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• Thermo-elasto-plasticity model to predict the welding residual stress. • Norton creep model of X80 steel from the evaluated-temperature tests. • Quantitative evaluation of creep relaxation on residual stress relief by local post-weld heat treatment. The residual stress in girth-butt weld presents safety risks for large-diameter oil-gas pipelines, necessitating an in-depth investigation into the welding residual stress and the development of effective methods to mitigate these stresses, thereby enhancing structural integrity. In this work, a finite element girth-butt welding model was developed to predict the residual stress of X80 pipelines. The residual stress relief resulting from local post-weld heat treatment (PWHT) was simulated based on the Norton creep model applicable to X80 steel. The simulation results, encompassing the residual stress both before and after PWHT, were validated through blind-hole drilling measurements. The results demonstrate that the welding residual stresses across all orientations were significantly reduced following PWHT, with a maximum stress reduction of approximately 360 MPa. The primary mechanical mechanism for residual stress relief was identified as high-temperature creep, and it was concluded that the PWHT alleviated welding residual stress effectively when the heating temperature exceeded the creep activation temperature. The consistency between the finite element analysis results and the experimentally measured residual stresses affirms the validity and feasibility of the finite-element-based approach for predicting welding residual stresses. [ABSTRACT FROM AUTHOR]

• Thermo-elastic response of closed FG-GPLRC cylindrical shell with different thermal boundary conditions (TBCs) is studied. • Analytical solutions for radial and hoop stresses and radial displacement of the cylindrical shell are derived. • GPL distributions V and O are preferred patterns for FG-GPLRC cylindrical section and hemispherical ends respectively. • Closed FG-X-GPLRC cylindrical shell with higher GPL content has higher thermal conductivity hence higher thermal stresses. This paper investigates, for the first time, the thermo-elastic responses of a functionally graded (FG) graphene nanoplatelets (GPLs) reinforced composite (FG-GPLRC) closed cylindrical shell under a temperature field due to steady-state thermal conduction along thickness direction. A comprehensive thermo-elastic model covering various thermal boundary conditions (TBCs) is established. Analytical solutions for both radial stress and hoop stress of the shell are derived based on the plane hypothesis and displacement continuity conditions between the cylindrical shell and hemispherical ends. A parametric study is conducted to investigate the effects of GPL distribution pattern, weight fraction and geometry as well as TBCs on thermal stresses and deformation of the shell. It is found that GPL distributions V and O are preferred patterns for both FG-GPLRC cylindrical shell and hemispherical ends, respectively. The closed FG-X-GPLRC cylindrical shell with higher GPL concentration has higher thermal conductivity consequently higher thermal stresses. The research findings are of practical importance for the applications and design of closed FG-GPLRC shells in a variety of engineering sectors. [ABSTRACT FROM AUTHOR]

The failure of petroleum casings due to the combined effects of CO 2 /H 2 S corrosion and internal pressure has become a main concern during the exploitation of high-temperature, high-pressure, and high-corrosion gas fields. Therefore, establishing a corrosion evolution model is crucial for accurately predicting the service life of casings. In this study, an analytical model describing the corrosion rate of casing steel TP110TS under different CO 2 /H 2 S partial pressures and applied stresses was established, combined with the mechanical-chemical effect. The weightlessness method was used to determine the model parameters from the experimental results using a multiple regression. Based on the elasticity, a service life prediction model considering mechanical property attenuation and casing stress fluctuation was established from the assumption of uniform thickness thinning. The effects of internal pressure and CO 2 /H 2 S partial pressures on the service life were analyzed. The corrosion rate initially decreased with time. However, the stress increased as the wall thickness decreases from corrosion. The stress-promoting corrosion effect gradually manifested, and the corrosion rate rapidly increased. The higher the internal pressure and H 2 S/CO 2 partial pressure, the shorter was the service life of the casing. In the H 2 S/CO 2 coexistence environment, the influence of H 2 S partial pressure was more significant than that of CO 2. • The multi-factor corrosion model of TP110TS steel in H 2 S/CO 2 coexistence environment was established. • The H 2 S dominated the corrosion mechanism of TP110TS steel in the specific pressure ratio range in H 2 S/CO 2 coexistence. • The service life was predicted considering - dynamic stress attenuation and uniform thickness thinning from corrosion. [ABSTRACT FROM AUTHOR]

Reasonable condition adjustment of the auxiliary machinery can optimize the operation performance of the Combined Cycle Gas Turbine (CCGT) power station. In this paper an optimization method for the operation control of the auxiliary equipment based on deep learning is proposed and applied to an F-class gas turbine generation unit. A database of the optimal operating conditions is established to achieve the best economic benefit based on the analysis of two years of historical operation data. The control optimization models are built using the machine learning algorithms including the Multi-Layer Perceptron (MLP), Supporting Vector Machine (SVM), Gaussian process regression and linear regression methods and their accuracy has been compared. The input parameters of these models consist of the load rate, the heating output and the ambient temperature, with the output parameters including the electrical currents for the mechanical draft cooling tower, the high pressure feed pump, the medium pressure feed pump and the condensate pump. The MLP model is designed with different network hidden layer structures and provides the highest calculation accuracy with the least average error of 1.82 %. Different training data sizes are compared and the optimal control trajectory is analyzed. The result can provide useful references for the optimization of auxiliary equipment operations. • Achievement of CCGT auxiliary machinery control optimization models. • Establishment of the optimal operating condition database. • Determination of the best machine learning algorithm using the database. [ABSTRACT FROM AUTHOR]

• Sintering parameters on thermomechanical performance of the silver film were analyzed. • Anand constitutive model of sintered silver was constructed by the creep tests. • Electro-thermal–mechanical coupling analysis was conducted to obtain the cyclic creep behavior of the sintered silver solder. • Creep fatigue life prediction of the sintered silver solder from FEM analysis was verified by power on–off cycling tests. In this work, the creep samples of sintered silver were prepared by the chemical reduction method. According to the creep testing results, the Anand constitutive model was established to demonstrate the creep characteristics of sintered silver within a certain temperature range. According to the finite element electro-thermal–mechanical coupling analysis, the cyclic creep characteristics of sintered silver solder in the SiC-IGBT module under power cycling were simulated. The results shows that the sintering pressure and temperature can greatly promote the integrity of sintered silver by enhancing inert-particle bonding strength, and the established Anand model can effectively describe the creep behavior of sintered silver. The predicted results from electro-thermal–mechanical simulation were in good agreement with the power cycling testing results under the same condition. The finite element-based creep fatigue model is effective in predicting the creep fatigue life of sintered silver solders. [ABSTRACT FROM AUTHOR]

• The partial pressure ratio H 2 S/CO 2 dominated the corrosion process and corrosion mechanism of X80 in H 2 S/CO 2 coexistence. • The corrosion rate reaches its maximum near 100 °C in the simulated temperature range (50 °C–150 °C). • X80 steel has a higher stress corrosion cracking resistance under the H 2 S/CO 2 coexistence environment. In this work, the H 2 S / CO 2 coexistence environment was simulated in a high-temperature and high-pressure reactor. The influence of H 2 S/CO 2 partial pressure (0/1.2, 0.7/1.2 and 2.0/1.2 MPa), temperature (50, 100 and 150 °C) and applied stress (30%, 70% and 90% σ s) on the corrosion rates of natural gas pipeline steel X80 was investigated by the weight loss measurements combined with the SEM, EDS and XRD techniques. The results show that the corrosion of X80 steel under pure CO 2 condition is much more serious than that under H 2 S/CO 2 coexistence. The corrosion stability of amorphous film can be improved by the formation of amorphous Cr (OH) 3 in the presence of H 2 S, which provides better surface protection than in the pure CO 2 environment. The corrosion of X80 steel in H 2 S/CO 2 coexistence is dominated by H 2 S corrosion and the corrosion rates increase with the increase of H 2 S partial pressure. The corrosion rate firstly increases with the increase of temperature, and the highest corrosion rate occurs near 100 °C under the existing experimental conditions. After that, the corrosion rate began to decrease. The applied stress significantly affects the corrosion rate, and high stress speeds up the corrosion process of X80 steel in the H 2 S/CO 2 coexistence environment. [ABSTRACT FROM AUTHOR]

A series of C10 non-basic building block-substituted, levofloxacin core-based derivatives were synthesized in 43–86% yield. The antibacterial activity of these new fluoroquinolones was evaluated using a standard broth microdilution technique. The quinolone ( S )-9-fluoro-10-(4-hydroxypiperidin-1-yl)-3-methyl-7-oxo-3,7-dihydro-2 H -[1,4]oxazino[2,3,4- ij ]quinoline-6-carboxylic acid l -arginine tetrahydrate exhibited superior antibacterial activity against quinolone-susceptible and resistant strains compared with the clinically used fluoroquinolones ciprofloxacin, levofloxacin, moxifloxacin, penicillin, and vancomycin, especially to the methicillin-resistant Staphylococcus aureus clinical isolates, penicillin-resistant Streptococcus pneumoniae clinical isolates, and Streptococcus pyogenes . [ABSTRACT FROM AUTHOR]

Abstract: A series of 4-substituted 4-(1H-1,2,3-triazol-1-yl)piperidine building blocks was synthesized and introduced to the C7 position of the quinolone core, 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid, to afford the corresponding fluoroquinolones in 40–83% yield. The antibacterial activity of these new fluoroquinolones was evaluated using a standard broth microdilution technique. Among them, the quinolone 1-cyclopropyl-6-fluoro-7-(4-(4-formyl-1H-1,2,3-triazol-1-yl)piperidin-1-yl)-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid (34.15) exhibited comparable antibacterial activity against quinolone-susceptible and multidrug-resistant strains, especially to Staphylococcus aureus and Staphylococcus epidermidis, in comparison with ciprofloxacin and vancomycin. [Copyright &y& Elsevier]

Abstract: A series of non-basic building blocks was synthesized and introduced to the C7 position of the quinolone nucleus 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid to afford the corresponding fluoroquinolones in 46–85% yield. The antibacterial activity of these new fluoroquinolones was evaluated using a standard broth microdilution technique. The sulfur-containing quinolone, 7-(2-thia-5-azabicyclo[2.2.1]heptan-5-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid exhibited a superior antibacterial activity against quinolone-susceptible and multidrug-resistant strains in comparison with the clinically used fluoroquinolones ciprofloxacin and vancomycin, especially to the Streptococcus pneumonia and multidrug-resistant S. pneumonia clinical isolates. [Copyright &y& Elsevier]

Abstract: A new type of chiral tricarboxylate containing multiple stereocenters was synthesized via the one-pot reaction of a β-ketoester, (S)-phenylethylamine, and ethyl glyoxylate. High yields and diastereoselectivities (up to 96:4 dr) were obtained under optimal conditions. The reaction of the chiral tricarboxylate with Zn(BH4)2 gave chiral γ-lactones in good yields with up to 92:8 dr. The structures and configurations of the new chiral tricarboxylates were characterized by X-ray diffraction analysis. [Copyright &y& Elsevier]

In this work, a unified theoretical solution of plastic limit load for thin-walled pipeline with an incomplete welding defect is proposed by the Net Section Collapse (NSC) criteria. The plastic limit torque of the thin-walled pipeline with an incomplete circumferential welding defect is calculated by the sand pile analogy method. The unified theoretical solutions of plastic limit loads for the pressure pipeline with a circumferential welding defect under combined tension, torsion and bending moment are deduced, and the influences of circumferential length and defect position on the plastic limit loads are discussed. The comparison with the finite element (FE) results show that the theoretical plastic limit loads of the pressured circumferentially defective pipeline based on the extended NSC criteria are reliable. The study can provide an important theoretical basis to establish the safety evaluations towards the pressure pipelines with incomplete welding defects. • The limit torque of pipeline section with a circumferential welding defect was derived by the sand pile analogy method. • A unified theoretical solution of plastic limit load for thin-walled pipeline was deduced. • The limit loads of pipeline with a circumferential defect under all load combinations could be extended from this model. • This limit load based safety evaluation method is applicable for both volumetric and crack-like defective pipelines. [ABSTRACT FROM AUTHOR]

This paper presents the first attempt to investigate the fracture behavior of functionally graded multilayer nanocomposite strip reinforced with a low content of graphene platelets (GPLs) whose weight fraction is gradually changed in the thickness direction according to different non-uniform and uniform distribution patterns. Based on the transfer matrix method and Fourier integral transform technique, the governing equations of a multi-layered model of the GPL reinforced functionally graded strip are derived within the framework of elasticity theory which are then transformed to Cauchy singular integral equations. Both mode I and mode II stress intensity factors (SIFs) of a parallel interface crack embedded in a functionally graded GPL-reinforced composite (FG-GPLRC) strip are solved numerically by using the linear multi-layered (LML) fracture model. A detailed parametric study is carried out to investigate the effects of the distribution pattern, weight fraction, geometry and size of GPL nanofillers as well as crack location on the fracture behaviors of the FG-GPLRC strip. • Fracture behavior of functionally graded multilayer graphene nanoplatelets reinforced composite strips is investigated. • Analytical solutions are presented for Mode-I and Mode-II SIFs. • The effect of GPL weight fraction to the SIFs is highly dependent on the GPL distribution pattern. • The effect of GPL geometry and dimension on the SIFs is found to be relatively limited. • GPL distribution pattern has an important influence on the SIFs with pattern X. [ABSTRACT FROM AUTHOR]

A hierarchically porous β-tricalcium phosphate (β-TCP) bioceramic scaffold was prepared by in situ foaming using the sol-gel method, and a nonionic surfactant Pluronic F127 (EO 99 PO 65 EO 99) was used as the template. The average size of the connecting macropores in the scaffolds increases in the range of 200–500 μm as the amount of the surfactant F127 decreases. The size of micropores on the scaffold wall is between 0.5 and 5 μm, and the microporosity reduces with an increase in the sintering temperature. In addition, the morphology of grains is rough and contains 3-10-nm nanopores and nanoscale "groove" pores due to the removal of F127 as a "soft templating" material. Finally, immersion experiments with simulated body fluids (SBF) in vitro showed that the scaffold had good bioactivity. The hierarchically porous β-TCP bioceramic prepared by this method has the advantages of low cost and a simple process; thus, this material is ideal for repairing bone defects in orthopaedics. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) possesses excellent bioactivity/osteointegration properties. Nevertheless, its inferior flexural strength and fracture toughness limit its use in human weight-bearing parts. We investigated a microwave sintering technology which can be effectively used to develop titanium dioxide-hydroxyapatite (TiO 2 -HAP) ceramics with different amounts of TiO 2 (0.8,1.6,2.4,3.2,4.0,4.8,5.6 and 6.4 wt%), which contribute to extremely high flexural strength (90–130 MPa) along with a good combination of elastic modulus and fracture toughness. The results of the Rietveld refinement show that multiphase bioceramics (HAP, β-TCP) can be achieved by doping nano-TiO 2 under microwave sintering. Despite the fact that the main phases of the sintered TiO 2 -HAP ceramics are HAP and β-TCP, X-ray diffraction confirms the formation of the CaTiO 3 and CaTi 2 O 4 (OH) 2 phases. Furthermore, the sintering reactions to form these phases are discussed and the results show that an appropriate amount of nano-TiO 2 can not only effectively inhibit the growth of grain, but also change the fracture mode and increase the relative density. Finally, it is found that doping nano-TiO 2 by microwave heating is an effective technique for producing HAP/β-TCP composite load-bearing implants in clinical applications without coarsening the size of grain. [ABSTRACT FROM AUTHOR]

Offshore drilling is facing a series of difficulties in deepwater and ultra-deepwater environments, such as harsh operating environments and complex downhole geological conditions. How to achieve full management of the wellbore pressure during deepwater drilling has become one of the main concerns. The dual gradient drilling technology realizes wellbore pressure management by applying multiple pressure gradients in the annulus. It also enables the managed pressure drilling technology, such as constant bottomhole pressure drilling and mud cap drilling, to be applicable for deepwater conditions. However, the decision-making of deepwater dual gradient drilling scheme is always affected by many factors, which brings confusion for scheme optimization of deepwater drilling. In this work, according to the characteristics of four typical dual gradient drilling technologies, the fuzzy comprehensive evaluation method is applied to determine the most effective one from the aspects of drilling capacities and equipment requirements in a particular scenario. The fuzzy comprehensive evaluation results show that the subsea mud lifting pump system has better applicability in this case. • The technique features of four mainstream DGDs are discussed according to the deepwater drilling requirement. • The FCE system is built to evaluate the comprehensive score of each DGD technology. • MLP is the most optimal DGD scheme in the application scenario provided in this work. [ABSTRACT FROM AUTHOR]

Nd-doped YAG transparent ceramics were prepared by microwave sintering. In this paper, the green bodies from high-purity commercial powders were sintered from 900 °C to 1750 °C for different lengths of time (0.5–2 h) by microwave heating. By optimizing the microwave heating parameters (the heating rate at different stages of microwave sintering, sintering temperature and holding time), the microstructures and optical properties of transparent ceramics can be effectively improved. The phase transformation, densification process and optical properties of Nd:YAG transparent ceramics were discussed. The liquid phases strongly absorb microwave radiation and affect the sintering results of samples during microwave sintering. The highest in-line transmittances of Nd:YAG transparent ceramic fabricated at 1750 °C for 2 h were 76.5% at 400 nm and 80.6% at 1064 nm. The fluorescence emission spectra and lifetime depending on different heating conditions were also discussed. [ABSTRACT FROM AUTHOR]