method can be used as the theoretical basis for practical experiments.     

Microemulsion synthesis of ms/tz-BiVO4 composites: The effect of pH on crystal structure and photocatalytic performance

In this work, BiVO₄ composites, containing the tetragonal zircon phase (tz-BiVO₄), and monoclinic scheelite phase (ms-BiVO₄), were synthesized using the microemulsion method. The effect of pH on phase composition and photocatalytic activity were investigated. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), a ms/tz-BiVO₄ composite forms at pH = 1.0 and pure ms-BiVO₄ is obtained in the pH range 4.0–10.0. The three primary steps in preparing BiVO₄ were monitored by optical microscopy and the role played by the microemulsion on the phase composition of BiVO₄ is explained. Photoluminescence spectroscopy (PL), UV–visible diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the physical and chemical properties of BiVO₄ composites. The composite formed at pH = 1 exhibited the lowest hole-electron (h⁺-e^-) recombination rate, resulting in the highest photocatalytic activity towards microcystin-LR (MC-LR), with near 100% removal of MC-LR in 5 h. ESR and trapping experiments indicated that MC-LR degradation was mediated primarily by hydroxyl radicals (•OH), superoxide radicals (O₂^•−) and photogenerated holes (h⁺).     

智能远距离激光切割控制系统设计与研究

随着人工智能技术的发展,机器视觉与传统工业的结合应用越来越广泛。在电力铁塔安装作业过程中,角钢预置孔位常出现错位,需要在高空实施切割打孔作业。因激光切割角钢效率较高,研制了一套适用于高空铁塔的扩孔切割设备可解决传统方法效率低的问题。通过视觉识别待切割孔,确定待切割路径,控制电机转动,完成激光切割作业。经过试验,所设计的控制系统能够满足激光扩孔切割要求。     

Users in the design of Hydrogen Energy Systems: A systematic review

The energy transition is a major societal issue to which hydrogen energy can make an important contribution. If the technical aspects of hydrogen energy seem paramount, it is also important to focus on the end users of these future systems. Indeed, users play an important role in the success of energy systems: they may not accept it, they may not use it as intended. But not only, users can also be a source of innovation. Thus, it is possible to mobilize different approaches, which if they are all legitimate, do not have the same efficiency. In this systematic review of the literature, which combines lexical analysis and data analysis of 152 publications, we identify the approaches implemented to take into account users in Hydrogen Energy Systems. Our results indicate that final users are mostly perceived as a barrier to the deployment of Hydrogen Energy Systems, or as a parameter to be assessed rather than as a resource for the design. Researches have mainly the aim of improving technology adoption. Since Hydrogen Energy Systems are emerging, we recommend focusing studies on upstream user research aimed at stimulating and enhancing technologies and systems design. We also recommend increasing the share of study which focus on the case of hydrogen energy stationary applications and buildings.     

2D Ti3C2Tx MXene/aramid nanofibers composite films prepared via a simple filtration method with excellent mechanical and electromagnetic interference shielding properties

Electromagnetic shielding (EMI) materials are becoming more and more important because of the increasingly serious radiation pollution. The preparation of high mechanical strength, ultrathin, lightweight, flexible materials with excellent EMI shielding performance have so far been elusive. Here, we try to prepare an ultrathin, lightweight and flexible film with excellent EMI shielding performance using one-dimensional aramid nanofibers (ANFs) and two-dimensional few-layered Ti₃C₂T_x through a simple filtration method. The ultimate tensile strength and strain of the film are up to 116.71 MPa and 2.64%. The EMI shielding effectiveness and the specific EMI shielding efficiency are 34.71 dB and 21971.37 dB cm² g⁻¹, which will be no recession after 1000 times bending. Our results show that a practical EMI shielding material with excellent performances has been successfully prepared, which will be widely applied in wearable electronics, robot joints, and precision instrument protection and so on.     

Some molecular aspects of hydrogen production by marine Chlorella pyrenoidosa under nitrogen deprivation condition in natural seawater

In this study, marine microalgae Chlorella pyrenoidosa produced 186 ml H₂/l under nitrogen deprivation in natural seawater, and adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to medium reduced the total volume of hydrogen production by 85%. This suggested water was the main electron donor for hydrogenase. An active starch accumulation was observed during the first two days in nitrogen deprivation. But the starch content in cell decreased only by 7% at the end of the hydrogen evolution stage. This was shown the absence of a large contribution of starch to the hydrogen production by C. pyrenoidosa in nitrogen deprivation. Different from the hydrogen production by Chlamydomonas reinhardtii under sulfur deprivation condition, the concentration of acetate in the medium decreased not only at the stage of oxygen consumption but also during the stage of hydrogen evolution by C. pyrenoidosa. Thus, acetate is involved not only in the establishment of anaerobiosis but also plays an important role in the production of hydrogen by C. pyrenoidosa as an exogenous electron donor.     

Synthesis method of novel Gd2O3@Fe3O4 nanocomposite modified by dextrose capping agent

In current study, gadolinium oxide was heterogeneously formed on the surface of iron oxide nanoparticles and further modified with dextrose capping agent to be used in biomedical applications, especially for contrast enhancement in MR images. First, two types of iron oxide nanoparticles were prepared at 25 and 80 ^°C via simple coprecipitaion method. Then, gadolinium oxide nanoparticles were synthesized through a consecutive precipitation process on previously formed iron oxide seeds in an aqueous media and subsequent annealing at 300 ^°C. Finally, dextrose was used as capping agent to stabilize nanocomposites in a colloidal suspension. X-ray diffraction (XRD), Scanning and Transmission electron microscopy, Dynamic Laser Scattering (DLS), Fourier-Transform Infrared Spectroscopy (FTIR), and Magnetometery (VSM) techniques were employed for nanocomposites investigation and MTT-assay method used for viability assessment of colloidal samples. Measurements based on Scherrer equation from XRD patterns showed that increasing coprecipitation temperature resulted bigger iron oxide crystallites. The iron oxide crystallite size was increased from 15.1 to 28.1 nm. Precipitation process led to gadolinium oxide formation with 30.7 and 38.8 nm crystallite sizes, respectively. TEM images revealed that iron oxide agglomerates were encapsulated in gadolinium oxide surroundings. Hydrodynamic size of the coated nanoparticles with dextrose was 208 and 247 nm. In VSM examinations, nanocomposites did not display coercive field and the saturation magnetization was 1.93 emu/g. MTT-assay results showed 80% viability in 285 μg nanocomposites containing 96.9 μg [Fe] and 11.4 μg [Gd].     

First demonstration of photoelectrochemical water splitting by commercial W–Cu powder metallurgy parts converted to highly porous 3D WO3/W skeletons

Hydrogen evolution through photoelectrochemical (PEC) water splitting by tungsten oxide-based photoanodes, as a stable and environmental-friendly material with moderate band gap, has attracted significant interest in recent years. The performance of WO₃ photoanode could be hindered by its poor oxygen evolution reaction kinetics and high charge carrier recombination rate. Additionally, scalable and cost-effective commercial procedure to prepare nanostructured electrodes is still challenging. We present, for the first time, a novel and scalable method to fabricate highly efficient self-supported WO₃/W nanostructured photoanodes from commercial W–Cu powder metallurgy (P/M) parts for water splitting. The electrodes were prepared by electrochemical etching of Cu networks followed by hydrothermal growth of WO₃ nanoflakes. Interconnected channels of W skeleton provided high active surface area for the growth of WO₃ nanoflakes with a thickness of ~40 nm and lateral dimension of ~250 nm. The optimized photoelectrode having 35% interconnected porosity exhibited an impressive current density of 4.36 mA cm⁻² comprising a remarkable photocurrent of 1.71 mA cm⁻² at 1.23 V vs. RHE under 100 mW cm⁻² simulated sunlight. This achievement is amongst the highest reported photocurrents for WO₃ photoelectrodes with tungsten substrate reported so far. Impedance and Mott-Schottky analyses evidenced fast charge transfer, low recombination rate, and accelerated O₂ detachment provided by optimum 3D porous WO₃/W electrode. Due to the nature of the commercial P/M parts and low-temperature hydrothermal processing, the procedure is cost-effective and scalable which can pave a new route for the fabrication of highly porous and efficient water splitting electrodes.