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A study of porous YSZ abradable sealing coating (ASC) plasma-sprayed onto SiC f /SiC ceramic matrix composites (CMC) through the compatibility of intermediate layers is reported. The multilayer Si/Yb 2 Si 2 O 7 /LaMgAl 11 O 19 thermal-environmental barrier coating (T-EBC) is served as intermediate layers in consideration of its ability to protect the CMC from recession and ease the misfit of the thermal expansivity. Isothermal exposure and thermal shock tests were conducted at 1200°C and led to the decomposition of t'-ZrO 2 phase to t-ZrO 2 and c-ZrO 2 phases in YSZ topcoat, the formation of mud-cracks throughout the entire coating structure and thermally grown oxide (SiO 2), with following an Yb 2 Si 2 O 7 reaction layer. The measured bond strength of the coated samples was 5.47 ± 0.85 MPa, and the fracture position mainly happened inside the CMC substrate. The Superficial Rockwell Hardness (HR15Y) considered to be an important factor in abradability increased by only 1.34% after 1200°C isothermal exposure for 100 h, showing excellent high temperature hardness stability. The abradability of the ASC was investigated by a sliding wear test, the fatigue wear mainly occurred in worn scar when encountering Si 3 N 4 ceramic ball with high hardness and low thermal conductivity, while adhesive wear occurred when GCr15 steel ball with low hardness and high thermal conductivity are encountered. [ABSTRACT FROM AUTHOR]

In addition to seismic waves, coseismic displacement is also generated during earthquake events, which decreases gradually away from the seismogenic fault and may bring damages to tunnels in the area. This study aims to investigate the nonlinear response of tunnels under coseismic displacement induced by strike-slip fault. First, a method for applying coseismic displacement on the finite-element model (FEM) is developed by converting the displacement into equivalent nodal forces applied on the element nodes. Then, the nonlinear response of the tunnel under coseismic displacement is numerically investigated, considering the influence of the angle of the tunnel axis with respect to the fault trace, the epicentral distance, and the earthquake magnitude. The numerical results show that the tunnel might suffers tensile damages under coseismic displacement induced by the strike-slip fault, which indicates the coseismic displacement, as one kind of earthquake loads, should also be considered in seismic analysis for tunnels. Moreover, some other conclusions can be drawn: (1) The tensile deformation of the tunnel increases first and then decreases, as the tunnel axis changes from being perpendicular to the fault trace to being parallel to the fault trace, which is converse for the shear deformation; (2) the damage degree on the tunnel lining increases first and then decreases while the epicentral distance increases; (3) with an increasing earthquake magnitude, the tunnel damage increases dramatically. This study offers an insight into further research on tunnel response under coseismic displacement. [ABSTRACT FROM AUTHOR]

In this work, Co-based metal-organic framework (ZIF-67) coupled polyimide (ZIF-67/PI) film was fastly and effectively transformed into flexible Co nanoparticles modified 3D N-doped porous carbon (Co@3D NPC) electrode device using simple laser ablation technique at room temperature. Compared with 3D NPC electrode device that derived from pure polyimide film, Co@3D NPC exhibited significantly enhanced electron transfer ability, physical adsorption ability and electrochemically active surface area. By adjusting the laser power and ZIF-67 concentration, the surface morphology and electrochemical property of the Co@3D NPC electrode devices can be easily controlled. Furthermore, the fabricated flexible Co@/3D NPC electrode device exhibited exceptional electrochemical activity for the sensitive detection of clozapine and albendazole, two kinds of common veterinary drug and pesticide. The detection sensitivity of Co@/3D NPC electrode device reached to 410.47 μA μM−1 cm−2 and 580.33 μA μM−1 cm−2, with detection limits as low as 2.8 nM and 2.5 nM for clozapine and albendazole, respectively. Besides, the Co@/3D NPC electrode device demonstrated excellent stability and accuracy. Given the advantages of laser ablation technology, including its low cost, scalability, and high stability, the reported Co@/3D NPC electrode device holds significant potential for practical applications in the field of electrochemical analysis. [Display omitted] • Disposable Co@3D NPC electrode devices were facilely prepared at room temperature. • Co@3D NPC exhibited greatly enhanced electron transfer and physical adsorption ability. • Robust electrochemical sensing platform for the detection of clozapine and albendazole. • Simple strategy for guiding and synthesizing other novel electrode devices. [ABSTRACT FROM AUTHOR]

Phase composition, microstructure and mechanical properties of ytterbium disilicate (Yb 2 Si 2 O 7 , YbDS) coatings fabricated via atmospheric plasma spray (APS) at different deposition temperatures were studied. Two layers with distinct pore distributions were observed in the YbDS top coat, the formation of pores correlated fairly well with the thermal gradients of splats after the droplets impinged on the substrate or deposited splats. Microstructure evolution with the thicknesses of YbDS top coat resulted from splat stacking and temperature accumulation. In addition, the significant crystallinity improvement and cracks reduction of YbDS top coat arose with the increased deposition temperature. X-ray diffraction patterns indicated that the metastable ytterbium monosilicate (Yb 2 SiO 5 , YbMS) appeared in YbDS coatings and they disappeared after thermal-treatment due to the phase transformation. The mechanical properties of the YbDS coatings were affected notably by the phase composition and microstructure. [ABSTRACT FROM AUTHOR]

Analytical solutions are widely adopted in the preliminary seismic design of tunnels, which gives credit to their quick response and convenience to provide the internal forces and displacements of tunnels. In the first part of this paper, five analytical solutions are extensively verified by comparing them with the reference solution which obtained by the dynamic finite element method. Some suggestions are given for their application in design according to the prediction results. The analytical solutions contain some assumptions, which may not be applicable to all possible scenarios. Therefore, the application scope of analytical solution in practical engineering is limited, and this application scope has not been discussed at present. In the second part of this paper, the applicability evaluation index is established for the first time to evaluate the critical condition for the application of analytical solution. Then, the applicability function is obtained by fitting the relationships between the critical condition and the flexibility ratios, which can be convenient to calculate the critical condition for the application of analytical solutions in engineering. Finally, the applicability of analytical solution in some engineering projects is correctly evaluated based on the proposed applicability evaluation index and applicability function. • The results of dynamic finite element analysis are used as reference solutions to verify the five analytical solution. • Applicability evaluation index is proposed to evaluate the critical condition for the application of analytical solution. • Applicability function is obtained by fitting the relationships between the critical condition and the flexibility ratios. • The applicability of analytical solution in some engineering projects is correctly evaluated. [ABSTRACT FROM AUTHOR]

Analytical solutions can quickly and simply evaluate stresses and displacements in tunnels and are widely adopted in the preliminary design phase of tunnels. Tunnels must be able to withstand static loading and seismic loading. This paper proposes new analytical solutions for the stresses and displacements of tunnels under static and seismic loading. The tunnel lining is treated as a thick-walled cylinder. Moreover, the contact stiffness coefficient k 0 and the stress release coefficient η 0 are introduced to consider the arbitrary contact conditions at the ground–lining interface and the amount of excavation unloading. The new analytical solutions are verified by comparison with finite element analysis results. The results demonstrate the accuracy and applicability of the proposed analytical solutions. In addition, parametric analyses are conducted to explore the effects of the stress release coefficient η 0 and stiffness coefficient k 0 at the ground–lining interface, as well as the incident angle α of shear waves. The analysis results indicate that the proposed analytical solutions offer satisfactory performance and can be applied as an effective tool for preliminary tunnel design. [ABSTRACT FROM AUTHOR]

The objective of this work is to design environmental barrier coatings with new structure to improve the thermal shock and oxidation resistance. A novel tri-layer SiC nanowires+Si/Yb 2 Si 2 O 7 -Si/Yb 2 Si 2 O 7 coating was designed and fabricated on the surface of C/SiC composites by chemical vapor reaction route and combination of the method of atmospheric plasma spraying. All coated samples were subjected to thermal shock test at 1300 ℃. Results indicated that the interfacial bond among the layers in the coating system and C/SiC composites was still intact without delamination crack. The Si in the Yb 2 Si 2 O 7 -Si layer consumed the oxygen diffused into coating and then reacted with Yb 2 SiO 5 to form Yb 2 Si 2 O 7 , which could decrease the release of tensile stress caused by thermal mismatch. The study also investigates the Yb 2 Si 2 O 7 formation in the Yb 2 SiO 5 -Si system, and finds that the Yb 2 Si 2 O 7 formation was controlled by the diffusion of Yb3+ and Si4+ ions through the Yb 2 Si 2 O 7 layer. [ABSTRACT FROM AUTHOR]

Seismic stability of slopes has been traditionally analyzed with vertically propagated earthquake waves. However, for rock slopes, the earthquake waves might approach the outcrop still with a evidently oblique direction. To investigate the impact of obliquely incident earthquake excitations, the input method for SV and P waves with arbitrary incident angles is conducted, respectively, by adopting the equivalent nodal force method together with a viscous-spring boundary. Then, the input method is introduced within the framework of ABAQUS software and verified by a numerical example. Both SV and P waves input are considered herein for a 2D jointed rock slope. For the jointed rock mass, the jointed material model in ABAQUS software is employed to simulate its behavior as a continuum. Results of the study show that the earthquake incident angles have significance on the seismic stability of jointed rock slopes. The larger the incident angle, the greater the risk of slope instability. Furthermore, the stability of the jointed rock slopes also is affected by wave types of earthquakes heavily. P waves induce weaker responses and SV waves are shown to be more critical. [ABSTRACT FROM AUTHOR]

The strength and deformation characteristics of rocks are the most important mechanical properties for rock engineering constructions. A new nonlinear strength criterion is developed for rocks by combining the Hoek-Brown (HB) criterion and the nonlinear unified strength criterion (NUSC). The proposed criterion takes account of the intermediate principal stress effect against HB criterion, as well as being nonlinear in the meridian plane against NUSC. Only three parameters are required to be determined by experiments, including the two HB parameters σc and mi. The failure surface of the proposed criterion is continuous, smooth and convex. The proposed criterion fits the true triaxial test data well and performs better than the other three existing criteria. Then, by introducing the Geological Strength Index, the proposed criterion is extended to rock masses and predicts the test data well. Finally, based on the proposed criterion, a triaxial elasto-plastic damage model for intact rock is developed. The plastic part is based on the effective stress, whose yield function is developed by the proposed criterion. For the damage part, the evolution function is assumed to have an exponential form. The performance of the constitutive model shows good agreement with the results of experimental tests. [ABSTRACT FROM AUTHOR]

The faults play an important role in inducing tremendous potential threat to the stability capability of embedded tunnels in strong earthquake events. Based on the finite element method with the viscous-spring artificial boundary, the earthquake motions of oblique incidence can be transformed into the equivalent nodal forces acting on the truncated boundary of finite element model. In the present work, the formulas of equivalent nodal forces for the 2-D plane P waves with arbitrary incident angles are deduced and implemented into the commercial software ABAQUS. The accuracy of the formulas and the implementation are demonstrated by the numerical examples of a 2-D semi-infinite space and an circular lined tunnel in half-space subjected to obliquely incident P waves. The proposed numerical method is employed to investigate the non-linear responses of the tunnels within surface normal fault ground under obliquely incident P waves. The numerical results indicate that the tunnels buried in the hanging wall, in the foot wall and across the fault, suffer different failure patterns. The tunnels across the fault suffer the most serious plastic damage, followed by that within the hanging wall. Moreover, the seismic responses of the tunnels across the fault and within the hanging wall increase with the inclination degree of the incident P waves, as well as opposite relationship for tunnels within the foot wall. [ABSTRACT FROM AUTHOR]

The high concentration of fluoride and phosphate in phosphogypsum leachate is harmful to the environment and ecosystem. Thus, there is a need to develop feasible materials or technologies to remove both fluoride and phosphate in acidic phosphogypsum leachate. In this study, sulfoaluminate cement (SC) was used to simultaneously remove fluoride and phosphate in wastewater based on its moderate alkalinity and rich content of metal elements (Ca, Al and Fe, etc). The acidized sulfoaluminate cement (ASC) composite was prepared through modifying SC with hydrochloric acid, which can increase the specific surface areas of the raw SC, as well as the activity of the metal elements in SC. Compared with other coagulants, ASC showed excellent removal performance for fluoride and phosphate, such as higher removal efficiency, better effluent quality, and accelerated settling rate. The fluoride and phosphate removal performances of ASC herein were investigated at different dosages, pH values, coexisting substances, and initial concentrations. As a result, ASC exhibited wide pH adaptability and satisfactory selectivity for fluoride and phosphate. The possible removal mechanisms of fluoride and phosphate by ASC included chemisorption, ion exchange, and precipitation. The main end products associated with fluoride were fluorite (CaF 2), aluminum fluoride (AlF 3), and iron trifluoride (FeF 3). The main final products amid phosphate removal, on the other hand, were brushite (CaHPO 4 ·2H 2 O), aluminophosphate ((H 3 O)·AlP 2 O 6 (OH) 2), silicocarnotite (Ca 2 SiO 4 ·Ca 3 (PO 4) 2) and iron phosphate (Fe(H 2 PO 4) 3). More importantly, ASC can effectively treat the phosphogypsum leachate at a wide range of concentrations, and the concentrations of phosphate and fluoride in the effluents were lower than 0.5 mg P L−1 and 4 mg L−1, respectively. To sum up, ASC is a competitive candidate to treat wastewater with high fluoride and phosphate content, such as phosphogypsum leachate. [Display omitted] • Hydrochloric acid treatment increased the metal ion activity in sulfoaluminate cement (SC). • Phosphate removal efficiency was maintained at about 99% in wide pH range. • ASC was able to simultaneously and efficiently remove fluoride and phosphate from phosphogypsum leachate. • The removal mechanism of fluoride and phosphate by ASC included chemisorption, ion exchange, and precipitation. [ABSTRACT FROM AUTHOR]

Active faults pose significant threats to the structural integrity of mountain tunnels in seismic active zones. Post-earthquake reconnaissance revealed that numerous tunnels were damaged during past earthquakes, specifically those crossing active fault zones. In this study, the structural response and damage mechanism of a water conveyance tunnel subjected to reverse faulting was investigated. A three-dimensional finite element model incorporating the cohesive interface elements was developed to simulate the nonlinear process of the reverse fault rupture. The ground deformation and tunnel damage characteristics predicted by the numerical analysis were in good agreement with the field observations and experimental results, which proved the feasibility of the proposed simulation scheme. Moreover, a parametric study was conducted to estimate the effects of dip angle, surrounding rock property, tunnel rigidity, and friction coefficient between linings on tunnel performance. The results showed that the damage zone with softer rock masses of grade IV to V, based on the Chinese Guidelines for Design of Highway Tunnel, generally led to moderate structural damage to the tunnel. The tunnel's performance in the damage zone can be further enhanced by increasing tunnel rigidity and smoothness of the external surface of the secondary lining. [ABSTRACT FROM AUTHOR]

Abstract: Based on anecdotal evidence of anti-hypertensive effect of Gold Nine Soft Capsules, an in vivo study of this complex Chinese “herbal-based” medicine was initiated. Dosage of the content of Gold Nine capsules in spontaneous hypertensive rats showed a remarkably good effect. This led to further investigation of the components of the preparation and eventual identification of three known anti-hypertensive drugs; amlodipine, indapamide and valsartan, which were not declared on the label. Compounds were rapidly identified using LC–HRMS and LC–MS–SPE/NMR, quantified by HPLC, and the in vivo activity of a combination of commercially purchased standards was shown to be equivalent to that of the capsule content. Adulteration of herbal remedies and dietary supplements with synthetic drugs is an increasing problem that may lead to serious adverse effects. LC–MS–SPE/NMR as a method for the rapid identification of such adulterants is highlighted in this case study. [Copyright &y& Elsevier]

Simplified analytical solutions are very useful tools for the seismic preliminary design of tunnels and can quickly and easily give seismic responses to structures. This study presents simplified analytical solutions for the stress and deformation of circular composite-lined tunnels subjected to in-plane S-waves. Unlike previous solutions for single-lined tunnels, the proposed analytical solutions are suitable for tunnels with arbitrary numbers of linings. Moreover, tunnel linings are treated as multilayer thick-walled cylinders in the new solutions. Compared with thin shell or beam models used in previous analytical solutions, thick-walled cylinders provide more precise forecasts. In addition, the slippage effect at the lining-lining and ground-lining interface is considered by introducing a spring-type flexibility coefficient into the interaction force–displacement relationship. To verify the proposed analytical solutions, dynamic numerical examples are studied. The proposed solutions have good agreement with the dynamic numerical results and outperform previous analytical solutions. Finally, parameter studies are conducted to investigate the effect of the flexibility coefficient, degraded zone around the outermost lining and steel plate supporting the innermost lining on the seismically induced stresses and deformations. The proposed analytical solutions are applicable for approximately evaluating the seismic responses of circular tunnels with composite linings. [ABSTRACT FROM AUTHOR]

The integrity of lens epithelial cells (LECs) lays the foundation for lens function and transparency. By contrast, epithelial-mesenchymal transition (EMT) of LECs leads to lens fibrosis, such as anterior subcapsular cataracts (ASC) and fibrotic forms of posterior capsule opacification (PCO). However, the underlying mechanisms remain unclear. Here, we aimed to explore the role of long non-coding RNA (lncRNA) H19 in regulating TGF-β2-induced EMT during lens fibrosis, revealing a novel lncRNA-based regulatory mechanism. In this work, we identified that lncRNA H19 was highly expressed in LECs, but downregulated by exposure to TGF-β2. In both human lens epithelial explants and SRA01/04 cells, knockdown of H19 aggravated TGF-β2-induced EMT, while overexpressing H19 partially reversed EMT and restored lens epithelial phenotypes. Semi-in vivo whole lens culture and H19 knockout mice demonstrated the indispensable role of H19 in sustaining lens clarity through maintaining LEC features. Bioinformatic analyses further implied a potential H19-centered regulatory mechanism via Smad-dependent pathways, confirmed by in vitro experiments. In conclusion, we uncovered a novel role of H19 in inhibiting TGF-β2-induced EMT of the lens by suppressing Smad-dependent signaling, providing potential therapeutic targets for treating lens fibrosis. [ABSTRACT FROM AUTHOR]

Deep neural networks (DNNs) have facilitated the development of computer-aided diagnosis (CAD) systems for fundus diseases, helping ophthalmologists to reduce missed diagnoses and misdiagnosis rates. However, the majority of CAD systems are data-driven, but lack the prior medical knowledge that can be performance-friendly. In this regard, we innovatively proposed a human-in-the-loop (HITL) CAD system by leveraging ophthalmologists' eye-tracking information. Concretely, the HITL CAD system was implemented on the multi-instance learning (MIL), where clinicians' gaze maps were beneficial to cherry-pick diagnosis-related instances. Furthermore, the dual-cross-attention MIL (DCAMIL) network was utilized to curb the adverse effects of noisy instances. Meanwhile, both the sequence augmentation (SA) module and the domain adversarial network (DAN) were introduced to enrich and standardize the instances in the training bag, respectively, thereby enhancing the robustness of our method. We conduct comparative experiments on our newly-constructed datasets (namely, AMD-Gaze and DR-Gaze) for the AMD and early DR detection, respectively. Rigorous experiments demonstrate the feasibility of our HITL CAD system and the superiority of the proposed DCAMIL, which fully exploits ophthalmologists' eye-tracking information. These investigations indicate that clinicians' gaze maps, as prior medical knowledge, is potential to contribute to the CAD systems of clinical diseases. • We propose an eye-tracking-based HITL CAD system for fundus disease detection. • We propose a novel DCAMIL model with the contrast learning regularization. • We introduce the SA and DAN modules into the DCAMIL model. • We construct DR-Gaze and AMD-Gaze datasets according to clinical settings. [ABSTRACT FROM AUTHOR]

In this study, the garnet-type Yb 3 Al 5 O 12 coating was fabricated by atmospheric plasma spraying and its properties were systematically investigated. Results show the as-sprayed coating consists of crystalline Yb 3 Al 5 O 12 with amorphous phase, recrystallization occurs at 918.5 °C accompanied by a 0.32% volume shrinkage. Yb 3 Al 5 O 12 coating demonstrates low thermal conductivity (2.1 W/(m∙K) at 1000 °C) coupled with a moderate thermal expansion coefficient (8.87 × 10−6 K−1 from 200 °C to 1400 °C). Additionally, Yb 3 Al 5 O 12 coating displays remarkable structure stability and sintering resistance at elevated temperatures. Its robust corrosion resistance can be demonstrated by rapidly generating dense anorthite layers during CMAS corrosion and the lack of a discernible corrosion layer in water vapor corrosion. Yb 3 Al 5 O 12 /YSZ TBC undertakes a thermal cycling lifetime of 970 cycles, superior to YSZ of 764 cycles. This improvement is primarily ascribed to lower oxygen permeability of garnet layer. These preliminary results indicate that Yb 3 Al 5 O 12 coating might be suitable for advanced TBC applications. [ABSTRACT FROM AUTHOR]

A simplified analytical solution is developed for estimating the thrusts and bending moments of the circular tunnel in half space under the obliquely incident SV wave. The seismic waves impinging on the tunnel is obtained according to the elastic wave motion theory in half space firstly, which is the superposition of the incident and reflected SV waves and reflected P wave. Then, by considering the tunnel lining as a thick-wall cylinder, analytical solutions for internal forces of circular tunnel due to the incident and reflected SV waves and the reflected P wave are deduced, which enables more precise forecasts than previous analytical solutions by the thin shell model. The total tunnel internal forces are obtained finally through the superposition of the above solutions under three kinds of waves. The accuracy of the proposed analytical solution is verified by comparing with the dynamic numerical results. Moreover, the discussion about the effect of critical factors on the accuracy of the proposed analytical solutions is conducted, including the tunnel structure inertia, the seismic wavelength, the lining thickness and the tunnel depth. These results demonstrate that the proposed analytical solution performs well and can be adopted to predict the internal forces of circular tunnel under obliquely incident SV wave in seismic design. • Analytical solutions for circular tunnel in full space under SV and P waves are developed. • Analytical solution for circular tunnel in half space under obliquely incident SV wave is developed. • The present solutions are verified by comparing with dynamic numerical results. • Discussion about the effect of critical factors on the accuracy of the proposed analytical solutions is conducted. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 (LMA) with magnetoplumbite structure has emerged as a promising candidate for thermal barrier coating (TBC). However, the inherent high thermal conductivity and relatively low thermal expansion coefficient (TEC) of LMA impose limitations on its further application. In this work, a novel high-entropy hexaluminate (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 (HE-LMA) has been designed and prepared to overcome these obstacles. HE-LMA with homogeneous chemical composition distribution possesses excellent phase stability up to 1600°C. Moreover, the TEC of HE-LMA (9.22 × 10−6 K−1 at 1300°C) is larger than that of LMA. The high-entropy strategy effectively decreases the thermal conductivity of HE-LMA (from 3.27 W/(m⋅K) at room temperature to 2.19 W/(m∙K) at 1000°C) in comparison to that of LMA (3.63–2.62 W/(m∙K)). Furthermore, HE-LMA demonstrates higher microhardness and fracture toughness due to the lattice distortion. These results indicate that (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 has the potential to be applied as a TBC. [ABSTRACT FROM AUTHOR]

• A 3-D obliquely incident method for P waves was developed. • Nonlinear seismic response of a tunnel under 40 artificial accelerograms with different incident angles is analyzed. • PGV has incremental effect on the seismic response of tunnels under earthquake P waves with large incident angles. • PGA intends to increase the response of tunnels subjected to earthquake P waves with small incident angles. • PGD has little effect on the seismic response of tunnels. The response mechanism of tunnels under earthquake loads is a critical issue in tunnels located in seismically active regions. This study aims to investigate the seismic response and damage sensitivity of tunnels under earthquake motions with different peak ground acceleration, velocity and displacement (PGA, PGV and PGD). Based on the design acceleration response spectrum (ARS), four groups of total 40 artificial accelerograms are synthesized with specified PGA, PGV and PGD. In addition, for considering the wave travelling effect on the tunnel axial response, an obliquely incident method for P waves is developed by using the equivalent nodal force method. Then, the nonlinear response of tunnels subjected to artificial accelerograms with different incident angles are simulated, respectively. The numerical results indicate that the PGV and PGA have accretion effect on the seismic response of the tunnel. However, the impact of PGD on the tunnel earthquake response is less evident. The PGV has obvious incremental effect on the dynamic response of tunnels subjected to earthquake P waves with large incident angles. Compared with PGV, the PGA intends to increase the response of tunnels significantly under P waves with small incident angles. Thus, it is important to take the PGA and PGV into account during seismic analysis and design for tunnels. [ABSTRACT FROM AUTHOR]

Evaluating the impact of the isolation layer on the tunnel's response is crucial in the practical engineering. An analytical solution for the longitudinal seismic response of a tunnel covered by an isolation layer is first proposed in this study based on an improved elastic foundation beam model. Wherein, an equivalent beam model for the tunnel-isolation layer system is built. The tangential interaction effect at the ground-isolation layer-tunnel interfaces is taken into account by solving the ground-isolation layer-tunnel model under out-of-plane shearing stress. The proposed solution is verified by comparison with dynamic numerical results. Finally, the proposed analytical solutions are employed to investigate the seismic mitigation effects of the isolation layer on the longitudinal response of the tunnel, as well as the influence of the elastic modulus, thickness and Poisson's ratio of the isolation layer. The results indicate that the isolation layer can significantly reduce the longitudinal shearing force of the tunnel but always amplifies the longitudinal bending moment in most cases. Moreover, the mitigating effect of the isolation layer on the longitudinal response of the tunnel is sensitive to the elastic modulus and thickness, except for Poisson's ratio of the isolation layer. • An equivalent beam model for the tunnel-isolation layer system is built. • Tangential interactions at the ground-isolation-tunnel interfaces are considered. • Analytical solution of response for tunnel with isolation layer is proposed. • Seismic mitigation effects of the isolation layer are investigated. [ABSTRACT FROM AUTHOR]

An analytical solution for the seismic-induced thrust and moment of the circular tunnel in half-space under obliquely incident P waves is developed in this study, which is the superposition of the solution for deep tunnels under incident and reflected P waves and the reflected SV waves. To consider tangential contact stiffness at the ground-tunnel interface, a spring-type stiffness coefficient is introduced into the force-displacement relationship. Moreover, the tunnel lining is treated as the thick-wall cylinder, providing more precise forecasts than beam or shell models used in previous analytical solution, especially for tunnels with thick lining. The reliability of the proposed analytical solution is assessed by comparing with the dynamic numerical results. Based on the proposed analytical solution, parametrical studies are conducted to investigate the effect of some critical factors on the tunnel's seismic response, including the incident angles, the tangential contact stiffness at the ground-tunnel interface, and the relative stiffness between the ground and the tunnel. The results demonstrate that the proposed analytical solution performs well and can be adopted to predict the internal forces of circular tunnels under obliquely incident P waves in seismic design. [ABSTRACT FROM AUTHOR]

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La 2 (Zr 0.7 Ce 0.3) 2 O 7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D 0 →7F 2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D 0 →7F 2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D 0 →7F 2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials. [ABSTRACT FROM AUTHOR]

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La 2 (Zr 0.7 Ce 0.3) 2 O 7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D 0 →7F 2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D 0 →7F 2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D 0 →7F 2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials. [ABSTRACT FROM AUTHOR]

The composite bucket foundation of offshore wind turbines is subjected to a variety of loads in the marine environment, such as horizontal load H, vertical load V , bending moment M, and torque T. In addition, due to the characteristics of its connection section, the water flow around the foundation will produce scour pits of various degrees, reducing the depth of the bucket foundation, which has a nonnegligible impact on the overall stability of the bucket foundation. In this paper, the failure envelope characteristics of different combinations of loads on bucket foundations, including V -H-T, V -M-T, conventional V -H-M, and noncoplanar V -H-M, are numerically investigated with considering different scour depths. The numerical results indicate that the V -H-T, V -M-T, conventional V -H-M, and noncongruent V -H-M failure envelopes gradually shrink inwards with increasing scour depth, and the stability of the composite bucket foundation decreases; the conventional V -H-M failure envelope shows an asymmetry of convexity to the right, and the noncongruent V -H-M failure envelope shows an asymmetry of outward convexity to the left and right. The corresponding mathematical expressions for the failure envelope are obtained through the normalized fitting process, which can be used to evaluate the stability of the bucket foundation based on the relative relationship between the failure envelope and the actual load conditions, which can provide practical guidance for engineering design. [ABSTRACT FROM AUTHOR]

The study aims to investigate the influence of infrared emissivity on thermal barrier coating (TBCs) for service applications. Two double-layer TBCs, namely RMgAl 11 O 19 /YSZ (marked as RMA/YSZ, R=La, Pr) and conventional single-layer YSZ TBCs, were comparatively tested using a burner rig facility. The microstructure, infrared emissivity, and thermal cycling performance of the three TBCs were investigated. The results demonstrate that the emissivity of PrMA/YSZ has been improved by approximately 20% compared to LaMA/YSZ in the wavelength range of 2–6 µm, owing to an improvement in electronic transition. Due to higher emissivity, the surface temperature of PrMA/YSZ decreased by 70 °C under the same heat flux, leading to a reduction in coating aging and substrate temperature. Accordingly, PrMA/YSZ exhibited the highest thermal cycling lifetime among the three coatings. [ABSTRACT FROM AUTHOR]

The fault zone plays a vital role in the internal force responses of the tunnel. An analytical solution of the tunnel under the fault zone creeping is developed by taking account of normal and tangential interaction between the ground and tunnel. First, the elastic foundation beam model is used. Wherein, the normal interaction is considered by applying the displacements of the free field on the distal end of normal foundation springs. And the tangential interaction is transformed into bending moment applied on the beam. The analytical solution of the tunnel's response is gotten based on the model. Secondly, the numerical solutions from finite element model of 3D are provided to verify the validity of the proposed analytical solutions. Finally, the effect of the fault zone width, the elastic modulus of the fault and the concrete's grade of the lining are investigated. The results show that with the width of the fault zone increasing, the internal force decrease. The concrete's grade of the lining has opposite effects on the internal force of the tunnel. And with the growth of the elasticity modulus of the fault zone, the shear force and bending moment increase and decrease, respectively. • An analytical solution considering the tangential interaction at the ground-tunnel interface is developed. • The proposed analytical solution is verified by the numerical result obtained from the finite element model of 3D. • Effects of fault zone width, elasticity modulus of fault zone and concrete's grade of the lining are discussed. [ABSTRACT FROM AUTHOR]

The incident direction plays an important role in the seismic response of long lined tunnels. A simplified analytical solution is developed for estimating the seismic response of the circular tunnel under obliquely incident shear waves, including the principle stress and the internal forces and deformations on the cross section and longitudinal of the tunnel. Based on the elastic wave theory, the oblique incident shear wave can be decomposed into an axially propagating shear wave and a shear wave propagating transversely to the tunnel axis. A modified elastic foundation beam model is used to calculate the tunnel longitudinal response, which is based on Timoshenko beams resting on Winkler foundations with considering different tangential contact conditions. Furthermore, by adopting wave theory and Fourier transform, longitudinal response of tunnels under arbitrary seismic load can be obtained. Moreover, the flattening effect and out-plane response of tunnel cross-section caused by longitudinal bending are considered. The proposed analytical solution is verified by comparing with the dynamic numerical results. The effect of the incident angle, ground condition and contact condition on the seismic response of long lined tunnel is investigated by the simplified analytical solution. It is demonstrated that the proposed solution can be adopted to predict internal forces and deformations of circular tunnels under obliquely incident shear wave in preliminary design. • A simplified analytical solution is developed for estimating the seismic response of the circular tunnel under obliquely incident shear waves. • A modified foundation beam model is used for the tunnel longitudinal response, with considering different tangential contact conditions. • By adopting wave theory and Fourier transform, longitudinal response of tunnels under arbitrary seismic load can be obtained. • Moreover, the flattening effect and out-plane response of tunnel cross-section caused by longitudinal bending are considered. • Parameter studies are conducted to investigate the effects of incident angle, ground condition and contact condition. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 (LMA) with magnetoplumbite structure has been identified as a potential candidate for the next generation of thermal barrier coatings (TBCs). However, the as-sprayed LMA coating presents a large amount of amorphous phase originating from the rapid quenching from the molten droplets, which may compromise the reliability of coating during high-temperature service. A logical approach to improve LMA TBC life, therefore, is to enhance its crystallinity. In the present study, three LMA powders with different particle size distributions (fine, medium and coarse feedstocks) were utilized to deposit TBCs to investigate whether the thermal durability of LMA can be improved by increasing particle size. It was based on a hypothesis that large particle size can decrease the melting degree of in-flight particles and thus result in high crystallinity of as-sprayed LMA coating, making less recrystallization stress to enhance the thermal shock resistance of LMA coating. Results show that prolonged thermal cycling durability can indeed be achieved by increasing particle size. However, excessive particle size could lead to higher porosity derived from unmelted particles, which function as the weak regions for the coating system, thereby damaging the structural integrity and adhesive strength between the topcoat and bond coat. This could cause microcrack linking when the accumulated thermal stress exceeds its fracture toughness under consecutive heating-cooling cycles despite its higher crystallinity. Concerning the coating fabricated by medium powder, it achieves the optimal balance of crystallinity and structure integrity, resulting in the longest thermal cycling lifetime. The results provide guidance for the development and design of high thermal durability LMA TBCs. When optimizing the recrystallization stress within the coating, attention should be paid to improving its bonding strength simultaneously. [ABSTRACT FROM AUTHOR]

This study aims to analysis the longitudinal seismic responses of circular tunnels across soil-rock stratum longitudinally ("soil-rock" means two different stratums, not just the soil and rock ground). Based on an improved elastic foundation beam model, an analytical solution is derived to investigate the seismic response of long tunnels across soil-rock stratum, subjected to sinusoidal shear motions. The improved elastic foundation beam model adopts the Timoshenko beam and Winkler foundation, with considering tangential contact conditions at the ground-tunnel interface. The free field reaction considers the reflection and transmission by the soil-rock interface and the wave passage effect. Explicit formulations are obtained for tunnel displacement, rotation angles, bending moments and shearing forces. The proposed solution is verified by comparing with the dynamic numerical results, as well as traditional analytical solutions. Finally, a parametric study is conducted to investigate the influence of traveling wave effect, earthquake frequency, shear wave velocity ratio of two stratums, lining stiffness and contact condition on tunnel seismic responses. The proposed analytical solutions can be used to predict the longitudinal seismic response of deep circular tunnels crossing soil-rock stratum in engineering design. [ABSTRACT FROM AUTHOR]

As a common type of foundation in ocean engineering, steel foundation encounters great corrosion risk and serious safety hazards throughout its lifecycle. Besides reducing the thickness of steel members, corrosion also has a significant impact on the soil-structure interfacial shearing property by changing the roughness characteristics of steel surface, and eventually affects the bearing capacity of steel foundation in submarine soil environment. In this study, electrolytic accelerated corrosion experiments are conducted first to prepare corroded steel samples suffered different degrees of corrosion. Then, the effect of corrosion on the soil-steel foundation interfacial shearing property is investigated by interfacial shearing experiment and discrete element numerical simulation. The analysis results show that the interface shearing strength under different corrosion degrees can be regarded as following Mohr-Coulomb strength theory. The shearing strength parameters, i.e. the interfacial cohesion and interfacial friction coefficient, increase with the corrosion degree. Finally, the influences of corrosion on the bearing capacity of a steel pipe pile foundation are studied by finite element simulation, with considering the steel thickness reduction and the variation of soil-steel interfacial shearing strength. The numerical results demonstrate the necessity of considering the variation of the interfacial shearing property induced by corrosion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning is used to predict geological condition in super-large SPBM tunnel. • Performance of RF, SVM and AdaBoost in rock mass classification is evaluated. • Performance of seven formation prediction models is compared. • Slurry system parameters and cutter type are important for geological prediction. Real-time and precise prediction of geological conditions is extremely beneficial to the safe and efficient construction of slurry pressure balanced shield machines (SPBMs), especially for super-large diameter tunnels. Machine learning algorithms provide an effective way to predict geological conditions and have been successful in hard-rock tunnel boring machine (hard-rock TBM) tunnels or earth pressure balance shield machine (EPBM) tunnels. However, the effectiveness of machine learning in predicting geological conditions for super-large diameter SPBM tunnels is still unknown. This study systematically demonstrated the application of machine learning algorithms to the prediction of geological conditions in super-large diameter SPBM tunnels based on field data from the Heyan Road crossing river tunnel. The relationship between SPBM parameters and geological conditions was first evaluated, and subsequently, an adaptive model was proposed to determine the number of input variables. The performance of three algorithms, random forest (RF), AdaBoost, and support vector machine (SVM), in rock mass classification, and seven algorithms, multi-objective random forest (MORF), single-target-RF, regressor chain-RF, single-target-AdaBoost, regressor chain-AdaBoost, single-target-SVM, and regressor chain-SVM, in formation percentage prediction, were compared. The results showed that machine learning algorithms can effectively predict the geological conditions in super-large diameter SPBM tunnels. Specifically, RF had the best performance in rock classification compared with AdaBoost and SVM. MORF outperforms the other six algorithms in terms of formation percentage prediction. Additionally, sensitivity analysis indicates that the newly proposed parameters, including slurry system parameters and cutter type, have a clear positive effect on the performance of geological condition prediction. [ABSTRACT FROM AUTHOR]

An analytical solution can easily and quickly give the internal forces in tunnels due to seismic waves, by which, the relationship between the key parameters could also be clarified. These methods are widely used in preliminary seismic design of tunnels. This paper presents new analytical solutions for thrust and moment of circular composite-lined tunnels with arbitrary layer linings under obliquely incident SV waves and P waves. Wherein, the lining is regarded as a thick-wall cylinder. Moreover, the proposed analytical solutions can consider different contact conditions of the ground-tunnel and lining-lining interface. The new analytical solutions are verified by comparing with the dynamic finite element analysis results. The results show the accuracy and applicability of the proposed analytical solutions. Parametric analyses are performed to explore the effects of the flexibility coefficient δ , incident angle and steel lining on the seismic response of tunnels. [ABSTRACT FROM AUTHOR]

In this study, La 1- x Nd x MgAl 11- x Sc x O 19 (x = 0.1, 0.2, 0.3; abbreviated as LNMAS-1, 2, 3) coatings which are supposed to possess better properties than LaMgAl 11 O 19 (LMA) were plasma-sprayed and their high-temperature performance were comparatively investigated. Results show that addition of Nd3+ and Sc3+ as dopants to LMA endows corresponding coatings with reduced thermal conductivity and enhanced thermal expansion coefficient, while maintaining advantageous phase stability, although still being subjected to amorphization in plasma flame and following crystallization upon high-temperature service. Furthermore, the doping could cause adherence increasing between topcoat/bondcoat, benefiting from improved melting condition, especially in LNMAS-2 and LNMAS-3 coatings, which is related to the specific powder morphology and lowered melting point. During exposure to 1350°C, mechanical performance and structure integrity of doped free-standing LNMAS coatings can be well preserved even after 400 h aging. In thermal cyclic fatigue test, LNMAS-2 and LNMAS-3 coatings undertake thermal cycling lifetime of ∼181 and 191 cycles at 1100°C, respectively, 40% durable than that of LMA coating. These preliminary results suggest that LNMAS-2, 3 might be promising candidates for advanced thermal barrier coating applications. [ABSTRACT FROM AUTHOR]

The nanostructured (8 wt%) yttria stabilized zirconia coatings (n-YSZ) were deposited by atmospheric plasma spraying (APS) to study the effect of moisture degradation on the properties of n-YSZ coatings. Variations in phase composition, microstructure and mechanical properties were comprehensively characterized. The single-edge notched beam method used for fracture toughness testing is sufficiently reliable for evaluating the integral properties of the coatings in this study. Results indicated that the microstructure of the n-YSZ coatings was significantly affected by hydrothermal degradation. Hydrothermal degradation resulted in substantial defects, such as pores and cracks, which severely decreased the mechanical properties of the n-YSZ coatings. In addition, the ceramic coat was in a state of compressive stress, and the stress initially increased and then decreased with increasing degradation time. The variations in the stress of the n-YSZ coatings are closely related to the transformation of tetragonal to monoclinic phase, which is induced by hydrothermal degradation. Additionally, several major mechanical properties of the n-YSZ coatings decreased significantly with the hydrothermal degradation, including fracture toughness from 1.28 ± 0.05 to 0.08 ± 0.01 MPa m1/2, flexural strength from 60.51 ± 2.98 to 4.54 ± 0.14 MPa, and Young's modulus from 21.98 ± 0.96 to 1.46 ± 0.33 GPa. [ABSTRACT FROM AUTHOR]

In this study, HfO 2 -doped Si bond coats with four different compositions were fabricated on the SiC substrates by atmospheric plasma spray (APS) for environmental barrier coating bond coats. The result showed that relatively dense composite bond coats can be successfully deposited by the APS approach using reduced plasma power to avoid the formation of metastable hafnia phases and hafnium silicides. The thermal expansion behavior of the Si-HfO 2 bond coat was investigated. Results indicated that plasma-sprayed Si-HfO 2 bond coats showed a non-linear expansion in air environment due to the oxidation of Si and formation of HfSiO 4. Thermal cycling behavior of the Si-HfO 2 bond coat at 1300 ℃ was also studied. The result suggested that the Si-HfO 2 bond coat with high Si concentration has relatively better thermal shock resistance, owing to its low CTE and better oxidation resistance. The HfSiO 4 formation reaction between hafnia and silica alleviate the volume contraction caused by cristobalite phase transformation. The spallation of the bond coat was attributed to the formation of thermally grown oxides (TGO) and the coefficient of thermal expansion (CTE) mismatch between the bond coat and the SiC substrate. • Four different Si-HfO 2 bond coat with different Si content were deposited on SiC substrate by APS. • Optimum mixture composition found between 20 wt% and 40 wt% Si. • The Si-HfO 2 bond coat with high HfO 2 content accelerate the oxidation of Si. • The HfSiO 4 formation reaction restrain the cristobalite phase transformation. [ABSTRACT FROM AUTHOR]

In order to promote the thermal cycling behavior of SiC f /SiC composites at high-speed gas scour and high-temperature environment, we have prepared three-layer Si/Yb 2 SiO 5 /LaMgAl 11 O 19 TEBCs onto the surface of SiC f /SiC composites using atmospheric plasma spraying (APS) method. Burner rig tests were performed to evaluate the thermal cycling behavior of TEBCs. Results show that after being tested in high-temperature and high-speed burner flame, only a small number of TEBCs cracked and peeled in the external area of TEBCs caused by the thermal stress and the corrosion of water vapor, but TEBCs did not crack and spall in the center area. The failure mechanism of TEBCs was investigated. Microstructure characterization indicated that the penetrating cracks in TEBCs provided the channel for oxygen and water vapor diffusion to SiC f /SiC composites leading to the severe corrosion of substrate. [ABSTRACT FROM AUTHOR]

In this study, a high-entropy RMgAl 11 O 19 (HE-RMA, R = La, Pr, Nd, Sm, Gd) and LaMgAl 11 O 19 (LMA) coatings were fabricated by atmospheric plasma spraying. The phase composition, microstructure, thermal stability, infrared emissivity performance and shock resistance were comparatively characterized. The results showed that doping multiple rare-earth cations could be conductive to enhance the infrared emissivity. The as-sprayed HE-RMA coating exhibited the highest infrared emissivity, which reached up to 0.971 at 1000 °C. The reason for the improvement of the infrared emissivity was attributed to introduced impurity energy level resulting from doping cations, which could reduce the forbidden bandwidth and increase probability of electronic transition. Meanwhile, HE-RMA coating exhibited better shock resistance at 1100 °C due to superior fracture toughness (1.84 ± 0.41 MPa·m1/2) during thermal cycling test at 1100 °C. In addition, HE-RMA coating still exhibited high infrared emissivity (0.932 at 1000 °C) at 1100 °C annealing for 100 h with only a slight reduction. [ABSTRACT FROM AUTHOR]

Growing three-dimensional (3D) metal organic frameworks (MOFs) via heterogeneous epitaxial growth on metal hydroxide arrays are effective for constructing electrochemical sensor. However, the growth of MOFs is difficult to control, resulting in thick and irregular morphologies and even damage the metal hydroxide template. In this work, Cu 3 (HHTP) 2 (HHTP = 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene) films with controllable thickness and morphology were successfully prepared on Cu(OH) 2 nanowire arrays (NWAs) through layer-by-layer (LBL) growth method. We have discovered that the LBL cycle and the reaction solvent composition are crucial for growing homogenous MOF thin films. The Cu 3 (HHTP) 2 based ascorbic acid (AA) sensor, fabricated in ethanol within 10 LBL cycles, generated an ultrahigh sensitivity of 821.64 μA mM−1 cm−2 in the range of 6–981.41 μM, a low detection limit of 60 nM as well as the great selectivity, stability and reproducibility. Moreover, the relative deviation for AA detection in two fruit juices were 3.22 % and 3.71 %, and the test result for human sweat fall within the normal AA concentration range, verifying the feasibility of as-prepared sensor for practical application. [ABSTRACT FROM AUTHOR]

Tunnels, as critical underground infrastructures, often intersect with faults. Field investigations have underscored the susceptibility of fault-crossing tunnels to extensive damages during earthquakes. Hence, large-scale shaking table tests are conducted to investigate the deformation pattern and failure mechanism of fault-crossing tunnels under transverse excitation, particularly in non-rupture scenarios. The dynamic behavior of the tunnel, as expected, is dominated by the surrounding strata. Acceleration responses vary notably across different regions of the fault site. The disparity increases with the increments of seismic intensity and input frequency. The tunnel section at the interface between the fault and the hanging wall manifest the strongest acceleration, where the largest strains of the tunnel and most of the lining cracks also occur, highlighting its vulnerability to seismic vibrations. The damage-induced non-linearity of the tunnel is then identified by the decreasing dominant frequency thereof. The fault-crossing tunnel exhibits unique three-dimensional shearing-torsional deformations, elucidated through the test data and an analytical model. This deformation pattern provides a better understanding of the seismic responses of fault-crossing tunnels under seismic vibrations. • Dynamic responses of fault-crossing tunnels under seismic vibrations are studied by large-scale shaking table tests. • Faults have significant influence on tunnels under seismic vibrations even without rupture. • Vulnerable region of the tunnel, which is most intensely affected by the fault, is identified. • Deformation pattern and failure mechanism of fault-crossing tunnels under seismic vibrations are revealed. [ABSTRACT FROM AUTHOR]

A circular tunnel in a homogeneous infinite ground subjected to a vertically incident shear wave with an arbitrary vibration direction in the horizontal plane is considered in this study. A simplified analytical solution with explicit formulations for the deformation and stress of the tunnel lining is presented here. The superposition of two solutions under SH and SV waves are derived first. In the analytical solutions, the tunnel lining is taken as a thick-walled cylinder, which enables more precise forecasts and is much closer to practical engineering than the thin shell model adopted in other previous solutions. Moreover, the analytical solutions consider the slippage effect at the ground-lining interface by introducing a spring-type flexibility coefficient into the interaction force-displacement relationship. The results of the analytical solutions are verified by a comparison with the results of the dynamic numerical solutions via a 3-D ground-lining interaction model under earthquakes; the results show good agreement. By using the analytical solutions, the effects of the vibration direction, ground condition, lining thickness and flexibility coefficient on the seismic response of the tunnel are investigated. Additionally, the appropriate range of seismic wavelengths for the analytical solutions is discussed. The proposed solutions can be applied to the seismic analysis and design of tunnel structures. • Analytical solution is presented for circular tunnel under vertically incident shear wave with arbitrary vibration direction. • The tunnel lining is treated as a thick-wall cylinder, which enable precise forecasts. • Different slippage effects at the ground-lining interface are considered. • Effects of vibration direction, ground condition, lining thickness and flexibility coefficient are investigated. [ABSTRACT FROM AUTHOR]

With the rapid development of ocean engineering, many types of steel foundation have been developed to support above ground structures, which encounter great corrosion risk and serious safety hazards in whole service life. Though lots of studies have been devoted to corrosion loss of sectional area and deterioration of strength, little effect focuses on the surface roughness characteristics of corroded steel foundation in submarine soil, which have significant impact on the soil-structure interaction and even on the bearing capacity of overall structure. Electrolytic accelerated corrosion experiments are conducted to investigate the surface roughness characteristics of corroded steel in marine clay soil. The experiment results show that the roughness parameters, i.e. the arithmetic mean height, the maximum height and the standard deviation, have a S-shape growth with the degree of corrosion represented by mean corrosion depth. Moreover, the probability distribution of corrosion height on each corroded surface is statistically analyzed, which generally follows Gauss distribution. Based on the experimental results and roughness parameter change law, a stochastic model is constructed to reconstruct the surface topography of corroded steel with considering different degrees of corrosion, which is verified by comparing the predicated results with experiment data. The findings of surface roughness characteristics and developed stochastic model are helpful for studying the soil-steel foundation interaction characteristics and bearing capacity of ocean engineering structure with considering the corrosion effect. • Surface roughness characteristics of corroded steel foundation in submarine soil are studied. • Surface roughness parameters have a S-shape growth with the corrosion degree. • Probability distribution of corrosion height generally follows Gauss distribution. • Stochastic model is constructed for reconstructing surface topography of corroded steel foundation. [ABSTRACT FROM AUTHOR]

Atmospheric plasma spraying (APS) was used to prepare three-layer environmental barrier coatings (EBCs) Si/Yb 2 SiO 5 /LaMgAl 11 O 19 (LMA) on a SiC f /SiC substrate. Isothermal aging test of the specimens were performed between 1000 and 1360 °C for 500 h. The flexural strength of the specimens after isothermal aging was investigated. Microcracks and holes were observed in the as-sprayed EBCs because of the shock cooling during the APS process, but reduced after isothermal aging, and the EBCs became denser. At least 80.07% of the flexural strength of the SiC f /SiC substrate with EBCs was maintained after isothermal aging, but only 35.91% strength was maintained without EBCs. In particular, the retention ratio of flexural strength was 90.72% after isothermal aging at 1360 °C, despite a reaction between the layers of the EBCs. All the specimens with EBCs showed "pseudo-plastic" fracture, compared with the brittle fracture of specimens without EBCs. [ABSTRACT FROM AUTHOR]

• The effect of soil-rock interface position on the seismic responses of a subway station structure is investigated. • The mechanism of the most detrimental soil-rock interface position for structural response occurs is explained. • The conclusions drawn from the numerical examples of this paper may be useful for seismic design of subway station structure. For subway stations in a site with thin soil layers on the engineering rock, the lower part of the subway station is embedded in the hard rock mass and the upper part is buried in the soil layers. The presence of the soil-rock interface may lead to significant increase to the seismic responses of the adjacent soil masses and underground structures. In this paper, the effect of the soil-rock interface position on the seismic response of a two-story and three-span subway station structure is investigated by numerical analyses. It is found from the numerical analyses that a most detrimental soil-rock interface position exists and makes the underground structure have maximum responses under a given artificial earthquake motion. For the upper floor, the most detrimental soil-rock interface position is near the middle slab. For the lower floor, the most unfavorable soil-rock interface position is near the bottom slab. Softer site generally leads to greater structural responses under the same intensity of ground motion excitation. On the basis of the above findings, three earthquake motions included above an artificial earthquake motion and other two real earthquake motions and three burial depths of structure are further studied. Same conclusions can be obtained for the structure with different burial depths or subjected to different input earthquake motions. The conclusions drawn from the numerical examples of this paper may be useful for seismic design of subway station structure buried in shallow soil layers on rock. [ABSTRACT FROM AUTHOR]

With the rapid development of underground space, more adverse site conditions are occurring in the construction of underground structures. For example, a subway station passes through longitudinally inhomogeneous geology. When the subway station crosses the interface of soft soil and hard soil, this may lead to the destruction of underground structures. In this paper, three-dimensional (3D) nonlinear seismic response analysis of subway stations crossing longitudinally inhomogeneous geology subjected to obliquely incident P waves is presented based on actual engineering background. The earthquake input method for the longitudinally inhomogeneous site that transforms the site seismic response into an equivalent nodal load is first developed and verified. The viscous-spring artificial boundary is used to simulate the radiation damping effect of infinite domain media. Subsequently, the topographic and geological effects on seismic response of engineering site are investigated. Finally, the failure mechanism of the subway station structure crossing longitudinally inhomogeneous geology under the obliquely incident P waves is revealed. The investigation demonstrates that the plastic zone of site usually appears along the interface between the hard and soft soil media, and appears on the side of the soft soil. The sidewall and bottom slab of the structure experience obvious tensile damage at the interface location between the hard and soft soil media. The results show that topographic and geological effects should be considered in seismic analysis and design of underground structures when the topography and geology change significantly. • Seismic analysis of subway station crossing longitudinally inhomogeneous geology is presented • Earthquake input method for longitudinally inhomogeneous site is developed and verified • Effects of topography and geology on seismic response of site and subway station is studied [ABSTRACT FROM AUTHOR]

Continuous silicon carbide fiber reinforced silicon carbide (SiC f /SiC) ceramic matrix composites are considered promising materials as high-temperature components of advanced aero-engines. However, due to their susceptibility to oxidation and corrosion at high temperature, environmental barrier coatings (EBCs) must be applied on the surface of SiC f /SiC. In this study, Si/Y 2 SiO 5 /LaMgAl 11 O 19 (LMA) multi-layer EBCs were fabricated to protect SiC f /SiC by using atmospheric plasma spraying (APS). The high-temperature tensile fatigue performance of SiC f /SiC with and without EBCs was evaluated. The results indicated that EBCs significantly improved the tensile fatigue properties of SiC f /SiC at high temperature in air atmosphere. Meanwhile the bending strength of specimens after isothermal aging or not was also tested. The multi-layer EBCs in this study may be a promising EBCs system for SiC f /SiC after some improvements. [ABSTRACT FROM AUTHOR]

Analytical solutions based on the elastic foundation beam model for the bending response of circular tunnels under longitudinally propagating shear waves are studied considering the tangential contact conditions at the ground-tunnel interface. First, two kinds of new analytical solutions based on Timoshenko beams resting on Winkler or Pasternak foundations are developed considering different contact conditions at the ground-tunnel interface. The contact conditions are considered by introducing a spring-type flexibility coefficient in the force–displacement relationship. Then, the new analytical solutions, as well as the traditional solutions using Euler or Timoshenko beams on Winkler or Pasternak foundations, are compared with the dynamic numerical results. The new analytical solutions exhibit good agreement with the dynamic numerical results for different contact conditions. However, due to the neglect of the tangential interaction between the tunnel and surrounding ground, traditional solutions are only suitable for predicting the seismic response of tunnels in the full-slip condition. Finally, a parametric study is conducted to investigate the effects of the earthquake frequency, ground condition, lining thickness and contact condition. The proposed analytical solutions can be used to predict the seismic response of circular tunnels under longitudinally propagating shear waves in engineering design. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 -type magnetoplumbite holds great promise to be used above 1300 °C as thermal barrier coatings (TBCs), but its practical application has been restricted because of inferior thermophysical properties. Herein, we focus on optimizing the thermophysical properties of LaMgAl 11 O 19 by simultaneously substituting La3+ and Al3+ ions with Nd3+ and Sc3+ ions, respectively. Results show that the effects of co-substitution on reducing thermal conductivity are pronounced. The thermal conductivities of La 1- x Nd x MgAl 11- x Sc x O 19 (x = 0, 0.1, 0.2, 0.3) ceramics decrease progressively with dopant concentration and a lowest thermal conductivity of 2.04 W/(m·K) is achieved with x = 0.3 at 1000 °C, which is a value superior to pure LMA and even lower than YSZ. The mechanisms behind the lowered thermal conductivity are investigated. Increase of the thermal expansion coefficient is also realized (8.53 × 10−6 K−1 for pure LMA, 9.07 × 10−6 K−1 for x = 0.3, 1300 °C). Most importantly, Nd3+ and Sc3+ combination doping indeed facilitates mechanical properties of La 1- x Nd x MgAl 11- x Sc x O 19 solid solutions as well. It should be noted that Sc3+ doping at Al3+ site plays more effective role in improving thermal properties than Nd3+ does at La3+ site. This work provides a path to simultaneously integrate low thermal conductivity, good phase stability, moderate thermal expansion behavior and excellent mechanical properties on LMA for the next generation TBCs. [ABSTRACT FROM AUTHOR]

The failure mechanism of tunnels crossing faults is a critical issue for tunnels located in seismically active regions. This study aims to investigate the nonlinear response of rock tunnels crossing inactive faults under obliquely incident seismic P waves. Based on the equivalent nodal force method together with the viscous-spring boundary, an incident method for the site, which contains fault and is subjected to obliquely incident seismic P waves, is developed first. Then, based on the proposed incident method, the nonlinear response and the failure process of the tunnel crossing inactive fault are numerically studied. The numerical results show that the failure mechanism of the tunnel crossing inactive fault can be attributed to the combined action of the seismic waves and its associated fault slippage. Finally, parameter studies are conducted to investigate the effects of the wave impedance ratio of the fault to the surrounding rock and the incident angle of P waves. By the parameter analysis, it can be concluded that: (1) with decreasing the wave impedance ratio of the fault to the surrounding rock, the seismic response of the tunnel increases significantly; (2) the seismic response of the tunnel increases first and then decreases with the increasing of the incident angle of P waves. This study offers the insight for further research on the seismic stability of tunnels crossing inactive faults. [ABSTRACT FROM AUTHOR]