3D Tunnel Research Articles

Differences for Cooling Capacity of a Cable Tunnel System: Install One or Three Additional Cable Troughs with Cable Circuit for 100/70 Heat Loads – A Numerical Study

The purpose of this report was to compare the numerical analysis for different cooling efficiency of a cable tunnel system when installing one additional cable trough or three cable troughs for cable circuit 100% or 70% heat load. Cable tunnel system is widely known for it is use for high voltage transmission in an underground. Due to the cables generating large quantities of heat, water pipes and air ventilation were used in the tunnel to cool down the transmission cable. To investigate the cooling efficiency of a tunnel, research for benchmark case was carried out. A Computational Fluid Dynamic (CFD) benchmark analysis about 2D natural convection inside the square cavity was investigated to further understand the air movement inside the square medium. Ansys Fluent was carried out for benchmark cases of heat transfer natural convection inside the square cavity and to check whether Ansys Fluent can be used for any CFD and heat transfer purposes by validating the results with previous studies. The benchmark case used a 2D square with different active temperature side walls and adiabatic walls for top and bottom side. From the benchmark simulations with different Rayleigh Number, a number representing buoyancy-driven of a fluid from 103 to 105 affected air differently and the heat transfer natural convection inside the square. At different Rayleigh Number air forms a recirculation passing the active walls and adiabatic walls. After investigated the benchmark, the results were used to validate with previous studies. To validate the results was by using Nusselt Number, ratio of convective to conductive. The benchmark case results were validated and Ansys Fluent proven can be used for CFD and heat transfer purposes. Two 3D cable tunnel were modelled with 100-meter length after concluded the benchmark. The two tunnel models were based on the number of cable troughs installed. The first tunnel was with one cable trough and two cable circuits on the bottom, as for the second tunnel was with one bottom cable circuit and three cable troughs. Cable tunnel simulations were based on cable circuit for 100% heat load and 70% heat load with each heat load case was given different water flow rate of 4.25 L/s and 6.5 L/s. A total of eight scenario cases were carried out to determine which provided a better cooling efficiency choice. The analysis for cable tunnel cases on how the copper cables cooled down through heat transfer of natural convection inside the cable trough, which the heat then was removed from the cable circuit by air and continue to the outside of the tunnel. During the heat transfer processes, conductivity was present as not all heat were removed by air and water, but continue to through the walls of the tunnel and to the ground soil. Based on the simulations, a cable tunnel with three cable troughs was proven more cooling efficiency compared tunnel with one cable trough. Some scenarios did not meet the criteria, due to insufficient heat relocation by air and water. The cooling efficiency was determined by which has the better balance heat relocation by air, water, and ground, also considering the comfort and safety of human inside the tunnel.

Simulation of High-Voltage Cable Sheath Current with a Panoramic Digital Tunnel Model

Monitoring cable sheath current is crucial for guaranteeing the secure and efficient operation of high-voltage cable tunnels. In this study, a three-dimensional (3D) panoramic digital model of a tunnel in Beijing is modeled, a parallel cable sheath current simulation model is proposed, and a 3D panoramic visualization system with which the cable sheath current can be simulated online is developed in order to generate early warnings on the sheath current situation. The accuracy of the simulation model is verified and the results are as follows: The difference between the simulated sheath current and the actual measurement is within a maximum margin of 3.71%. A phase sequence optimization strategy can be obtained after calculations based on the simulation model, and an average sheath current reduction of 47.2% can be achieved following the optimization strategy. This study introduces a new approach by which cable sheath current dynamics and real-time warning against anomalies are visualized on a 3D tunnel model. In addition, a sheath current simulation model is integrated in the 3D visualization system developed in this study, and phase sequence optimization strategies for cables with abnormal sheath currents are automatically suggested, which may provide scientific support for auxiliary decision-making in real-time cable operation.

Effects of Turbulence Modeling on the Simulation of Wind Flow over Typical Complex Terrains

The correct prediction of the wind speed and turbulence levels over complex terrain is essential for accurately assessing wind turbine wake recovery, power production, safety, and wind farm design. In this paper, two modified RANS turbulence models are proposed, which are innovative variants of the conventional SST k-ω model and the linear Reynolds stress model (RSM) featuring optimized closure constants. Then, these two modified models and their origin models are applied to compare and analyze wind flows from a 3D hill wind tunnel experiment and two field measurements over typical complex terrain, including Askervein hill and Bolund island, with the aim of analyzing the sensitivity of wind flows to different RANS turbulence models. The study focuses on analyzing the effects of different turbulence models on the self-sustainability of wind speed and turbulent kinetic energy upstream of the computational domain and on the accuracy of wind flow prediction over complex terrain. The results show that our modified RSM model shows better agreement with the available experimental data on the upstream and leeward sides of all simulated hills. The wind speed on the leeward slope is particularly sensitive to the turbulence model, with a maximum difference in the relative root mean square error (RRMSE) that can reach 11% among the four models. The accuracy of the turbulent kinetic energy depends on the self-sustainability of the upstream turbulent kinetic energy and the predictive ability of the turbulence model for separated flows, and the maximum difference in the RRMSE of the four models can reach 47%. In addition, the advantages and disadvantages of the tested models are discussed to provide guidance for model selection during wind flow simulations in complex terrain.

Reducing Lithium‐Diffusion Barrier on the Wadsley–Roth Crystallographic Shear Plane via Low‐Valent Cation Doping for Ultrahigh Power Lithium‐Ion Batteries

AbstractRapid‐charging niobium–tungsten oxide Nb14W3O44 (NbWO) anodes with a Wadsley–Roth crystallographic shear (WRCS) structure possess 3D interconnected open tunnels. However, the anisotropic Li+ diffusion paths lead to a high lithium‐diffusion barrier of hooping between window sites across edge‐shared octahedrons, as the rate‐limiting step of hooping. To improve the rate capability of NbWO, doping it with low‐valent cations (with valences lower than W6+) to reduce the high lithium‐diffusion barrier is proposed. Electron energy loss spectroscopy reveals that low‐valent V5+, V4+, Tb4+, and Ce4+ tend to distribute on the crystallographic shear plane under electrostatic repulsion forces. The reduction in steric hindrance resulting from the increased long bond length ratio of doped edge‐shared octahedrons, coupled with coordination environment modification of [LiO5] on the crystallographic shear plane due to the low energy level of V5+, enhances Li+ diffusion kinetics and cyclic stability. V5+‐ and Tb4+‐doped NbWOs achieve rate capacities of 83 and 63 mAh g−1, at 200 C (1C = 0.178 Ag−1) and retain 75.42% and 86.79% of their capacities, respectively, after 3700 cycles at 20 C. Thus, the proposed doping strategy is promising for preparing WRCS‐type niobium‐based oxides for ultrafast lithium storage.

Alluaudite chemistry: From Intercalation to Conversion

Alluaudites, a naturally occurring mineral, are best known as the intercalation-based cathode materials in the field of sodium-ion batteries.1 The 3D tunnel like structure of alluaudite facilitates easy alkali-ion migration making it (de)insertion host. The structural formula can be expressed as A(1)A(2)M(1)M(2)2(XO4)3, where A and M sites are alkali and transition metal ions respectively and XO4 denotes the polyanionic moieties (SO4, PO4, AsO4, MoO4, WO4 and so on). Depending on the inductive effect of the electronegative element, the potential of the materials can be tuned. In 2014, Yamada group reported alluaudite-structured Na2Fe2(SO4)3 as 3.8 V cathode material which benchmarked the highest potential ever observed by Fe2+/Fe3+ redox couple because of the presence of electronegative SO4 moiety.2 In 2017, the first molybdate-based alluaudite material, Na2.67Mn1.67(MoO4)3 was reported as a 3.45 V cathode by probing Mn2+/Mn3+ redox.3 Except Mn, Mo can also serve as another redox centre by using its range of oxidation states from +6 to 0. However, there is an open question remains whether we can access these redox states of Mo to impart extra capacity in these materials.To address the above issue, two case-studies will be discussed. Molybdate alluaudite: A series of molybdate-based alluaudites (TM= Co, Ni) were synthesized by using wet-chemical solution-combustion route. The Co-based alluaudite, Na36Co1.32(MoO4)3 was found to act as a high-voltage cathode (4 V vs Na/Na+ and 4.1 V vs Li/Li+) involving Co3+/Co2+ redox center while cycling between 3.0 V to 4.3 V.4 An intercalation-type of mechanism was proved by ex-situ studies combined with first principle calculations. All the above-mentioned alluaudite consists of Mo species, which can be redox-active at lower voltage. When cycled in a low-voltage window (0.01 V to 3.0 V), Na3.36Co1.32(MoO4)3 was found to act as an anode in Na-ion batteries. High capacity (ca. 400-500 mAh/g) was obtained with a central potential ~0.6 V involving conversion and (de)insertion reaction mechanism. The Ni-analogue, Na3.6Ni1.2(MoO4)3 alluaudite, was studied as an anode material in both Li-ion and Na-ion batteries involving conversion and (de)intercalation redox mechanisms like the Co analogue. The underlying redox mechanism will be described for both cases involving post-mortem diffraction, electron microscopy, and spectroscopic tools along with density functional theory (DFT) calculations. Tungstate alluaudite: The first-ever tungstate alluaudite, Na4Mn(WO4)3, prepared by a solid-state route, was found to work as a 0.4 V anode (vs. Na+/Na) material while cycled in the voltage window of 0.01 V to 3.0 V. Similar to molybdenum, W can also show multiple redox chemistries. A conversion- type mechanism was probed with the help of in-situ XRD, ex-situ TEM, XAS and XPS techniques.

Towards 3D Reconstruction of Multi-Shaped Tunnels Utilizing Mobile Laser Scanning Data

Using digital twin models of tunnels has become critical to their efficient maintenance and management. A high-precision 3D tunnel model is the prerequisite for a successful digital twin model of tunnel applications. However, constructing high-precision 3D tunnel models with high-quality textures and structural integrity based on mobile laser scanning data remains a challenge, particularly for tunnels of different shapes. This study addresses this problem by developing a novel method for the 3D reconstruction of multi-shaped tunnels based on mobile laser scanning data. This method does not require any predefined mathematical models or projection parameters to convert point clouds into 2D intensity images that conform to the geometric features of tunnel linings. This method also improves the accuracy of 3D tunnel mesh models by applying an adaptive threshold approach that reduces the number of pseudo-surfaces generated during the Poisson surface reconstruction of tunnels. This method was experimentally verified by conducting 3D reconstruction tasks involving tunnel point clouds of four different shapes. The superiority of this method was further confirmed through qualitative and quantitative comparisons with related approaches. By automatically and efficiently constructing a high-precision 3D tunnel model, the proposed method offers an important model foundation for digital twin engineering and a valuable reference for future tunnel model construction projects.

3D Tunnel Copper Tetrathiovanadate Nanocube Cathode Achieving Ultrafast Magnesium Storage Reactions through a Charge Delocalization and Displacement Mechanism.

Rechargeable magnesium batteries are attractive candidates for large-scale energy storage applications because of the low cost and high safety, but the scarcity and inferior performance of the cathode materials are hindering the development. In the present study, a kind of copper tetrathiovanadate (Cu3VS4) cathode is designed and developed with a comprehensive consideration of the chemical and electronic structures. The vanadium and sulfur atoms form chemical bonds with high covalent proportion, facilitating electron delocalization via the vanadium-sulfur bonds. This reduces the interaction with the bivalent magnesium cation and induces the coredox of vanadium and sulfur. The crystal structure of Cu3VS4 has interlaced 3D tunnels for solid-state magnesium cation transport. The Cu3VS4 cathode shows a high capacity of 350 mA h g-1 at 100 mA g-1, an outstanding rate performance of 67 mA h g-1 at 10 A g-1, and stable cycling for 1000 cycles at 5 A g-1 without obvious capacity fading. Prominently, a high areal mass load of 3.5 mg cm-2 could be achieved without obvious rate capability decay, which is quite favorable to pair with the high-capacity magnesium metal anode in practical application. The mechanism investigation and theoretical computation demonstrate that Cu3VS4 undergoes first a magnesium intercalation and then a displacement reaction, during which the crystal structure is maintained, assisting the reaction reversibility and cycling stability. All the copper, vanadium, and sulfur elements experience redox and contribute to the high capacity. Moreover, the weakened interaction with magnesium cations, well-kept 3D cation transport tunnels, and high electronic conductivity result in the superior rate performance and high areal active material loading. The present study develops a high-performance cathode for rechargeable magnesium batteries and reveal the design principle based on both of chemical and electronic structures.

Unveiling the Influence of Water Molecules on the Structural Dynamics of Prussian Blue Analogues.

3D-framework Prussian blue analogues (PBAs) are appealing as a cost-effective, sustainable cathodes for Na-ion batteries. However, the aqueous-based synthesis of PBAs inherently introduces three different forms of water molecules (surface, interstitial and crystal) into the structure. Removal of water molecules causes phase transformation from monoclinic (M) to rhombohedral (R). This work presents the effects of water molecules on the structure before the phase transformation temperature, employing two promising PBA cathodes, Na2Fe[Fe(CN)6]·1.69H2O and Na2Mn[Fe(CN)6]·1.76H2O. Specifically, the water molecules impact the molecular interactions at the local structure and the electrochemical properties. This work has performed calculations on low-vacancy Na2M[Fe(CN)6] PBAs (where M = Mn, Fe, Co, Ni and Cu) to understand the dehydration energy. Employing in situ high-temperature X-ray diffraction and Raman spectroscopy, this work observes that water removal induces negative thermal expansion and stronger interactions between C≡N and Na ions, resulting in biphasic reactions with sluggish kinetics. Additionally, water molecules play a role in maintaining the open 3D tunnels and facilitating a solid-solution like insertion of Na ions. Calculated phonon-Raman spectra provide insights into cyanide group deformations, revealing the interactions between water molecules, alkali-ions, and transition-metal ions. This study enhances the understanding of the relationship among electronic, vibrational, and electrochemical properties.

Cu3VSe4 Cathode for Rechargeable Magnesium Batteries: Favorable Chemical and Electronic Structures Inducing Intercalation and Displacement Reactions

AbstractRechargeable Mg batteries are an advantageous energy‐storage technology with low cost and high safety, but the design of high‐performance cathode materials is currently the major difficulty. Herein, a new cathode material of Cu3VSe4 is fabricated with a comprehensive consideration of the chemical and electronic structures. The intermediate band semiconductor Cu3VSe4 has a cubic crystal structure containing interlaced 3D tunnels. The V and Se atoms form chemical bonds with high covalent proportions and facilitate the charge delocalization via the V‒Se bonds. Because of these features, Cu3VSe4 provides a high capacity of 251 mAh g‒1 with co‐redox of Cu, V, and Se elements and an outstanding rate performance of 44 mAh g‒1 at 15 A g‒1. Prominently, a high mass load of 3.0 mg cm‒2 is achieved without obvious rate capability decay, which is quite favorable to pair with the high‐capacity Mg metal anode in practical application. The mechanism investigation and theoretical computation demonstrate that Cu3VSe4 undergoes first a Mg‐intercalation and then a displacement reaction, during which the crystal structure is maintained, assisting the reaction reversibility and cycling stability. These findings reveal a rational design principle of rechargeable Mg battery cathodes based on a comprehensive consideration of chemical and electronic structures.

Improved Subsidence Assessment for More Reliable Excavation Activity in Tehran

This paper presents a particular tunneling method, the new Austrian tunneling method (NATM), which plays an important role in reducing subsidence of the surface and damage to structures in urban areas. It has a wide range of applications in shallow tunneling projects all over the world. In this study, numerical modeling of the third-line Metro tunnel in Tehran, which is designed and stabilized by the NATM, is under discussion. The foregoing tunnel is excavated manually with a one-meter advancing step. In this project, the constructors use a lattice girder and spray concrete with 31 cm thickness as the initial lining. A suitable numerical software for this modeling is PLAXIS 3D Tunnel, which allows high-resolution finite element modeling (FEM) of the studied object. The performance of this method is investigated and compared with that of other NATMs. The numerical modeling yielded a value of 30.01 mm for earth subsidence in the most damaged area of the settlement, which was confirmed with a dramatically low difference by earth surface monitoring. Moreover, this tunnel was drilled and excavated using various methods, among which the least settlement was obtained by the proposed method. The results are promising, and they indicate that tunneling with this method should continue to be used to expand the subway line in the city.

Behavior of hydrofoil cavitation in a slit channel

The paper presents the results of a cavitation in a slit channel study and offers an analytical description of cavity development. Special emphasis was placed on examining partial cavitation near a NACA 0012 hydrofoil (NACA – the National Advisory Committee for Aeronautics) inside slit channels of different geometries. Experimental investigation was carried out via high-speed imaging and the laser Doppler anemometry (LDA) method. The experimental data showed that the local flow velocity in hydrofoil leading edge area increased abruptly under arising cavitation. In addition, occurrence of cavitation raised flow velocity pulsation by 20%. In the case of a shorter channel, cavity growth occurred at higher cavitation numbers than for a longer channel. The cavity growth velocity was higher for a shorter channel. We showed that the tendency of partial cavitation development in the slit channel can be described as follows: L/C ∼ σ−1, where L is the cavity length; C is the hydrofoil chord; σ is the cavitation number; and parameter A changes as the slit channel length is varied. Comparison of cavitation development near hydrofoil at different attack angles α inside the slit channel with a three-dimensional (3D) cavitation tunnel was conducted. Cavitation in the slit channel occurred at lower σ/2α values compared to 3D cavitation flow around the hydrofoil. To directly compare lengths of the attached cavities arising in slit channels and 3D cavitation tunnels, an additional parameter is proposed, taking into account friction of the slit channel: K = λ·l/D. This parameter allowed us to quantitatively compare the characteristics of cavitating hydrofoils in slit channels and 3D tunnels. The paper provides the governing criteria of the cavitation in the slit channel. Our results propose the physical foundations for the development of cavities in the slit channel.

Three-Dimensional ERT Advanced Detection Method with Source-Position Electrode Excitation for Tunnel-Boring Machines

Tunnel-boring machines (TBMs) are widely used in urban underground tunnel construction due to their fast and efficient features. However, shield-tunnel construction faces increasingly complex geological environments and may encounter geological hazards such as faults, fracture zones, water surges, and collapses, which can cause significant property damage and casualties. Existing geophysical methods are subject to many limitations in the shield-tunnel environment, where the detection space is extremely small, and a variety of advanced detection methods are unable to meet the required detection requirements. Therefore, it is crucial to accurately detect the geological conditions in front of the tunnel face in real time during the tunnel boring process of TBM tunnels. In this paper, a 3D-ERT advanced detection method using source-position electrode excitation is proposed. First, a source-position electrode array integrated into the TBM cutterhead is designed for the shield-tunnel construction environment, which provides data security for the inverse imaging of the anomalous bodies. Secondly, a 3D finite element tunnel model containing high- and low-resistance anomalous bodies is established, and the GREIT reconstruction algorithm is utilized to reconstruct 3D images of the anomalous body in front of the tunnel face. Finally, a physical simulation experiment platform is built, and the effectiveness of the method is verified by laboratory physical modeling experiments with two different anomalous bodies. The results show that the position and shape of the anomalous body in front of the tunnel face can be well reconstructed, and the method provides a new idea for the continuous detection of shield construction tunnels with boring.

A subway tunnel image stitching method based on point cloud mapping relationships and high-resolution image

The paper presents an intelligent tunnel 3D laser image acquisition system. The system can quickly acquire the 3D point cloud and tunnel surface image of the whole tunnel section. The paper proposes the subway tunnel image stitching method based on point cloud mapping relationships and high-resolution image. Firstly, the method extracts the homonymous points from the mapped image generated from the 3D point cloud and the camera image based on the maximum information coefficient method. Secondly, the 3D point cloud positions corresponding to the homonymous points are determined. The optimization of camera parameters is achieved based on the gradient descent method. Then, the tunnel point cloud is expanded to generate a gray scale image based on spherical projection. Based on the optimized parameters, the point cloud is projected to the camera image to determine the depth value of each camera image pixel point. Finally, the pixel values of the camera image are projected based on the spherical projection to obtain the stitching result images. This method stitches individual images together to form a more complete tunnel surface image. The larger tunnel surface image helps in identifying tunnel defects.

Stability Analysis of Three-Dimensional Tunnel Face Considering Linear and Nonlinear Strength in Unsaturated Soil

The shear strength of unsaturated soils exhibits significant nonlinearity, while previous studies often simplified it with linear strength models. The objective of this paper is to investigate the distinctions in the stability of three-dimensional (3D) tunnel faces when using linear and nonlinear strength models. A new 3D rotational failure mechanism and an extended form of the Mohr–Coulomb (M-C) failure criterion were integrated into the kinematically limited analysis (KLA) framework to describe the failure characteristics of tunnel faces. Subsequently, the factor of safety (FS) of the 3D tunnel faces was calculated using the strength reduction method (SRM). In the discussion section, the impacts of nonlinear shear strength, matric suction in the unsaturated soils, and the 3D geometric parameters of the tunnel on the stability of the tunnel face were analyzed. The outcomes indicate that, in unsaturated soil conditions, diverse nonlinear strength calculation models and soil types exert disparate influences on the FS of 3D tunnel faces. The main novelty of this study lies in establishing an effective method for assessing the stability of tunnel faces in unsaturated soils.

Segmented layered bistable piezoelectric laminates for enhanced energy harvesting from wind‐induced vibration

AbstractIn this study, a segmented layered bistable piezoelectric energy harvester (SBPEH) has been developed and thoroughly investigated for its wind energy harvesting capabilities. The SBPEH's performance was comprehensively evaluated through the creation of a detailed 3D finite element model using Abaqus and XFlow software, and further validated via rigorous wind tunnel experiments. The results of this research demonstrate the SBPEH's remarkable potential for wind energy harvesting. With a wide operational wind speed range, it achieved a maximum measured power output of 5.476 mW, coupled with an outstanding power density of 68.45 mW/cm3, both of which were realized at a wind speed of 13 m/s. It is worth noting that as the wind speed surpasses a specific threshold, the energy harvesting efficiency of the SBPEH experiences a decline, emphasizing the importance of identifying the optimal operational wind speed range for maximizing energy output. These findings offer valuable insights for the enhancement and application of SBPEHs, contributing to the advancement of renewable energy technologies and providing an eco‐friendly solution for power generation.Highlights The study introduces a new segmented layered bistable piezoelectric energy harvester (SBPEH) design for wind energy harvesting, addressing the limitations of traditional harvesters. Performance is evaluated through 3D finite element modeling, ABAQUS, Xflow simulations, and wind tunnel experiments. The SBPEH operates efficiently across a broad wind speed range (6–14 m/s), showcasing optimal output power of 5.476 mW at 13 m/s.

3D Deep Learning for Segmentation of Masonry Tunnel Joints

Historic masonry lined tunnels form a large proportion of the world’s railway tunnel stock. However, as many of these date from the second industrial revolution over 150 years ago, they typically contain large areas of structural deterioration. Masonry spalling is a pervasive form of surface damage and its severity, defined by the depth of spalling, is indicative of a tunnel’s structural condition. Current tunnel spalling condition assessment procedures are largely manual, so the extent of spalling observed on many historic tunnels presents a challenge for timely and cost-effective assessment. Automated machine learning based workflows have shown substantial potential for automating and reducing the subjectivity of the assessment process. A key step in these workflows involves segmenting the location of masonry joints from 3D point clouds of the tunnel lining in order to isolate masonry block locations. The most prevalent method is to unroll 3D tunnel lining data into 2D before applying U-Net based convolutional neural networks to segment joint locations. However, recent developments in 3D point based neural networks enable semantic segmentation to be conducted directly on the input point cloud. Point based methods such as KPCONV provide 3D feature characterization and enable semantic segmentation of a wider variety of tunnel geometries by default, since a handcrafted unrolling strategy is not required. This study conducted a performance comparison between 3D KPCONV, 2D U-Net, and XGBOOST feature classifier based joint identification techniques. In order to effectively compare a real-world use-case where time consuming manual data labelling should be minimized, the methods were only trained on a 9.94m section of tunnel. It was found that a 2D U-Net combined with tunnel unrolling workflow could be more successfully trained on the case study dataset and due to effective transfer learning, achieved superior performance to KPCONV and XGBOOST methods.

In Situ Formation of a LiBO2 Coating Layer and Spinel Phase for Ni-Rich Cathode Materials from a Boric Acid-Etched Precursor.

Ni-rich cathode materials exhibit superior energy densities and have attracted interest among both research and industrial fields; whereas, their practical application is hindered by the intrinsic drawbacks brought by the high nickel content such as structural instability and rapid capacity fading. Herein, in situ formation of a LiBO2 coating layer and spinel phase layer is achieved on the surface of a Ni-rich cathode material via a boric acid etching method at the precursor state. The spinel phase is considered to have a 3D lithium diffusion tunnel and hence faster diffusion kinetics. Moreover, the LiBO2 layer possesses excellent (electro)chemical inertness and can suppress electrolyte decomposition, resulting in a more inorganic and stable cathode-electrolyte interface. The surface reconstructed sample exhibits better cyclic stability (93.3% capacity retention vs 85.3% for the pristine sample at 1 C for 100 cycles) and rate performance. The superiority of this surface reconstruction is demonstrated by a series of electrochemical techniques and characterization methods including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), post-mortem X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations.

Dust raising law of gas explosion in a 3D reconstruction real tunnel: Based on ALE-DEM model

A method based on the combination of finite element and discrete element theories is proposed to reveal the dust raising law of gas explosion shockwaves in 3D reconstructed real tunnels. The influence of a real tunnel's wall structure on shock wave overpressure is simulated and explored, the mechanism of action of the gas explosion shock wave on coal dust particles is revealed. Results indicate Peak overpressure of the fluid near the uneven walls exceeds that at the center of the tunnel by up to 165%. The sharp increase in shock wave overpressure causes a rapid rise in coal dust. Simultaneously, coal dust can decrease the overpressure at the shock wave front by 6.3% to 34.6%. During the shock wave attenuation period, the ratio between the maximum rise height of coal dust and the total displacement decreases as the distance between coal dust and the explosion source increases.

A Photoelectromagnetic 3D Metal-Organic Framework from Flexible Tetraarylethylene-Backboned Ligand and Dynamic Copper-Based Coordination Chemistry.

Porous frameworks that display dynamic responsiveness are of interest in the fields of smart materials, information technology, etc. In this work, a novel copper-based dynamic metal-organic framework [Cu3TTBPE6(H2O)2] (H4TTBPE = 1,1,2,2-tetrakis(4″-(1H-tetrazol-5-yl)-[1,1″-biphenyl]-4-yl)ethane), denoted as HNU-1, is reported which exhibits modulable photoelectromagnetic properties. Due to the synergetic effect of flexible tetraarylethylene-backboned ligands and diverse copper-tetrazole coordination chemistries, a complex 3D tunneling network is established in this MOF by the layer-by-layer staggered assembly of triplicate monolayers, showing a porosity of 59%. These features further make it possible to achieve dynamic transitions, in which the aggregate-state MOF can be transferred to different structural states by changing the chemical environment or upon heating while displaying sensitive responsiveness in terms of light absorption, photoluminescence, and magnetic properties.

Noncentrosymmetric Na6Pb3P4S16 and Centrosymmetric K2MIIP2S6 (MII = Mg and Zn) Displaying Multiple Membered-Ring Configurations and Strong Optical Anisotropy.

Three thiophosphates including noncentrosymmetric Na6Pb3P4S16 and centrosymmetric K2MIIP2S6 (MII = Mg and Zn) were successfully synthesized in vacuum-sealed silica tubes. Note that interesting multiple six membered-rings (6-MRs) including 6-NaS6-MRs and 6-KSn-MRs (n = 6 and 7) formed by A+-centered polyhedra were discovered in the structures of title thiophosphates and these MR-composed three-dimensional (3D) tunnels show great possibility to facilitate the filling of various structural blocks (such as zero-dimensional (0D) Pb3S10 trimers or one-dimensional (1D) (MIISn)n chains). Na6Pb3P4S16 exhibits the strongest nonlinear optical (NLO) response (5.4 × AgGaS2) with phase-matching (PM) behavior among the known Pb-based PM NLO sulfides, which is much larger than that of Pb3P2S8 (3.5 × AgGaS2); it was verified that such large second harmonic generation (SHG) response in Na6Pb3P4S16 can be attributed to the huge contribution of stereochemically active PbS4 units based on the SHG-density and dipole-moment calculations. Moreover, title thiophosphates show large birefringences (Δn = 0.102-0.21), which indicates that incorporation of [P2S6] dimers or polarized PbS4 units into structures provides positive benefits for the onset of strong optical anisotropy.