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The magnetic flux leakage (MFL) defect detection of oil and gas pipelines faces two tasks, defect type identification and defect size and shape estimation. However, there are few pieces of research on defect shape estimation, especially fewer research works on defect cross-sectional profile estimation. The complex nonlinear relationship between the defect profile and the MFL signal makes the defect profile difficult to be estimated. In this article, we propose a novel visual deep transfer learning (VDTL) neural network, which not only predicts the defect size but also estimates the defect cross-sectional profile. VDTL network consists of a visual data transformation layer, a transfer learning convolutional neural network (CNN) layer, and a fully connected layer. In addition, we propose an augmentation data to figure (ADF) transformation method for one-dimensional MFL signals, and a fusion algorithm for two-dimensional radial and axial MFL images, which enriches the defect information in the images. Based on the Alexnet network, the multikernel maximum mean discrepancy (MK-MMD) transfer learning algorithm is introduced to improve the accuracy. Experiments are carried out on the data collected in the laboratory and on the data simulated by the finite element method. The results show that the prediction errors for defect length, depth, and defect cross-sectional profile are 0.67 mm, 0.97%, and 2.67%, which are the smallest among the other methods. The research provides a theoretical basis for accurate defect prediction and the safe maintenance of oil and gas pipelines.

A ladder-shape melting temperature isothermal amplification (LMTIA) assay was established and used to detect soybean components in edible oils. LMTIA primers were designed with the sequence of the internal transcribed spacer (ITS) gene as the target, the reaction temperatures were optimized, the sensitivity was determined, and the suitability of the DNA extraction method for edible oil was assessed, with H2O and genomic DNA (gDNA) from corn, rapeseed, cottonseed, sesame, chili, chicken, pork, beef, and mutton as negative controls to test the false positives of the LMTIA assay. The established LMTIA assay gave a sensitivity of 1 pg at an optimal temperature of 57 °C. The Edible Oil DNA Extraction Kit was suitable for the LMTIA assay to detect soybean components in refined plant oil. No false positives occurred from all negative controls. This study successfully established the LMTIA assay for the detection of soybean ITS genes in edible oils, which could be used to detect soybean components in edible oils.

AbstractThe ladder-shape melting temperature isothermal amplification (LMTIA) is a newly developed technique with advantages of simple mechanism, easy primer design, quick turn-around time, high specificity, high sensitivity and short target sequence compared to the loop-mediated isothermal amplification (LAMP) technique. The objective of this research was to establish the LMTIA assay for detection of chicken in beef. The LMTIA primers targeting the prolactin receptor gene of Gallus galluswere designed, the LMTIA reaction system was optimized, the specificity and the sensitivity of the LMTIA assay were determined. Our results showed that the LMTIA assay was able to specifically detect 100 ng genomic DNA of Gallus gallus, without detecting the 100 ng genomic DNA of Anas platyrhynchos, Felis catus, Sus scrofa, Canis lupusfamiliaris, Bos taurusor Capra hircus. The sensitivity of the LMTIA assay was 100 pg genomic DNA of G. gallus. Furthermore, the LMTIA assay was able to detect the chicken adulterated in beef with ≥0.1% (w/w) detection limit (LOD). This study holds a promise for facilitation of the surveillance of the commercial adulteration of chicken in beef.

Ladder-shape melting temperature isothermal amplification (LMTIA) is a newly developed technology, and the objective of this study was to establish its effectiveness for detection of duck adulteration in beef. LMTIA primers were designed with the prolactin receptor gene of Anas platyrhynchosas the target. The LMTIA reaction system was optimized, and its performance was compared with that of the loop-mediated isothermal amplification (LAMP) assay in terms of specificity, sensitivity, and limit of detection (LOD). Our results showed that the LMTIA assay was able to specifically detect 10 ng of genomic DNAs (gDNAs) of A. platyrhynchos,without detecting 10 ng of gDNAs of Bos taurus, Sus scrofa, Gallus gallus, Capra hircus, Felis catus,and Canis lupus familiaris. The sensitivity of the LMTIA assay was 1 ng of gDNAs of A. platyrhynchos; it was able to detect duck adulteration in beef with a 0.1% LOD. Although the LAMP assay could not clearly distinguish A. platyrhynchosfrom G. gallus,it had a sensitivity of 10 ng of gDNAs of A. platyrhynchosand a LOD of 1% duck adulteration in beef. This study may help facilitate the surveillance of commercial adulteration of beef with duck meat.

Subsea umbilical cable is an important link to transmit power and signals in subsea production system, often lasts for tens of kilometers in deep-sea projects. It is expensive, bulky, and inconvenient to transport. In this article, a compact, low-cost umbilical cable electrical simulator is proposed, which can be equivalent to the real umbilical cable in power transmission characteristics and can adjust parameters in a certain range. By studying the electrical transmission characteristics of long umbilical cable, the calculation method of electrical transmission characteristics is determined. A simulation device for simulating the transmission characteristics of umbilical cable is designed, which can be used to simulate the umbilical cable diameter of 10 and 16 mm2. The voltage drop characteristics, signal transmission attenuation characteristics, and power carrier characteristics of the umbilical cable electrical simulation device are simulated and experimentally analyzed. The experimental results show that the voltage drop characteristics, signal transmission attenuation characteristics, and power carrier characteristics of the umbilical cable electrical simulator are in good agreement with the real umbilical cable. The simulation device of umbilical cable can well simulate the power and signal transmission characteristics of real umbilical cable.

MXene is a new type of two-dimensional (2D) material that finds wide applications; however, its adhesion and tribological properties have not yet been fully revealed. Here, the chemical structure of MXene was revealed by X-ray diffraction, and the adhesion and friction behaviors of MXene were studied with atomic force microscopy (AFM) Nanoman technology. It was found in AFM tests that MXene exhibited enhanced adhesion and friction at higher pressure but exhibited reduced adhesion and friction at elevated temperature, while the sliding speed and delay time of the AFM probe have negligible effects on the friction. X-ray photoelectron spectroscopy was used to reveal the change in the chemical structure of MXene at different temperatures. We found increased oxidation, and replacement of C by O atoms occurred on MXene at higher temperatures, which has a profound impact on the adhesion and friction between MXene and the probe tip. This discovery lays the foundation for understanding the adhesion mechanism and the dynamic adhesion behavior in friction of MXene, rendering MXene a much broader application prospect.

Tools abrasive wear due to sand particles has caused severe damage during oil and gas exploitation. The friction and wear behaviors of single quartz sand particle against N80 casing steel were investigated to estimate the particle transport resistance and particle abrasive wear behavior using a homemade tribometer in wellbore sand cleanout. Various measurements were conducted to research the impact factor of particle under different water processing condition, dry, short immersion, wet, influences of load and slide velocity. Experimental results indicated that particle-casing friction resistance is mainly formed due to plowing and adhesion effect. Casing transfer and plowing removal are two main damage forms. Particle real contact area increases noticeably after water absorption, which decreases the hertz contact stress and finally produces less plowing depth of casing steel and causes less damage. With load increasing, friction resistance and wear increase with addition of plowing depth. A simple particle-casing friction model was established considering the experimental contact behavior.

Multilayer graphene platelet and expanded graphite were deposited on alumina disk surface and their effects on tribological performance of an alumina–alumina contact in different environments were evaluated using a pin-on-disk tribometer. Experimental results indicate that coefficients of friction at the contact are reduced by deposited particles due to their lubricating effect. It is interesting to find that wear of the contact in dry conditions is less than that under liquid lubrication. Tribofilm plays a key role in the wear reduction performance. In liquid media, however, formation of tribofilm is limited due to fluid flow and formed thin tribofilm is not able to protect the contact from wear. Experimental results show that formation of tribofilm is improved by both multilayer graphene platelet and expanded graphite. This is attributed to the higher adhesion force between graphene and alumina than that between alumina and alumina. The findings demonstrate that deposition of graphene-based materials onto alumina surface hold the promise of providing a new pathway to increase the anti-wear performance of alumina and possibly other ceramics.

As a device with excellent potential, the quartz crystal microbalance (QCM) has been developed to study the interfacial properties of liquids, such as adsorption/desorption kinetics, electrochemical reaction mechanisms and interfacial viscosity. In this research, the adsorption properties of cationic polyelectrolytes (poly(diallyl dimethylammonium chloride) and poly(allylamine hydrochloride)) on solid surfaces were observed using QCM. The results indicated that the response to adsorption was different with a change in polyelectrolyte solution concentration and that the frequency shift increased as the solution concentration increased. The adsorption of the polyelectrolyte also depends on the solid surfaces and solution pH values. Furthermore, the change in the molecular conformation of the polyelectrolyte molecules is the main factor that affects the adsorption properties and structures.

Particles deposition and plug-in wellbore cause lots of damage and efficiency reduction during oil and gas exploitation. Transportation has been a focus for safety and production improvement. The annular flow field and particles transport behavior have been investigated using computational fluid dynamics with an renormalization group k–ɛ method. Effects of particles volume concentration, washing fluid concentration with power-law shearing, annular eccentricity, flow rate, and rotation speed have been researched to get the mechanism of particles accumulation and transport behavior. The results show that an increase in eccentricity causes velocity reduction of the annular narrow gap area, particles easily deposit, accumulate, and are hard to transport; increasing flow rate and fluid concentration apparently improve particles transportation and reduce deposition, pressure loss increases; inlet particles volume concentration increases deposition starting position and deposition length, the inner pipe rotation facilitates particles’ second suspension.

The daisy chain is one of the main layout types of the subsea production system in the development of deepwater oil and gas fields. The number of production loops, length of subsea pipelines, and partition of subsea wells are the main concerns in pigging loop design, pipeline laying, and flow assurance, which become important factors for the capital and operating expenditures and the risk management of deepwater fields. This article focuses on the basic optimal partition problem of production loops for subsea wells in the layout of daisy chains. It proposes to find the optimal partition method at the lowest layout cost, where a mathematical model is proposed and its dedicated algorithm is developed. Numerical simulations are conducted to evaluate the validity of the proposed model and the performance of the algorithm. The results show that the model can accurately describe the optimal partition problem of daisy chains in practice, and a mathematical solution to the optimal partition can be obtained by the algorithm programmed in MATLAB, which can provide the engineers a quantitative reference for the layout of daisy chains in engineering.

Elastic rubbers are widely used in nature and engineering. In order to better understand soft rough contact under dry and wet conditions during deepwater pipelaying process, various polyurethane (PU) discs both in PU-pipe and PU-steel sliding combinations have been investigated by using self-developed tribometer. The tribological test results show that the friction coefficient can be clearly seen: PU90< PU80 < PU70, under dry conditions. Experimental results also indicate that the two dramatic increases of the frictional coefficient exist in the rough soft PU-pipe contact. The potential influence of asperities and thin liquid film is discussed.

The umbilical cable tensioner is a core component of deep-water oil and gas development, and it can lay and recover the umbilical cables to ensure the transmission of communication signals, electric signals or liquid injection. The displacements of tensioner’s clamping hydraulic cylinders, which are not synchronized as the nonlinear electro-hydraulic control system, results in the occurrence of the crawler mechanism’s stuck phenomenon or cause umbilical cable deformation or even cause damage by the extrusion in the umbilical cable’s clamping process. To ensure synchronous clamping, the structure scheme of umbilical cable tensioner, crawler mechanism, clamping mechanism and the hydraulic system of synchronous clamping control is designed in this study. This article also analyzes the function of structure parameters and hydraulic cylinders’ displacement, speed and acceleration, and builds the synchronous clamping mechanical model to reveal crawler mechanism’ clamping law. The study proposes the control strategy including the fast moving stage, the working stage and the pressuring stage based on proportional–integral–derivative control, and analyzes the characteristics of synchronous clamping control by building the synchronous clamping experimental platform in the lab environment. The experimental data shows that the tensioner’s hydraulic cylinders have excellent synchronous clamping performance and the theoretical analysis is feasible. The research has important guiding significance for the tensioner design, and provides theoretical support for the laying of the deep-sea umbilical cables.

In order to better understand linear polymer aqueous solutions in soft lubrication from boundary to mixed lubrication, poly(ethylene glycol) and sodium hyaluronateare used as model polymers were investigated by using UMT-2 tribometer with the ball-on-disk mode. The relationship between the master Stribeck curves of the polymer aqueous solutions and the influence factors were investigated. Experimental results indicated that soft lubrication is determined by lubricant rheological properties and surface-lubricant interactions, e.g., wetting behavior of polymer aqueous solution on tribological surfaces.

Abstract: The ultrathin polyelectrolyte molecular deposition films and polyelectrolyte composite nanoparticles molecular deposition films were prepared using layer-by-layer molecular deposition method and in situ growth method. A micro-tribometer has been developed to measure the shear response of those ultrathin molecular deposition films. By using a smooth steel sphere in a ball-on-flat configuration, the shear force was determined for molecular deposition films on glass substrate for different layers. The results indicate that the shear behaviors of molecular deposition film were mainly determined with the contact area and film layers. Moreover, the composite molecular deposition film with nanoparticles has better shear behaviors than the polyelectrolyte molecular deposition film. The shear force of polyelectrolyte molecular deposition film is more dependent on the speed than that of composite nanoparticle molecular deposition film.

An overview of the advances in studies on tribology of molecular deposition (MD) films is presented here to summarize the studies of nanofrictional properties, adhesion, wear and mechanical behavior, as well as the molecular dynamics simulation of nanotribological properties of the film in the last decade. Some key research topics which need to be investigate further are addressed.

A novel method, termed ladder-shape melting temperature isothermal amplification (LMTIA), was developed in this study. As a proof of concept, one pair of primers or two pairs of nested primers and a thermostable DNA polymerase were employed to amplify the internal transcribed spacer of Oryza sativawith the ladder-shape melting temperature curve. Our results demonstrated that the LMTIA assay with nested primers was 50-fold more sensitive than the LAMP assay with the same level of specificity. The LMTIA method has the potential to be used for the prevention and control of emerging epidemics caused by different types of pathogens.

The subsea wellhead connector is an essential piece of equipment whose successful metal-to-metal sealing capacity is crucial to produce deep-sea oil and gas safely. This paper analyzed the mechanical behavior of the metal seal ring in the subsea wellhead connector under preload and operating conditions while determining the role of contact stress in the theoretical relationship between the seal ring and the structural parameters, as well as working pressure. Theoretical calculations and the finite element method were used to analyze the effects of preload force, contact width, preload compression, and working pressure on contact stress. The results derived from the finite element approach were consistent with those obtained with the theoretical calculation method. Finally, the contact width and preload compression parameters of the metal seal were tested by constructing a test device to evaluate the metal seal of the subsea wellhead connector. The relationship between the preload force, contact width, and preload compression was analyzed, and the maximum sealing pressure under different preload forces was investigated. The results verified the accuracy of the theoretical and finite element calculations. This paper proposed the theoretical calculation method for designing and analyzing the metal seal of the subsea wellhead connector.