Bridge Site Research Articles

Experimental and Simulation Studies of Acetone Detection By Pt-Au Nanofilm Sensors

Introduction Acetone in exhaled breath is a biomarker of diabetes. However, since it is a very stable substance, its detection by chemical sensors has been a challenging task. Alloy nanoparticles have attracted great attention because of their great catalytic performance, and it has been reported that the response to acetone can be improved by functionalizing oxide semiconductors (In2O3) with PtAu nanoparticles [1]. However, the mechanism of better response to acetone has not been fully understood, which is partly because the effects of alloying and supporting materials cannot be separated in the composite material systems. In this study, we demonstrate that PtAu-alloy nanofilms, where the effect of supporting materials is eliminated, show a greater response to acetone than Pt nanofilms. Furthermore, the impact of alloying on sensing performance was studied by high-throughput atomistic simulation with neural network potentials. Method First, we fabricated Pt and PtAu nanofilm sensors. As the Pt and PtAu nanofilms, Pt and Pt/Au were deposited, respectively, by electron beam evaporation method. The thickness of Pt film is 3 nm, whereas Pt/Au thicknesses are 2.5 nm/0.5 nm. The electrodes consisted of 40-nm Pt and 40-nm Au layers, and they were annealed in N2 ambient for 1 hour at 300 oC. XRD measurements were performed to evaluate the alloy states for three samples: Pt (20nm), Au (20 nm), and PtAu (18 nm). The PtAu film for XRD was fabricated by repeating sequential depositions of 5-nm Pt and 1-nm Au three times. All the films were annealed for 1 hour at 300 oC in N2 ambient. The sensor responses to acetone were evaluated by measuring the resistance of Pt and PtAu at 260 oC under the following sequences.i) Dry air (15 min)ii) 1-ppm acetone in dry air (2 min)iii) Dry air (3 min)We applied DC current of 100 µA and the voltage difference between the terminals were measured. To examine the factors that contribute to the difference in sensing performance of PtAu and Pt nanofilms, we calculated the reaction pathway using the nudged elastic band method. All calculations were carried out with PFP version 2.0.0 on Matlantis [2]. DFT-D3 was used to describe the van der Waals interaction [3]. Results Pt, Au, and PtAu samples showed (111) peaks in the XRD analysis. The position of (111) peak of PtAu located between those of Pt and Au peaks, suggesting that PtAu was successfully alloyed. By applying the Vegard’s law, the composition of PtAu was determined to be 0.823:0.177, which is consistent with the thickness ratio. When acetone was exposed, the resistance of the devices decreased. The response of PtAu to acetone was greater than that of Pt. In addition, the responses of Pt and PtAu devices were proportional to the square root of the concentration of acetone. The limit of detections (LOD) determined by 3σ method were 76 ppb for Pt and 14 ppb for PtAu. Discussion We considered that H atoms introduced by CH dissociation of acetone prevent the adsorption of oxygens from the atmosphere and reduce the surface scattering of electrons, leading to a decrease in the resistance of Pt nanofilms. The Nudged Elastic Band method was used to calculate the activation energy of CH dissociation of acetone on the surface of Pt and PtAu. PtAu slab was prepared by replacing Pt atoms partly with Au atoms. The calculations showed that the activation energy for PtAu was 64-meV lower than that of Pt. In the transition state, the dissociated H atom stayed at the bridge site of Pt. When Pt atoms are substituted with Au atoms, the distance between Pt’s at the bridge site expands due to the large lattice constant of Au. As a result, the transition state became more stable on PtAu surface than on Pt surface. In fact, we confirmed that the activation energy was lowered as the Pt-Pt distance increased. Conclusion We demonstrated, for the first time, that PtAu nanofilm sensors show a greater response to acetone than Pt nanofilm. The atomic simulation demonstrated that the dehydrogenation of methyl group of acetone is the fundamental mechanism of the acetone sensing, and that the lattice expansion induced by replacing Pt with Au contributed to stabilize the transition state and to reduce the activation energy. Further optimization of the alloy composition should be essential to achieve a more highly sensitive acetone sensor.

Formation mechanism of CO2 in the production of allyl acetate from propylene on PdCu(111) surface: A DFT study

Allyl acetate is an important organic chemical raw material and chemical intermediate. The gas-phase synthesis of allyl acetate from propylene is currently the most widely used process. So far, no researchers have reported the formation mechanism of CO2, the by-product that accounts for the most in the reaction process, which hinders the optimization of the catalyst and process. In this study, the combination of Density Functional Theory (DFT) and Kinetic Monte Carlo (kMC) was used to systematically study the formation mechanism of CO2 from propylene to allyl acetate over PdCu(111). The possible formation reaction network of CO2 in the reaction process was constructed. The calculation results showed that species are more easily adsorbed near the surface Pd atoms, and the adsorption sites of Pd-Cu bridge sites and fcc sites on PdCu(111) surface are more active. From the perspective of energy barrier, the acetic acid path tends to generate CO2 through chain scission and then dehydrogenation, while the propylene path produces CO2 through first dehydrogenation and then oxidative chain scission. Considering comprehensively, the two most likely paths to generate CO2 from propylene and acetic acid on PdCu(111) are:① CH3COOH→CH3COO→CH3(+CO2)→CH2→CH→C→CO→CO2,②CH3CHCH2→CH2CHCH2→CH2CHCH→CH2CHC→CHCHC→CHCC→CHCCO→CHC(+CO)→CHCO→CO(+CH) →CO2.

Hollow-Structured and Polyhedron-Shaped High Entropy Oxide toward Highly Active and Robust Oxygen Evolution Reaction in a Full pH Range.

High entropy metal oxides (HEO) are superior to many reactions involving multi-step elementary reactions. However, controlled synthesis of hollow-structured HEO catalysts, which offers large surface area and fast mass transfer kinetics, remains challenging and unexplored due to the complicated metal precursors. Herein, a metal organic framework-templated synthesis of hollow-structured and polyhedron-shaped HEO catalysts assembled with ultra-small nanoparticles, with up to ten metal elements, can be achieved, by taking advantage of the ion-exchange method. ZnFeNiCuCoRu-O HEO catalyst displays excellent activity and ultra-stability for oxygen evolution reaction in full pH range, with an overpotential of 170 mV at a current density of 10 mA cm-2 , a Tafel slope of 56 mV dec-1 , and a decay of activity by 7% in 30 h in alkaline medium, as well as a 12% and 8% decay in acidic and neutral medium, respectively. DFT calculation indicates that the energy barrier of the potential determining step on Ru-Fe bridge site is significantly lower than any other Ru-related bridge sites for the unique hollow structured HEO structures. This work highlights the importance of ion-exchange method in preparing highly stable and active hollow-structured HEOs catalysts toward highly efficient energy conversion and storage devices.

Physicochemical structure and micromechanical properties of archaeological wood under alternating dry and wet conditions

ABSTRACT The relationship between physicochemical structure and micromechanical properties of archaeological wood is not understand. For this purpose, the study took the archaeological wood from the Shahe Ancient Bridge site as an example. The physical properties, microstructure, chemical composition, and micromechanics of archaeological wood were evaluated using non-destructive and micro-destructive techniques. The results indicated that the deterioration of Phoebe sp. wood was more severe than that of Abies sp. wood. However, the basic density of Phoebe sp. wood was higher than that of the control sample due to the collapse of cell walls. The cell walls exhibited a variety of destructional forms, such as cavities and collapses, caused by decay fungi and erosion bacteria. The cell cavities and cell walls deposited inorganic substances. Furthermore, hemicellulose and amorphous cellulose were preferentially degraded before crystalline cellulose was degraded, and S-type lignin was more prone to degradation compared to G-type lignin. Due to the changes of cell wall structure, the hardness of the cell walls increased while the elastic modulus of the cell wall decreased significantly. This study may provide a reference for the study of the relationship between cell wall structure and micromechanics of archaeological wood.

Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are -0.56 eV and -0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching -1.64 eV, -1.69 eV, and -3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

Experimental investigation of local scour around complex bridge pier of sea-crossing bridge under tidal currents

To study the process of local scour around the large-scale complex bridge pier under tidal currents, local scour experiments were carried out using the pile group-cap of the Hong Kong-Zhuhai-Macao Bridge (HZMB) as prototypes. The geological conditions at the bridge site were explored and the sampled soil was experimentally analyzed to determine the model sand. Based on the long-term observation data of tidal currents at the bridge site, a harmonic analysis of tidal currents was conducted to obtain the hydrodynamic characteristics of the tidal currents. Then a flume experiment of local scour around the large-scale pile groups under tidal currents was carried out. Research results indicate that the tidal currents velocity at the HZMB site exhibits the characteristic that the falling tide velocity is greater than the rising tide velocity. The frequency of the flow direction in the N and S directions is more significant. The tidal currents at the bridge site belong to the irregular semi-diurnal tide. The maximum depth of scour under tidal currents occurs on the side with highest velocity in the rising and falling tide process, and its value is slightly lower than the value under unidirectional flow. The duration of equilibrium scour under tidal currents is longer than under unidirectional flow. The shape of the equilibrium scour pit under tidal currents has changed from a circular arc shape on the upstream side to a saddle shape with deep ends and shallow middle, and has formed a longer sedimentation zone at both ends of the rising and falling tides compared to the situation under unidirectional flow. The size and layout of the pile foundation have a significant impact on the shape of the scour pits that achieve equilibrium scour.

Landscape values of large-scale civic infrastructure from visitors’ spatial perception: a content analysis

Many studies have investigated the improvement and evaluation of urban landscape development. However, only a few have discussed how to implement and align landscape values embedded in large-scale civic infrastructures, including bridges, railways, and public buildings. Taking the case of four typical large-scale civic structures, including three bridge sites and a dam project, this study explores how the landscape values embedded in these kinds of structures, whether in urban or suburban areas, are perceived by external visitors with different cultural backgrounds. Content analysis combining a quantitative approach with online user-generated reviews of on-site visits is applied and implemented. The interrelated effect of different spatial characteristics on the landscape values in those civic infrastructures is examined. The findings provide insights into efficient strategies to exploit various kinds of civic structures, especially as a promising tourism attraction for domestic and foreign markets, to achieve a more sustainable vision of public spaces in urban or broader contexts.

Experimental and theoretical studies on the reactivity and reaction mechanism of LaMnO3 with CO in chemical looping combustion

LaMnO3 perovskite was developed as a promising oxygen carrier in chemical looping combustion due to its abundant oxygen amounts and excellent thermal stability. The reactivity and reaction mechanism of LaMnO3 with CO were systemically studied based on thermogravimetric experiments and density functional theory calculations. The results indicate that LaMnO3 is reduced to Mn3O4 and La2O3 at 707 °C, and finally to MnO. The weight loss of LaMnO3 is 8.67% during the whole reduction process. The reaction rate of LaMnO3 at low temperature can be improved with the increase of CO concentration. The maximal reaction rate of LaMnO3 with CO increases as the heating rate rises. The higher reaction temperature leads to the complete reduction of LaMnO3. Besides, SEM analysis reveals that LaMnO3 has no sintering-agglomeration phenomenon and exhibits good sintering resistance. Density functional theory calculations indicate that the Mn–O bridge sites are the most favorable for CO adsorption on the LaMnO3 surface. The adsorbed CO reacts with a bridging surface lattice O to generate CO2 precursor, revealing the key intermediate for CO oxidation. CO2 precursor will break through the energy barrier of 56.03 kJ/mol to generate free CO2 molecule.

Numerical and experimental study of a segmentally prefabricated orthotropic steel–ultra-high-performance concrete composite deck for long-span cable-stayed bridges

Utilizing the high strengths, toughness, and durability of ultra-high-performance concrete (UHPC), a segmentally prefabricated orthotropic steel–UHPC composite deck (POSUCD) system has been developed for long-span cable-stayed bridges. The deck system combines an orthotropic steel deck (OSD) with a reinforced UHPC layer using notched perfobond strips (NPBLs). The UHPC layer is prefabricated onto the OSD of the girder segment in the factory to form the POSUCD. After the precast UHPC layer is cured, the girder segments are transported to the bridge site and assembled. The precast UHPC layers are then connected via transverse wet joints before tensioning stay cables. Against the background of the Danjiangkou Reservoir Bridge with a main span of 760 m, finite element (FE) analysis was conducted to examine the stress state and flexural tests were carried out on local full-scale models to verify the feasibility of POSUCD. The results show that the prefabricated UHPC layer reduces the maximum static compressive stress of the steel deck in the girder system by 21%, and the stress ranges at fatigue-prone details of the steel deck are decreased by 28%–90% compared to traditional OSDs with asphalt overlay. Since the prefabricated UHPC layer helps withstand dead axial load in the main girder, the high compressive strengths of UHPC can be utilized more effectively than in deck systems with UHPC only used as a cast-in-situ overlay to resist vehicular wheel loads. The transverse wet joint interfaces were identified as the weakest aspect of the POSUCD, whether under tension or compression; however, their nominal flexural strengths along the longitudinal direction meet the required design standards. The shear resistance of NPBLs was also well confirmed by the minimal interfacial slip on the specimen when it reached the ultimate capacity under positive bending moment.

Understanding Bridging Sites and Accelerating Quantum Efficiency for Photocatalytic CO2 Reduction

HighlightsThe S-vacancies result in the change of d-band electronic state of Mo.An internal quantum efficiency of 94.01% at 380 nm for photocatalytic CO2 reduction reaction (CO2RR).The Mo–S bridging bonds optimize adsorption energies and accelerate CO2RR kinetics.

Exploring the performance of T-graphene for the anode of Mg-ion and Ca-ion batteries: A first-principles study

Due to the growing need for high-capacity ion storage batteries, researchers are exploring new categories of electrode materials with superior electrochemical properties. In this investigation, a tetragonal symmetry of carbon named T-graphene has been taken into consideration as an anode material for Mg and Ca ion batteries for its superior electrical characteristics. To comprehend the adsorption behavior, charge transfer, and anodic properties of T-graphene, density functional theory has been employed. Initially, the most favorable adsorption sites for Mg/Ca insertion on the T-graphene have been identified and it found that bridge and octagonal hollow sites show high adsorption behavior with energy of about −1.99 and −4.86 eV, respectively. A significant amount of charge (Hirshfeld) about 0.24e and 0.79e transfer from Mg and Ca to T-graphene, respectively. When Mg/Ca is inserted, the electronic structure calculations demonstrate that T-graphene acts metallically. A very high specific capacity is found at about 1737.13 and 1985.30 mAh/g for Mg and Ca ion batteries, respectively. Moreover, the average open-circuit voltages for Mg are 0.65 V and 1.51 V for Ca. Therefore, it is assumed that T-graphene may be used as high-capacity anode material for Mg and Ca ion battery.

Surface functionalization of graphene-like boron arsenide monolayer: a first-principles study

In this work, the effects of hydrogen (H) and oxygen (O) adsorption on the electronic and magnetic properties of graphene-like boron arsenide (BAs) monolayer are investigated using first-principles calculations. Pristine monolayer is a non-magnetic two-dimensional (2D) material, exhibiting direct gap semiconductor character with band gap of 0.75 (1.18) eV as calculated by generalized gradient approximation with Perdew–Burke–Ernzerhof (HSE06) functional. Four high-symmetry adsorption sites are considered, including on-top of B atom (), on-top of As atom (), on-top of hollow site (), and on-top of bridge site (). Using the criterion of adsorption energy, it is found that and sites are favorable adsorption sites for H and O adatom, respectively. The analysis of electronic interactions indicate the charge transfer from host BAs monolayer to both adatoms. H adsorption conducts to the emergence of magnetic semiconductor nature in BAs monolayer with a total magnetic moment of 1.00 . Herein, the magnetism is originated mainly from H adatom and its neighbor As atoms. In contrast, the non-magnetic nature of BAs monolayer is preserved upon absorbing O atoms. In this case, the energy gap exhibits a slight reduction of 4%. Further, the effects of adatom coverage are also analyzed. The presented results suggest an effective modification of ground state electronic properties, as well as induction of new feature-rich properties to make new multifunctional 2D materials from non-magnetic BAs monolayer.

Yolk-shell composite oxides with binuclear Co(II) sites toward low-overpotential nitrate reduction to ammonia

Electroreduction of nitrate to ammonia, a potential route for producing ammonia, is still confronted with a great challenge on developing efficient electrocatalysts. In this work, a reduced yolk-shell Co-based oxides (R-Co3O4) electrocatalyst with oxygen vacancy-rich Co3O4 and CoO was designed for nitrate reduction. This catalyst presented a nearly 100 % Faradaic efficiency (FE) of ammonia in a low potential from −0.05 to −0.1 V vs. RHE, and a maximum ammonia production rate of 7.25 mg h−1 mgcat.-1 at −0.05 V vs. RHE in 0.1 M KOH + 1000 ppm KNO3 electrolyte. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) pattern proved that the content of Co2+ was dramatically increased in R-Co3O4. The kinetic correlation experiments and Operando Raman spectra preliminarily manifest that the potential limiting step is the reduction of adsorbed *NO3. The density functional theory (DFT) calculations consistently demonstrated that on both oxygen-rich Co3O4 and CoO, the adsorption of key intermediates (*NO3, *NO and *NH) are greatly enhanced on the bridge site between two Co2+, boosting the nitrate reduction at low over-potential. This work is helpful to design the catalytic material with rich and low-valence sites towards electroreduction of nitrate to ammonia.

Hydrogen Storage Mechanism by Gas-Phase Vanadium Cluster Cations Revealed by Thermal Desorption Spectrometry.

The adsorption of hydrogen on gas-phase vanadium cluster cations, Vn+ (n = 3-14), at 300 K and desorption of hydrogen from hydride clusters, VnHm+, upon heating were observed experimentally by combined thermal desorption spectrometry and mass spectrometry analyses. The ratio m/n was approximately 1.3 for all n values at 300 K, which was reduced to approximately zero at 1000 K. For n = 4, stable cluster geometries of V4Hm+ (m = 0, 2, 4, and 6) were investigated by DFT calculations, revealing that V4 adopted a trigonal pyramidal structure and the H atoms adsorbed mainly on the μ2 bridge sites. The adsorption reaction pathway of one H2 molecule on V4+ was also investigated. The experimentally estimated desorption energies of the H2 molecules were consistent with their calculated binding energies. Among the observed hydride clusters, V6H8+ was found to be significantly thermally durable, probably because of its close-packed octahedral V6 core structure, with H atoms occupying all hollow sites.

Ab initio calculations of electronic, magnetic, optical, and photocatalytic properties of strained 1T–ZrSe[formula omitted]

Because transition metal dichalcogenides (TMDs) can withstand high strain, strain engineering has shown to be an attractive strategy for modulating TMD characteristics and improving device performance. Density functional theory (DFT) was used to perform first-principles calculations on the electronic, magnetic, optical, and photocatalytic properties of a 1T–ZrSe2 monolayer under biaxial compressive and tensile strain. The first-principles computations revealed that all stressed structures experienced a semiconducting to metallic phase transition. Compressive strain resulted in no magnetization, whereas increasing tensile strain resulted in a significant increase in magnetization on 1T–ZrSe2. When 6% tensile strain was applied, the total magnetization changed 3.33 times, from 0.069 μB/cell to 0.184 μB/cell. Dynamic stability was maintained as the compressive strain was increased. However, dynamic stability held up to 10% of applied tensile strain. The vibration peak in Raman spectra shifted to a higher wavenumber which signifies the frequency reduction behavior with increasing tensile strain applied on 1T–ZrSe2. For different high–symmetry adsorption sites of I2 and I–Br on -10% strained 1T–ZrSe2, a noticeable band gap occurred and metallic to semiconducting phase transition was obtained. The bridge site of I2 exhibited significant adsorption energy among all the adsorption sites. This investigation satisfied the oxygen evaluation reaction (OER) condition for all adsorption sites of I2 and I–Br. The findings of this study will come up with novel schemes for 2D–TMD functional materials in numerous applications and propel the research interest in making spintronic and photocatalytic devices.

Mechanistic study of the production of ethylene glycol diacetate as a byproduct of the ethylene vapor phase process for vinyl acetate on PdAu(100) surface

With the rapid development of the photovoltaic industry, the demand for new materials such as EVA resin is increasing, and the study of its synthetic monomer vinyl acetate is of great significance. The ethylene vapor phase process is the current mainstream method for producing ethylene acetate. This method mainly uses a PdAu bimetallic catalyst to catalyze the production of ethylene acetate and water from ethylene, acetic acid and oxygen. The reaction process produces ethylene glycol diacetate, a high boiling point byproduct, which not only increases the energy consumption for separating the byproduct and reduces the selectivity of the target product but also may lead to catalyst deactivation. Therefore, reducing its production is of great importance in industrial production. The production mechanism of ethylene glycol diacetate is not clear due to the large variety of surface species and the complexity of the reaction in the ethylene vapor phase method, which makes it challenging to investigate the production mechanism of ethylene glycol diacetate directly by experimental means without interference. Molecular simulation techniques, especially Density Functional Theory (DFT) simulations and kinetic Monte Carlo (kMC) simulations, allow for a targeted study of the catalyst surface reaction mechanism to obtain the mechanism of ethylene glycol diacetate production.In this paper, the elementary reaction in the possible formation path of ethylene glycol diacetate on PdAu(100) surface has been studied by the DFT simulations, and the energy barrier and reaction heat of each elementary reaction have been obtained. Moreover, based on the DFT simulation data, the generation process of ethylene glycol diacetate on PdAu(100) surface is investigated by the kMC simulation, including the processes of reactant adsorption, intermediate species diffusion, surface reaction, and product desorption. The calculation results show that the species are mainly adsorbed on the Pd-Au bridge site or Pd top site; ethylene can firstly generate CH3COOCH2CH2, CH3COOCHCH2 or CH3COOCHCH species and then be combined with CH3COO species to produce ethylene glycol diacetate, where the energy barrier of the reaction of CH3COOCH2CH2 species with CH3COO species is lower than other two species with CH3COO species. The advantage generation path for the ethylene glycol diacetate on PdAu(100) surface is CH2CH2→CH3COOCH2CH2→CH3COOCH2CH2OCOCH3, and the rate-determining step is the reaction of ethylene with CH3COO species to form CH3COOCH2CH2 species.

Structural and electronic characterization of Pb adsorption on clean and Cr or Ni doped Fe(1 0 0) surface: An ab-initio study

Using ab-initio calculations, the interaction of lead adatom on both the clean and doped iron (100) surfaces has been investigated. The adsorption energies show that the hollow site provides a more stable configuration with respect to the top and bridge sites, and, in this position, the lead adatom is more energetically favourable than the iron adatom. On the other hand, lead adsorbed in the hollow site of the iron (100) surface doped with chromium, provides more stable system than the nickel doped surfaces with an iron atom adsorbed in the same position. Detailed investigations of inter-layer distances, bonding mechanisms in terms of the projected density of states, magnetic behaviours, and charge density differences are also presented. Our results give insights in the role of the doping the interaction between lead adatom and iron surface, and then, this study may be exploited in the analysis of the corrosion process due to liquid lead.

Impact analysis of repeated improper treatment of bridge site slopes to bridge across

The bridge site slope in Zhengjiawan has been renovated several times in response to the adverse geological conditions of the Zhengjiawan ancient landslide (ZAL) in China. However, improper control and treatment measures have caused the structural failure of the Zhengjiawan bridge (ZB). Based on long-term field monitoring data of rainfall, temperature, bridge deformation, and bridge site slope displacements, this paper analyses the impact of repeated improper treatment on bridge site slopes to bridge across. Furthermore, it summarized the interrelationship between bridge deformation and bridge site slopes under natural rainfall and improper treatment measure conditions, and proposed a set of solutions for bridge site slope control and treatment. The results show that the destruction of ZB is primarily attributed to the deformation of ZAL, natural rainfall is the main trigger controlling the intermittent creep of the ZAL, while the construction of anti-slide pile and deviation rectification of bridge abutment result in significant deformation of ZAL. The deformation of ZB and ZAL were synchronous, and the monthly displacement difference ranged from 0.18 to 5.19 mm. The failure of the ZB structure resulting from the ZAL is attributed to the insufficient shear strength of the weak loose soil comprising the landslide, which fails to withstand the sliding force induced by continuous heavy rainfall. Additionally, the original anti-slide pile inadequately controls the deformation of the landslide. By setting the second-row anti-slide pile, adding the cross-sectional area of the bridge pier foundation, and installing drainage pipes, the safety of the bridge is effectively guaranteed. The control and treatment of ZAL show that preventing bridge pier deformation should be prioritized followed by controlling and treating bridge site slopes, and this study provides insights into interactions between unstable landslide treatments and bridge structures which may serve as a reference for similar projects.

Rapid damage assessment of regional beam bridges after earthquake based on simplified models and different seismic inputs

As the hub of the traffic network, the rapid damage assessment of bridges after earthquake is of great significance for post-disaster rescue. Traditional vulnerability-based method can only provide the probability of different damage states of structures under different earthquake intensity indicators, which confuses the selection of post-disaster rescue routes. Therefore, this paper proposes a post earthquake damage assessment technique for regional bridges based on nonlinear dynamic time-history response analysis. First, a simplified mechanical model for a single pier was established for a large number of beam bridges in the region, achieving standardized and batch rapid finite element model establishment. Secondly, using Kriging interpolation method and continuous wavelet transform technology, the surface seismic response of geological drilling points is calculated to obtain the seismic motion history of any bridge site in the region. Finally, using parallel computing technology, nonlinear dynamic time-history response analysis was conducted on the simplified beam bridge model, and the bridge damage status was quantitatively evaluated based on the calculation results. Eighty-five bridges in a specific area are considered as an example to verify the proposed method. The results show that the proposed method has high calculation efficiency and can consider the site characteristics and structural design parameters. Also, the calculation results can better reflect the actual earthquake damage distribution, providing strong technical support for post-disaster rescue.

Structural Modeling of O/F Correlated Disorder in TaOF3 and NbOF3-x(OH)x by Coupling Solid-State NMR and DFT Calculations.

The structure of MOF3 (M = Nb, Ta) compounds was precisely modeled by combining powder X-ray diffraction, solid-state NMR spectroscopy, and semiempirical dispersion-corrected DFT calculations. It consists of stacked ∞(MOF3) layers along the c⃗ direction formed by heteroleptic corner-connected MX6 (X = O, F) octahedra. 19F NMR resonance assignments and occupancy rates of the anionic crystallographic sites have been revised. The bridging site is shared equally by the anions, and the terminal site is occupied by F only. An O/F correlated disorder is expected since cis-MO2F4 octahedra are favored, resulting in one-dimensional -F-M-O-M- strings along the <100> and <010> directions. Ten different 2 × 2 × 1 supercells per compound, fulfilling these characteristics, were built. Using DFT calculations and the GIPAW approach, the supercells were relaxed and the 19F isotropic chemical shift values were determined. The agreement between the experimental and calculated 19F spectra is excellent for TaOF3. The 1H and 19F experimental NMR spectra revealed that some of the bridging F atoms are substituted by OH groups, especially in NbOF3. New supercells involving OH groups were generated. Remarkably, the best agreement is obtained for the supercells with the composition closest to that estimated from the 19F NMR spectra, i.e., NbOF2.85(OH)0.15.