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Abrupt transverse ground movements induced by landslide, strike-slip offset, and excavation can exert excessive soil restraints on buried pipes and threaten the pipe safety. The determination of lateral soil restraint is, therefore, a key factor for the evaluation of buried pipes in such areas. However, effective analysis solutions to assess the area of failure zone of surrounding soils and to estimate the soil resistance on pipes are still limited. In this work, an improved implicit limit equilibrium model is proposed to calculate the ultimate lateral soil restraint of buried pipes in dry sand, in which the effect of active soil wedge is considered, and the heights of equal settlement plane in both passive and active wedges can be estimated. Comparisons are made between collected physical modeling results and calculations from different methods. Results show that the proposed method yields a better approximation to the measured data. Parametric studies are subsequently conducted, which illustrate that the ultimate soil lateral restraint is influenced by the pipe diameter, internal friction angle, and constrained modulus of soil. The influence of effective soil unit weight is minimal. The proposed method is beneficial for safety evaluation of buried pipes subject to lateral dragging. Key words: buried pipe, arching effect, soil restraint, limit equilibrium, equal settlement plane, Introduction Buried pipelines are one of the most efficient means for transporting living products for human society, including fresh and waste water, heat, electricity, oil, and natural gas. As buried [...]

Heat exchangers play an important role in offshore oil and gas production and offshore low-temperature waste heat power generation. Heat exchanger health management mainly relies on performance parameter monitoring; however, accurate fault mode identification remains a challenge and the diagnostic results are difficult to interpret. This paper proposed an interpretable intelligent diagnosis method for heat exchangers based on Shapley Additive exPlanation and eXtreme Gradient Boosting. Firstly, secondary parameters characterizing the health state of heat exchangers are constructed based on online monitored data such as pressure and temperature. Then, the multi-dimensional feature vector is constructed by integrating the online monitored data and secondary parameters. The XGBoost fault diagnosis model for leakage and scaling faults is established with the multi-dimensional feature vector as the input. To improve the model performance on diagnosis, a grid search optimization algorithm is adopted. After the fault diagnosis of a heat exchanger is completed, the SHAP method is introduced to analyze the contribution of features by quantifying their influence on the fault diagnosis results. Finally, the effectiveness of the proposed method is verified by the heat exchanger fault simulation experiment. The proposed method achieved a diagnosis accuracy of 99.79%, which has better performance than the traditional fault diagnosis method. [ABSTRACT FROM AUTHOR]

Heat exchangers play essential roles in the oil and gas production process for convective heat transfer and heat conduction. The health management of heat exchangers stays in the direct monitoring of performance parameters. Aiming at the difficulty of precise fault identification and quantification for heat exchangers in multiple unknown failure modes, a data-model fusion-driven fault quantitative diagnosis method is proposed. Firstly, based on the monitoring data such as temperature, pressure and flow rate, the secondary parameters characterizing the heat exchanger running state are constructed combined with structural physical parameters. Then, by analyzing the correlation among parameter variation, failure modes and deterioration degree, a qualitative inference model of heat exchanger is formed for fault identification, where weights of parameters are introduced based on their sensitivity for different failure modes. After the fault mode is identified, to achieve quantitative analysis of the failure degree, an index-integrated mechanism equation is constructed using monitoring data and secondary parameters, where the index is dynamically modified by online data. Finally, a heat exchanger experiment is carried out to demonstrate the robustness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

The charging and discharging of satellite surfaces induced by the space plasma environment constitute a primary cause of spacecraft anomalies, particularly in geosynchronous orbits subject to geomagnetic substorms and hot plasma injections from the magnetotail, where satellites are prone to unequal high-potential charging, significantly impacting the safe and reliable operation of spacecraft. Addressing the need for measuring these unequal charge states, a high-precision, wide-range spacecraft potential measurement method based on capacitive voltage division was investigated. This study analyzed the mechanism of potential measurement and the factors contributing to errors during the measurement process, explored optimal design methodologies, and innovatively developed a fundamental charge zeroing method to resolve output drift issues caused by accumulated errors fundamentally. Consequently, a non-contact potential measurement system was developed, featuring a measurement range of up to −15,000 V, a resolution below 15 V, and a nonlinear error of less than 0.1%. This system provides technical support for monitoring the potential state of spacecraft and ensuring their safety and protection. [ABSTRACT FROM AUTHOR]

Joint kinematic behaviour, i.e., joint rotation and axial translation, can partially help pipelines to accommodate abrupt ground movements, and cause leaking if joint service limit is exceeded, even without any structural failure. Kinematic behaviour of bell-spigot jointed ductile iron (DI) pipes and its influence on joint sealing capacity under abrupt transverse ground movements are investigated in this study. Firstly, a beam-on-spring finite element analysis on joint kinematics of DI pipes is conducted, in which different fault-pipe crossing positions are implemented. Based on simulated results, a modified joint kinematic solution incorporating pipe deflection and joint shear force under different fault-pipe crossing positions is proposed. Then, a Monte Carlo simulation (MCS)-based reliability assessment procedure for joint sealing capacity is developed. Sensitivity analysis is subsequently conducted to investigate the effects of uncertainties associated with initial axial translation, soil properties, and crossing positions on the joint sealing capacity, and the effects of different deterministic solutions are compared. The proposed method allows engineers to effectively evaluate how the joint sealing capacity of DI pipes changes with consideration of uncertainties when abrupt transverse ground movements are encountered. Key words: bell-spigot joint, ductile iron pipeline, strike-slip offset, joint leaking, reliability. Le comportement cinematique de joint, c'est-a-dire la rotation et la translation axiale de joint, peut aider partiellement les pipelines a s'adapter aux mouvements brusques du sol et provoquer des fuites si la limite de service des joints est depassee, meme en l'absence de toute defaillance structurelle. Cette etude examine le comportement cinematique des tuyaux en fonte ductile (DI) assembles a emboitement et son influence sur la capacite d'etancheite des joints en cas de mouvements transversaux brusques du sol. Tout d'abord, une analyse par elements finis de type 'poutre sur ressort' sur la cinematique des joints des tuyaux DI est realisee, dans laquelle differentes positions de croisement entre les tuyaux et la faille (<>) sont mises en reuvre. Sur la base des resultats de la simulation, une solution cinematique modifiee des joints integrant la deflexion de tuyaux et la force de cisaillement du joint dans differentes positions de croisement entre les tuyaux et la faille est proposee. Ensuite, une procedure d'evaluation de la fiabilite de la capacite d'etancheite des joints basee sur la simulation de Monte Carlo (MCS) est developpee. Une analyse de sensibilite est ensuite realisee pour etudier les effets des incertitudes associees a la translation axiale initiale, aux proprietes du sol et aux positions des croisements sur la capacite d'etancheite des joints, et les effets de differentes solutions deterministes sont compares. La methode proposee permet aux ingenieurs d'evaluer efficacement comment la capacite d'etancheite des joints des tuyaux DI change en tenant compte des incertitudes lorsque des mouvements transversaux abrupts du sol sont rencontres. [Traduit par la Redaction] Mots-cles: joint a emboitement, canalisation en fonte ductile, decalage du decrochement, fuite du joint, fiabilite., 1. Introduction Buried water pipelines are geographically distributed systems that include pipelines of numerous kilometres in length, and they are composed of segments assembled by flexible connections such as bell-spigot [...]

Highly sensitive protein biomarker detection is critical for the diagnosis of gastric cancer (GC), however the accurate and sensitive detection of low-abundance proteins in early-stage GC is still a challenge. Herein, a surface-enhanced Raman scattering frequency shift assay was performed on a developed microfluidic chip for the detection of GC protein biomarkers carcinoembryonic antigen (CEA) and vascular endothelial growth factor (VEGF). The chip is made up of three groups of parallel channels and each parallel channel consists of two reaction regions, enabling the simultaneous analysis of multiple biomarkers in multiple samples. The presence of CEA and VEGF in the sample can be captured by the 4-mercaptobenzoic acid (4-MBA)-conjugated antibody functionalized gold nano-sheet (GNS-) substrate, resulting in the Raman frequency shift. As a result, a typical Raman frequency shift of 4-MBA presented a linear relationship with the concentration of CEA and VEGF. The limit of detection (LOD) of the proposed SERS microfluidic chip reaches as low as 0.38 pg mL−1 for CEA and 0.82 pg mL−1 for VEGF. During the detection process, only one step of sample addition is involved, which eliminates the multiple reaction step-induced nonspecific adsorption and significantly increases the convenience and specificity. In addition, serum samples from GC patients and healthy subjects were tested and the results were in good agreement with the current gold-standard method ELISA, suggesting the potential application of the SERS microfluidic chip in clinical settings for early diagnosis and prognosis of GC. [ABSTRACT FROM AUTHOR]

Submarine telecommunication cables, which carry about 99% of international telecommunications, are usually buried shallowly beneath seabed and vulnerable to seabed movements. In recent years, many submarine cable damages have been observed when significant lateral seabed movements occur due to geohazards, e.g., offsets of strike-slip faults and submarine landslides. However, research on the interaction between submarine telecommunication cables and lateral seabed movements is limited. There is no existing method for evaluating the cable safety when subjected to lateral seabed movements. This paper aims to carry out finite element (FE) analysis and physical modeling to investigate the responses of submarine telecommunication cables to lateral seabed movements. A FE model is developed and validated by full-scale physical test results. After validation of the FE model, a series of parametric studies is performed covering typical ranges of soil properties, cable burial depths, cable characteristics and seabed movement characteristics. The parametric study results are summarized in a dimensionless plot, followed by a regression analysis. A simple but effective formula is proposed to predict the maximum cable strains induced by lateral seabed movements. The dominant parameters that control submarine cable responses are identified and incorporated into the formula. Safety criteria for submarine telecommunication cables are also proposed for evaluating the cable safety when subjected to lateral seabed movements. [ABSTRACT FROM AUTHOR]