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High-temperature thermal barrier coating (TBC) materials are desired for the development of high-efficient gas turbines and diesel engines. Herein, to meet up with this requirement, a new class of high-entropy fluorite-type oxides (HEFOs) has been synthesized via a solid-state reaction method. Comparing to La2Ce2O7, a promising TBC material, the HEFOs exhibit similar high thermal expansion coefficients (TECs) of 11.92×10−6∼12.11×10−6 K-1 at temperatures above 673 K but a better TEC matching performance at the temperature range of 473–673 K. It is also found that through tuning the average A-site cation radius, the TEC of the HEFOs could be tailored efficiently. The HEFOs also possess low thermal conductivities of 1.52-1.55 W∙m-1∙K-1 at room temperature, which is much lower than that of La2Ce2O7 and comparable to pyrochlores as Gd2Zr2O7. Moreover, the HEFOs display good sintering resistance and phase stability even at temperatures as high as 1873 K. The combination of these fascinating properties makes the HEFOs good candidates for thermal barrier coating and thermal insulating materials.

The high-temperature mechanical and dielectric properties of Si2N2O ceramics are often limited by the introduction of a sintering aid. Herein, dense Si2N2O was prepared at 1700 °C by hot-pressing oxidized amorphous Si3N4 powder without sintering additives. A homogeneous network with short-range order and a SiN3O structure was formed in the oxidized amorphous Si3N4 powder during the hot-pressing process. Si2N2O crystals preferentially nucleated at positions within the SiN3O structure and grew into rod-like and plate-like grains. Fully dense ceramics with mainly crystalline Si2N2O and some residual amorphous phases were obtained. The as-prepared Si2N2O possessed a good flexural strength of 311 ± 14.9 MPa at 1400 °C, oxidation resistance at 1500 °C, and a low dielectric loss tangent of less than 5 × 10−3 at 1000 °C.

It is very important and effective to characterize the failure mechanism of coal and rock materials from the perspective of energy. Energy dissipation and release are important causes of rock mass failure. To qualitatively and quantitatively characterize the energy evolution process of gas-bearing coal and the energy evolution mechanisms of coal and gas outburst, experimental studies were conducted on gas-bearing coal under different stress paths. The research results demonstrate that the energy evolution of gas-bearing coal has nonlinear characteristics and that the energy density is a quadratic function of stress. The total energy density is mainly stored as elastic energy density and is unrelated to loading paths. According to the distribution characteristics of abutment pressures in a stope, the energy distribution can be divided into an energy dissipation and release zone, an increasing-energy zone, and a stable energy storage zone. During coal mining, abutment pressure in front of the coal wall is an important factor causing energy accumulation, and the stress concentration area is a key area to prevent and control dynamic disasters of coal and rock masses. Furthermore, based on the principle of energy conservation, this study established an energy balance model for coal and gas outburst and derived energy criteria for coal and gas outburst. When $$\Upsilon > 1$$ , there is a risk of coal seams have outburst. If $$\Upsilon = 1$$ , the system is in a state of limit equilibrium, and mining disturbances could trigger outburst.

At present, specific earthquake motion is often used for analyzing the influence of trains on high-speed railway structure; however, the uncertainty of earthquake motion is rarely taken into consideration. In this study, on the basis of considering the uncertainty of earthquake motion, and taking a simply-supported beam with CRTS II track system and CRH2 high-speed train in China as the research objects, a finite element analysis model of vehicle-bridge coupled model was established and verified by tests. The influencing mechanism of the trains on structural response under the action of uncertain earthquake was analyzed, and the range of the influence levels of trains on seismic response of structure was calculated. The research findings show that under the effect of earthquake, the presence of trains decreases the responses of piers and bearings, while increases the response of track structure. With increasing peak ground acceleration, the effect of trains on the track structure deformation increases, while that on the bending moment of piers, shearing force, and bearing deformation all decrease. The increase in train speed will not significantly affect the seismic response of structures. The ratio of seismic response between the operating conditions with and without vehicles was kept within a certain range, so that the demand range for seismic response under the operating condition with vehicles can be approximately simplified.

To verify an increase in porosity due to small pores dose not reduce the dielectric breakdown strength (DBS) of alumina ceramics, we sinter a SiO2-CaO co-doped 95 wt% alumina ceramic via step-controlled atmosphere sintering (first sintering in oxygen, then sintering in air) and conventional sintering (sintering in air) to fabricate samples of different porosities. The dielectric breakdown (DB) test under an AC high voltage shows that the two samples have almost equal DBS in spite of different porosities. Microscopic analysis reveals that the conventionally sintered sample contains more small pores of size range 5–25 μm than the step-controlled atmosphere sintered sample, so the increase in the small pores does not reduce the DBS of the alumina ceramic. The partial discharge in the small pores does not occur before the DB of the alumina ceramic, and this is the reason why the two samples have equal DBS.

Silicon oxycarbide (SiOC) as a prospective electrode material for next-generation lithium ion batteries (LIBs) was restricted by the unsatisfactory discharge capacity and inflexibility used in flexible and wearable electronics. Herein, freestanding flexible SiOC/nitrogen-doped carbon fiber films are constructed through electrospinning process followed by carbonizing in NH3 atmosphere. In this way, SiOC particles are tightly embedded in N-doped carbon fibers, forming a 3D conductive network to promote electron transport and faster reaction kinetics. The nitrogen dopants create more defects in carbon fibers matrix, which improve the electronic conductivity and electrochemical active sites of the electrodes. Owing to the above synergistic effect, SiOC/nitrogen-doped carbon fiber electrodes exhibit a high initial Coulombic efficiency of 73 % and a reversible remaining capacity of 595 mA h g−1 at 200 mA g−1 even after 200 cycles. The electrodes with good flexibility can successfully drive a light-emitting diode even when the package battery is bended to 180°.

Microseismic (MS) source location can help us obtain the fracture characteristics of a rock mass under a thermal-hydraulic-mechanical (THM) coupling environment. However, the commonly used ray-tracing-based location methods are easily affected by the large picking errors, multipath effects of travel time, and focusing and defocusing effects of rays in wavefield propagation, which are caused by the strong three-dimensional (3D) heterogeneity in mining areas. In this paper, we will introduce the rapidly developed waveform inversion-based location method into a mine MS field study. On this basis, the wavefields were modeled by utilizing a high-resolution 3D velocity model, a fractional-order Gaussian wavelet source-time function, and spectral element method (SEM) wavefield modeling. In order to reduce the computation cost of wavefield modeling, the 3D ray-shooting method based on a coarse grid was adopted to obtain an approximate MS event location. Based on this initial location, the multiscale waveform inversion strategy (from coarse to fine grids) and the L-BFGS iteration optimization algorithm were separately jointly selected to improve wavefield modeling speed efficiency and iterative convergence rate. Then, the IMS MS monitoring system set in the Yongshaba mine (China) and its tomographic 3D velocity model were used to conduct the synthetic test and application study. Results show that the source-time function based on the fractional-order Gaussian function wavelet can better fit complex recording waveforms compared with the conventional Ricker wavelet-based source-time function, and the waveform misfit during the L-BFGS iteration decreased rapidly. Furthermore, the multiscale waveform inversion method can obtain a similar location accuracy compared with the waveform inversion based on a single fine grid, and it can significantly decrease the iteration times and wavefield modeling computational cost. The average location error of the eight premeasured blasting events by the proposed approach is only 17.6 m, which can provide a good data research basis for analyzing MS event location and rock mass fracture characteristics in a mine.

Lightweight composites with excellent electromagnetic wave (EMW) absorption performance have attracted increasing attention from researchers. Among these composites, multiwalled carbon nanotubes (MCNTs) are considered as potential candidates, exhibiting excellent dielectric loss, but their magnetic loss is very weak. In our work, we synthesize a one-dimensional chain-like composite with Prussian blue (PB) derived Fe/C anchoring on MCNTs (MCNTs@Fe/C) by two facile processes. The MCNTs are successfully magnetically modified by Fe/C, the derivative of PB, forming an efficient EMW absorbent. The EMW absorption performance is related to complex permittivity and permeability, which can be adjusted by changing the content of PB and MCNTs and the annealing temperature; consequently great attenuation capability and favorable input impedance (Zin) was acquired. The minimum reflection loss (RL) reached − 44.26 dB at 8.32 GHz with a thickness of 2.4 mm, the corresponding absorption bandwidth (RL

Rock often suffers from discontinuous fatigue damages in geotechnical engineering, so it is of great significance to study deformation characteristics and failure modes of sandstone under discontinuous multi-level cyclic loading and unloading. By conducting continuous (only dynamic loading) and discontinuous (combined static and dynamic loading) multi-level cyclic loading and unloading tests, this study explored deformation characteristics and failure modes of sandstone. The test results demonstrated that the sandstone mainly suffered from large deformation dominated by dilation in circumferential direction when it was damaged after compression. After multi-level loading and unloading, evolution characteristics of deformation parameters showed characteristics of stepwise growth. However, the introduction of static loading changed such characteristics. In the process of combined static and dynamic loading, due to short action time, dynamic loading mainly promoted nucleation and sudden changes of cracks, while static loading affected crack development process mainly in the early compaction stage and late crack propagation and coalescence stage. Moreover, static loading showed small effects in elastic stage. In the compaction stage, the compacted micro-cracks reopened and cracks were affected by inertial damages in crack propagation stage and interconnected more thoroughly, so that the sandstone was finally more fragmented.

Although H2O2 has been often employed as a green oxidant for many CeO2-catalyzed reactions, the underlying principle of its activation by surface oxygen vacancy (Vo) is still elusive due to the irreversible removal of postgenerated Vo by water (or H2O2). The metastable Vo (ms-Vo) naturally preserved on pristine CeO2 surfaces was adopted herein for an in-depth study of their interplay with H2O2. Their well-defined local structures and chemical states were found facet-dependent affecting both the adsorption and subsequent activation of H2O2. It is concluded that a strong adsorption of H2O2 on ms-Vo may not guarantee its subsequent activation. The ms-Vo can be only free for the next catalytic cycle when the electron density of surface Ce is high enough to reduce/break the O-O bond of adsorbed H2O2. This explains the 211.8 and 35.8 times enhancement in H2O2 reactivity when the CeO2 surface is changed from (111) and (110) to (100).

The dissociation of natural gas hydrate is an endothermic reaction controlled by the heat transfer, which is closely associated with the employed exploitation methods and well configurations. The m...

MoS2 has emerged as a good application prospect in the electrocatalytic hydrogen evolution reaction (HER). Nevertheless, the catalytic activity of MoS2 is greatly restricted by its inferior electri...

Mechanical properties of rock play a basic and important role in rock dynamic disaster prevention and control as well as rock engineering design and construction. Buried depth is one of the vital factors affecting rock mechanical properties. To study the energy evolution rules during rock failure at different buried depth, static loading experiments under uniaxial compression and dynamic impact experiments at different strain rates and confining pressures were carried out on six groups of granite specimens with different buried depth. Meanwhile, fractal characteristics of rock specimens crushed at different strain rates were also described in the paper. The results indicate that in uniaxial compression experiments, the dissipation energy and energy dissipation rate of rocks show a quadratic curve with the increase of the depth. Moreover, the amount of the dissipation energy during the rock failure is closely related to the buried depth of the rock specimens. In dynamic loading impact experiments, the incident energy, transmitted energy, dissipation energy and absorption energy increase with the rising strain rate and confining pressure. The reflected energy of rock specimens goes up with the increase of the strain rate, while they decrease with the rising confining pressure. As the strain rate gets larger and larger, the fractal dimension increases gradually. The growth amplitude of fractal dimension for the deep rock specimen is significantly greater than that for the shallow one. The specimen fragmentation degree is smaller and smaller, and the fragment particle size gets more and more uniform. From the relationship between various energy and fractal dimension for rock specimens from different buried depth, it can be known that within the buried depth of 750 m~950 m, the k value of incident energy density, transmitted energy density, dissipation energy density and unit absorption energy gradually decrease with the increase of the buried depth. However, within the buried depth ranging from 950 m to 1250 m, the k value of the above energy increases as the buried depth grows.

Photochemical hydrogen generation from water is a promising solution to concurrently tackle energy and environmental problems. However, the solar-to-hydrogen conversion efficiencies of most photocatalysts are still unsatisfactory due to two major limiting factors: the non-ideal band structure of photocatalysts and the fast recombination of photo-generated charge carriers. Herein, we report a Janus-type TiO2 heterojunction consisting of ordered blue-anatase and disordered black-rutile phases fabricated by the magnesiothermic reduction process. In this process, the surface enthalpy difference of rutile and anatase phases in P25-TiO2 allows the phase-selective reduction to afford novel blue ordered/disordered Janus heterostructure. The joint effect of the improved light absorption and charge separation by the disordered black-rutile phase and the high catalytic activity of the ordered blue-anatase phase, as well as the morphological advantage over order@disorder core–shell structures, significantly enhances the photocatalytic hydrogen production rate to 1.56 mmol h−1 g−1 (11.53 mmol h−1 g−1 with ∼1 wt% Pt), which delivers 13-fold enhancement compared to pristine P25-TiO2.

Microseismic source location is a fundamental research interest in real-time microseismic monitoring and hazard risk assessment, and it provides the basis for determining the fracture zones and calculating seismic source parameters of the microseismicity (e.g., the event magnitude, the focal mechanism). In the present work, we carefully relocate some microseismic earthquakes that occurred in the Yongshaba mine (China) using the shooting 3-D ray-tracing (3D-RT) method based on a high-resolution 3-D velocity model, which is determined by a large amount of seismic data. Furthermore, a semiautomatic waveform cut method based on the cross-correlation (CC) technique (WCC) is developed for a quick, robust and precise determination of the direct P-phase relative delay times. Compared with the full waveform cross-correlation (FWCC)-based method, the WCC-based method is free from the influence of complex later-phase waveform spectra. To verify the proposed method, we artificially generate the locations of 892 synthetic microseismic events, the P-phase travel times of which are calculated based on the given 3-D velocity model and the 3-D ray-tracing technique. The relocated hypocentres of these synthetic events obtained by the developed method are improved compared with those obtained by a homogeneous velocity model and the straight line-ray tracing based L1 norm time difference (TD) method (HV-SL-TD1), as well as those obtained by the 3-D velocity model and the straight line-ray tracing based L1 norm and L2 norm TD methods (3D-SL-TD1 and 3D-SL-TD2). Finally, we apply the proposed method to eight experimental blasts with pre-measured locations. The synthetic and application tests show that, despite some multi-path phenomena existing in the ray-tracing methods, the WCC-based method performs as well as the experienced manual picking method, and the results obtained by the 3D-RT location have smaller location errors (~30 m) than those of the homogeneous velocity model-based methods (>40 m). The TD-based method is slightly better than the trigger time (TT)-based method when using the same norm, and the location precision of the L1 norm-based methods have a better resilience to larger picking errors than that of the L2 norm-based methods. Further improvements can be obtained by improving the resolution of the 3-D velocity model and including spatial voids in the model (e.g., tunnels and cavities) for the inversion.

Signal denoising is one of the most important issues in signal processing, and various techniques have been proposed to address this issue. A combined method involving wavelet decomposition and multiscale principal component analysis (MSPCA) has been proposed and exhibits a strong signal denoising performance. This technique takes advantage of several signals that have similar noises to conduct denoising, however, noises are usually quite different between signals, and wavelet decomposition has limited adaptive decomposition abilities for complex signals. To address this issue, we propose a signal denoising method based on ensemble empirical mode decomposition (EEMD) and MSPCA. The proposed method can conduct MSPCA-based denoising for a single signal compared with the former MSPCA-based denoising methods. The main steps of the proposed denoising method are as follows: First, EEMD is used for adaptive decomposition of a signal, and the variance contribution rate is selected to remove components with high-frequency noises. Subsequently, the Hankel matrix is constructed on each component to obtain a higher order matrix, and the main score and load vectors of the PCA are adopted to denoise the Hankel matrix. Next, the PCA-denoised component is denoised using soft thresholding. Finally, the stacking of PCA- and soft thresholding-denoised components is treated as the final denoised signal. Synthetic tests demonstrate that the EEMD-MSPCA-based method can provide good signal denoising results and is superior to the low-pass filter, wavelet reconstruction, EEMD reconstruction, Hankel–SVD, EEMD-Hankel–SVD, and wavelet-MSPCA-based denoising methods. Moreover, the proposed method in combination with the AIC picking method shows good prospects for processing microseismic waves.

Tungsten disulfide (WS2) as one of transition metal dichalcogenides exhibits excellent catalytic activity. However, its catalytic performances in aqueous phase reactions are limited by its hydrophobicity. Here, the natural hydrophilic two-dimensional clay was used to enhance the dispersibility of WS2 in aqueous phase. WS2/montmorillonite (WS2/MMT) composite nanosheets were prepared via hydrothermal synthesis of WS2 on the surface of montmorillonite from WCl6 and CH3CSNH2. The microstructure and morphology show that WS2 nanosheets are assembled parallelly on the montmorillonite with the interface interaction. Through the support of montmorillonite, WS2/MMT possesses higher photocatalytic ability for aqueous phase reactions than WS2, which could be due to the synergistic effect of higher adsorption property, higher hydrophilicity, dispersibility and more catalytic reaction site. The strategy could provide new ideas for obtaining novel hydrophilic photocatalyst with excellent performance.

Varying lower limits cyclic loading and unloading tests with different confining pressures were carried out to reveal the influence of confining pressures on deformation characteristics of sandstones. Increasing confining pressures reduced the development of radial irreversible strain, and increased axial irreversible strain, which prolonged the process of volumetric strain from compression to expansion. The evolution of volumetric strain is sensitive to the division of crack closure, and stable or unstable growth of cracks. Increasing the confining pressure inhibited the development and connection direction of cracks, which decreased the length of the final fracture surface.

Recent studies demonstrate that 2H-WS2 is an excellent candidate for further applications in the electronics, spintronics, and optoelectronics. The details of phonon scattering processes associated...

In deep mine, coal is usually subjected to coupled high gas pressure and static compressive stress. The coal may be also subjected to dynamic loading due to the sudden fracture of hard roof during mining. In our previous study, the behaviour of gas-containing coals with initial gas pressure was investigated subjected to uniaxial static compression. In this study, the dynamic compressive behaviour of gas-containing coals with gas pressure and static axial preloading is investigated using a modified Split Hopkinson Pressure Bar (SHPB) system. The dynamic behaviours of gas-containing coals under SHPB tests are studied by varying initial gas pressure and axial static preloading. The testing results include strain measurements and energy dissipation. In addition, the wave impedance method is used to quantify damage of gas-containing coals under coupled gas-static-dynamic load. It is found that the dynamic compressive strength of gas-containing coal under coupled load decreases with the increasing initial gas pressure. The gas-containing coal with higher gas pressure and axial static preloading is more vulnerable to dynamic loading. The findings can be applied to mining design or support design in deep mining of high-gas-containing coal seam.

Bulk SiOC ceramics were prepared by spark plasma sintering of polymer-derived SiOC powders, and the effects of ion irradiation on their microstructures and properties were investigated in detail. High sintering temperature was conducive to low open porosity, high bulk density, nucleation and growth of β-SiC nanodomains, and graphitization of free carbon clusters in the SiOC ceramics. Ordering of the nanodomanins is beneficial for improving hardness and modulus of the ceramics. After 70 keV He ion irradiations, the β-SiC nanocrystals and graphitic clusters were partially amorphized, and their average grain size decreased by 13.6% and 50.9%, respectively. But no bubbling or peeling occurred on the irradiated sample surface, the hardness and modulus barely changed, indicating the SiOC ceramics are promising as radiation-tolerant materials.

Teaching–learning-based optimization (TLBO) has been widely used to solve global optimization problems. However, the optimization problems in various fields are becoming more and more complex. The canonical TLBO is easy to be trapped in the local optimum when dealing with these problems. In this paper, a new TLBO algorithm with collective intelligence concept introduced is proposed, namely collective information-based TLBO (CIBTLBO). CIBTLBO uses the information from the top learners to form CITeachers and uses the neighborhood information of each learner to form NTeachers, and these teachers help other learners learn in the teacher phase. Furthermore, CITeacher also helps in the learner phase. To demonstrate superiority of the proposed algorithm, experiments on 28 benchmark functions from CEC2013 are carried out, and the benchmark functions are set to 10, 30, 50 and 100 dimensions, respectively. The results show that the proposed CIBTLBO algorithm outperforms the other previous related algorithms.

A high-frequency magnetic field (MF) generates an electric current by charging conductors that enable the induction of various biological processes, including changes in cell fate and programming. In this study, we show that electromagnetized carbon porous nanocookies (NCs) under MF treatment facilitate magnetoelectric conversion for growth factor release and cell stimulation to induce neuron cell differentiation and proliferation in vitro and in vivo. Integrating four-dimensional printing technology, the NCs are exposed on the surface, which enhances the cell adhesion and allows direct manipulation of electromagnetic stimulation of the cells. Remarkably, large amounts of growth factor encapsulated in NC@conduit resulted in excellent permeability and on-demand release, improving the in vivo layers of myelin sheaths and directing the axon orientation at 1 month postimplantation. This study offers proof of principle for MF-guided in vivo neuron regeneration as a potentially viable tissue regeneration approach for neuronal diseases. Researchers in Taiwan have developed a printable biomaterial that has potential for neuron regeneration and treating neural diseases. Four-dimensional printed materials are objects created using 3D printing technology but whose properties can be altered in time, by electrical pulses for example. A team led by San-Yuan Chen from National Chiao Tung University and Shang-Hsiu Hu from National Tsing Hua University, both in Hsinchu, made biomedical four-dimensional printed material by combining stretchable and biocompatible graphene oxide nanosheets with so-called nanocookies: porous carbon with silica embedded into its surface. The pores in the carbon act as a scaffold on which neurons can grow, and an electric current induced in the silica by a high-frequency magnetic field stimulated this growth. The team observed this stimulation in both cell cultures and rat models. 4D Printing Conduits: Electromagnitized carbon porous nanoccookies (NCs) under MF facilitate magneto-electrical conversion for growth factor release and cell simulation. Integrating four-dimensional (4D) printed technology, exposed NCs are able to enhances the cell adhesion and manifest directly electromagnetic stimulation to cells.

Volatile organic compounds (VOCs) from polypropylene (PP) seriously restricts the application of PP in an automotive field. Herein, the traceability of VOCs from PP resins during manufacturing process and accelerated photoaging degradation was clarified on basis of an accurate characterization method of key VOCs. The influence of PP structures on changing the accelerated photoaging degradation on the VOCs was systematic. The VOCs were identified by means of Gas chromatography (GC) coupled with both a hydrogen flame ion detector (FID) and a mass spectrometry detector (MSD). Results showed that both the molecular structure of PP and the manufacturing process affected the species and contents of VOCs. In addition, the photoaging degradation of PP resulted in a large number of new emerged volatile carbonyl compounds. Our work proposed a possible VOC formation mechanism during the manufacturing and photoaging process. VOCs from PP resins were originated from oligomers and chain random scission during thermomechanical degradation. However, &beta, scission of alkoxy radical and Norrish tape I reactions of ketones via intermediate transition were probably the main VOCs formation routes towards PP during photoaging degradation. This work could provide scientific knowledge on both the accurate traceability of VOCs emissions and new technology for development of low-VOCs PP composites for vehicle.

Microseismic (MS) source location is a fundamental and critical task in mine MS monitoring. The traditional ray tracing-based location method can be easily affected by many factors, such as multi-ray path effects, waveform focusing and defocusing of wavefield propagation, and low picking precision of seismic phase arrival. By contrast, the Gaussian beam reverse-time migration (GBRTM) location method can effectively and correctly model the influences of multi-path effects and wavefield focusing and defocusing in complex 3D media, and it takes advantages of the maximum energy focusing point as the source location with the autocorrelation imaging condition, which drastically reduces the requirements of signal-to-noise ratio (SNR) and picking accuracy of P-wave arrival. The Gaussian beam technique has been successfully applied in locating natural earthquake events and hydraulic fracturing-induced MS events in one-dimensional (1D) or simple two-dimensional (2D) velocity models. The novelty of this study is that we attempted to introduce the GBRTM technique into a mine MS event location application and considered utilizing a high-resolution tomographic 3D velocity model for wavefield back propagation. Firstly, in the synthetic test, the GBRTM location results using the correct 2D velocity model and different homogeneous velocity models are compared to show the importance of velocity model accuracy. Then, it was applied and verified by eight location premeasured blasting events. The synthetic results show that the spectrum characteristics of the recorded blasting waveforms are more complicated than those generated by the ideal Ricker wavelet, which provides a pragmatic way to evaluate the effectiveness and robustness of the MS event location method. The GBRTM location method does not need a highly accurate picking of phase arrival, just a simple detection criterion that the first arrival waveform can meet the windowing requirements of wavefield back propagation, which is beneficial for highly accurate and automatic MS event location. The GBRTM location accuracy using an appropriate 3D velocity model is much higher than that of using a homogeneous or 1D velocity model, emphasizing that a high-resolution velocity model is very critical to the GBRTM location method. The average location error of the GBRTM location method for the eight blasting events is just 17.0 m, which is better than that of the ray tracing method using the same 3D velocity model (26.2 m).

The refrigerant circulation heat can be enhanced through the mutual transformation between thermal energy and surface energy during the adsorption and separation process of fluid molecules in porous materials. In this paper, the adsorption and energy storage of R1234ze(z), R1234yf, R32 and R134a, as well as their mixed refrigerants in Mg-MOF-74 and Ni-MOF-74 nanoparticles were investigated by means of molecular dynamics simulations and grand canonical Monte Carlo simulations. The results suggested that, in the case of pure refrigerant adsorption, the adsorption quantities of R32 and R134a in MOFs were higher than those of R1234yf and R1234ze(z). However, in the case of saturation adsorption, the desorption heat of R32 was lower than that of R1234yf and R1234ze(z). The addition of MOF-74 nanoparticles (NPs) could enhance the energy storage capacity of the pure refrigerant; besides, R1234yf and R1234ze(z) nanofluids had superior enhancement effect to that of R32 nanofluid. In mixed refrigerant adsorption, the adsorption quantities of R1234ze(z) and R1234yf were lower than those of R32 and R134a; with the increase in temperature, the adsorption of R1234ze(z) and R1234yf showed a gradually increasing trend, while that of R32 was gradually decreased.

The poor impermeability of fractured rock induced by excavation and construction is improved through the application of microbial-induced calcite precipitation (MICP), but it is difficult to monitor and evaluate the permeability reduction under a confining pressure and fracture aperture. For this, the grouting ratio, permeability, and electrochemical impedance of fractured rock with MICP grouting were experimented with, considering the effects of fracture aperture and confining pressure. The equivalent circuit model of grouting-fractured rock is presented, and the corresponding ratio of the electrical resistivity and cross-sectional area of the grouted fracture ( ρ / S ) is indicated by an electrochemical impedance spectroscope (EIS). The relationships of the permeability coefficient, the ρ / S , and the grouting ratio are analysed. The experimental results show that the Darcy permeability coefficient of fractured rock with MICP grouting is reduced by an order of magnitude of 3 to 4. As fracture aperture ranged from 1.28 to 2.56 mm and grouting rate was 0.003 ml/s, the Darcy permeability coefficient decreased with an increase in confining pressure. The grouting ratio and fracture aperture also decreased with a reduction in ρ / S . The results also showed that the permeability reduction of MICP correspondingly increased in these conditions. What is more, the Darcy permeability coefficient of fractured rock grouted by MICP and its permeability reduction may be well predicted by confining pressure and ρ / S . This study provides a new EIS method for predicting the reduction in permeability of MICP grouting-fractured rock and further enriches the application of MICP and EIS techniques in impermeable rock engineering.

Geotechnical properties of red shale encountered in deep underground mining were characterized on both laboratory and field scale to reveal its unfavorably in geoenvironment. Its constituents, microstructure, strength properties and water-weakening properties were investigated. In situ stress environment and mining-induced fractured damage zone after excavation were studied to reveal the instability mechanism. The results show that red shale contains swelling and loose clayey minerals as interstitial filling material, producing low shear strength of microstructure and making it vulnerable to water. Macroscopically, a U-shaped curve of uniaxial compressive strength (UCS) exists with the increase of the angle between macro weakness plane and the horizon. However, its tensile strength reduced monotonically with this angle. While immersed in water for 72 h, its UCS reduced by 91.9% comparing to the natural state. Field sonic tests reveal that an asymmetrical geometrical profile of fractured damage zone of gateroad was identified due to geological bedding plane and detailed gateroad layout with regards to the direction of major principle stress. Therefore, red shale is a kind of engineering soft rock. For ground control in underground mining or similar applications, water inflow within several hours of excavation must strictly be prevented and energy adsorbing rock bolt is recommended, especially in large deformation part of gateroad.

A spatial confinement effect of CdS nanoparticles in mesoporous alumina, which is synthesized through evaporation-induced self-assembly (EISA) method, post-impregnation approach and microwave irradiation process, was investigated to verify the enhanced catalytic activity and stability with less aggregation of CdS crystallites during decoloration of organic dyes under visible-light irradiation. In this work, we utilize inexpensive natural clays for preparing mesoporous alumina via evaporation-induced self-assembly method, and used as the host for confining CdS nanoparticles to suppress the crystallite growth and aggregation. The loading amount and grain size of CdS nanoparticles significantly altered catalytic activity and stability. CdS clusters confined inside the mesoporous channels provided abundant reactive sites for photocatalytic reaction through spatial confinement effect, quantum size effect and sulfide-support interaction, thus greatly enhancing the reaction activity. CdS/MAl composites have large special surface area, strong visible light absorption and high quantum yields. CdS/MAl-25 photocatalyst has exhibited remarkably enhanced visible light photoactivities as compared to other catalysts, and the overall decoloration rate was up to 97.5% after visible light irradiation for 60 min. The CdS/MAl composites exhibit potential applications in the wastewater treatment under visible light irradiation.

MoS2 nanosheet/palygorskite nanofiber (MoS2/Pal) hybrid nanostructures were synthesized via facile hydrothermal method, and the catalytic activities of samples were assessed by reduction of 4-nitrophenol (4-NP). The structure characterizations indicate that the MoS2 nanosheets with abundant active sites are assembled on the palygorskite (Pal) nanofiber, and the Pal could prevent MoS2 nanosheets aggregation. With MoS2/Pal as catalyst, the decoloration rate of 4-NP reaches up to 99.72% after 10 min, and the apparent reaction rate constant is 0.750 min−1 at catalyst concentration of 1.0 g/L. The MoS2/Pal exhibits higher catalytic activity than hydrothermally synthesized MoS2 for the reduction reaction of 4-NP, which could be attributed to the synergistic effect of more reactive sites in hybrid nanostructures and the hydrophilicity of Pal. The as-prepared MoS2/Pal hybrid nanostructures are promising candidates for catalytic applications in the water-treatment and biomedical fields. The synthesis process and catalysis mechanism of MoS2/Pal were explored, which might provide insights for designing high activity and cost-effective catalysts.

Double network (DN) hydrogels as one kind of tough gels have attracted extensive attention for their potential applications in biomedical and load-bearing fields. Herein, we import more functions like shape memory into the conventional tough DN hydrogel system. We synthesize the PEG-PDAC/P(AAm-co-AAc) DN hydrogels, of which the first network is a well-defined PEG (polyethylene glycol) network loaded with PDAC (poly(acryloyloxyethyltrimethyl ammonium chloride)) strands, while the second network is formed by copolymerizing AAm (acrylamide) with AAc (acrylic acid) and cross-linker MBAA (N, N'-methylenebisacrylamide). The PEG-PDAC/P(AAm-co-AAc) DN gels exhibits high mechanical strength. The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m3, respectively. Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network, the PEG-PDAC/P(AAm-coAAc) DN hydrogels use P(AAm-co-AAc), a weak polyelectrolyte, as the second network. The AAc units serve as the coordination points with Fe3+ ions and physically crosslink the second network, which realizes the shape memory property activated by the reducing ability of ascorbic acid. Our results indicate that the high mechanical strength and shape memory properties, probably the two most important characters related to the potential application of the hydrogels, can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.

This study focused on heat-affected zone thermal processes, microstructural evolution, and impact toughness near weld toe of backing passes in double-sided double arc welding where there is stress concentration. The results show that as the arc distance increases, the second peak temperature near weld toe will accordingly decrease and the intercritically reheated coarse-grained heat-affected zone will appear. The formation of martensite-austenite constituents distributed both along the prior austenite grain boundaries and inside prior austenite grains leads to the poor toughness of intercritically reheated heat-affected zone. When short arc distance is adopted, supercritically reheated coarse-grained heat-affected zone will appear near weld toe which possesses high toughness due to the good toughness of lath bainite and the fine bainite/martensite packets. During double-sided double arc backing welding, short arc distance should be used to obtain excellent impact toughness.

The acidity enhancement induced by the nonpolar solvent effect of naphthalene inside zeolites was unambiguously identified. The mechanism of such an effect due to the CH/π interaction in the nonpolar environment has been revealed based on the advanced 2D 1H-13C correlation NMR technique and DFT calculations for the first time.

Integrating distinct environmental responsive behaviors into polymer fluids is an enormous challenge. Herein we report an intelligent electrothermal rheological fluid exhibiting two remarkably different temperature responsive rheological behaviors, thermothinning versus thermogelling, which are controlled by voltage. By virtue of a cyclodextrin-based host–guest interaction, traditional responseless amphiphilic polymer solutions without LCST features can be endowed with fascinating thermoreversible gelation abilities. By further introducing a competitive guest, the transduction of two independent signals (temperature and electrochemical stimuli) was achieved and the dynamic rheological properties can be varied over three orders of magnitude. This work should merit the design of cascade or logical gate materials using supramolecular interactions.

As one of the most promising biomaterials, injectable self-healing hydrogels have found broad applications in a number of fields such as local drug delivery. However, controlled release of drugs in hydrogels is still difficult to realize up to now. Here, we report a novel photo-degradable injectable self-healing hydrogel based on the hydrophobic interaction of a biocompatible four-arms star polymer, poly(ethylene glycol)-b-poly(γ-o-nitrobenzyl-l-glutamate). The hydrophobic interaction between poly(γ-o-nitrobenzyl-l-glutamate) not only connects poly(ethylene glycol)-b-poly(γ-o-nitrobenzyl-l-glutamate) together with a crosslink but also provides a hydrophobic domain to encapsulate hydrophobic pharmaceuticals such as doxorubicin (DOX). Due to the dynamic character of the hydrophobic interaction, the hydrogel exhibits excellent injectable and self-healing ability. In particular, the photolabile o-nitribenzyl ester group is cleaved under UV irradiation. As a result, the hydrophobic domain transforms into the hydrophilic one and the embedded DOX is released effectively. An increasing release ratio of DOX dramatically enhances the apoptosis ratio of HeLa cells. We expect these attractive properties may be beneficial to practical applications of the hydrogel as an effective local drug delivery means in a truly physiological environment.

The detection of mycotoxins in food is urgently needed because they pose a significant threat to public health. In this study, we developed a quantitative detection platform for mycotoxins by integrating multicolor upconversion nanoparticle barcode technology with fluorescence image processing using a smartphone-based portable device. The multi-colored upconversion nanoparticle encoded microspheres (UCNMs) were used as encoded signals for detecting different mycotoxins simultaneously. After indirect competitive immunoassays using UCNMs, images could be captured by the portable device and the camera of a smartphone. Then, a self-written Android application, which is an HSV-based image recognition program installed on a smartphone, analyzed images and offered a reliable and accurate result in less than 1 min. The quantitative detection platform of mycotoxins proved to be feasible and reliable, and the limit of detection (LOD) was 1 ng, which was lower than that obtained from standard assays. This study demonstrates a method for detecting mycotoxins in food and other point of care analysis.

This paper aims to reveal the influence of different welding conditions on unaltered coarse grained heat affected zones (UACGHAZs) of backing passes by double-sided double gas tungsten arc welding (DSGTAW) of 10CrNi3MoV steel. UACGHAZs were also compared with coarse grained heat affected zones (GGHAZs) of single gas tungsten arc welding (SGTAW). At lower heat input (21.7 kJ/cm for each run without preheating), CGHAZ mainly consisted of lath martensite (LM) while UACGHAZs composed of LM and small amount of lath bainite (LB). At higher heat input (33.2 kJ/cm for each run with 150 °C preheating), the microstructures of CGHAZ were LM and LB. In UACGHAZs, the microstructures would transform from LB + LM + granular bainite (GB) to LB + GB as arc distance (d) decreased. The toughness of UACGHAZs was related to martensite/bainite packet sizes instead of prior austenite grain sizes. At higher heat input, the formation of granular bainite deteriorated the toughness of UACGHAZs and negated the positive effect of LB on toughness. DSGTAW can significantly improve the toughness of coarse grained zones when lower heat input is adopted.

The low-temperature NO decomposition with high efficiency remains a grand challenge. Herein, we report an attractive approach for the low-temperature NO decomposition by microwave catalysis over BaMnO 3 and substituted Ba 0.8 A 0.2 MnO 3 (A Ca, K, La) catalysts. Importantly, impressively high NO conversion and N 2 selectivity with 99.9% and 99.9%, respectively, were achieved over Ba 0.8 K 0.2 MnO 3 catalyst at 250 °C. Comparatively, under identical conditions in the conventional reaction mode, the highest NO conversion and N 2 yield are respectively only 45.4% and 28.7% for Ba 0.8 K 0.2 MnO 3 at 650 °C. Unexpectedly, the effect of Ca, K and La substitution is different in these two reaction modes. The catalysts were characterized by H 2 -TPR, O 2 -TPD, and microwave absorbing properties to illustrate possible reasons causing such obvious differences in catalytic performance. The apparent activation energies for BaMnO 3 , Ba 0.8 Ca 0.2 MnO 3 , Ba 0.8 K 0.2 MnO 3 and Ba 0.8 La 0.2 MnO 3 catalysts under microwave irradiation drop down to as low as 33.4, 41.6, 14.7 and 18.2 kJ/mol, separately, suggesting a significant microwave catalytic effect.

Optimization of sound absorbing coefficient of porous copper under a limited dimension is focus of research in the fields of acoustics and mechanics. Through measuring the sound absorbing coefficient based on the standing wave method, 5 groups of experiments are conducted to investigate the sound absorbing property of the porous copper with cavity under a limited dimension of 30mm. There are two options can meet the requirement that the sound absorbing coefficients are larger than 70% in 2000-5000Hz. First is the pure porous copper with thickness of 30mm, and the other is the combination of porous copper with thickness of 25mm and cavity with thickness of 5mm. Based on the modified Johnson-Allard model with correction factor, it can be obtained that theoretical optimal thickness of the pure porous copper is 28.8mm, and the theoretical optimal combination of porous copper and cavity are 22.7mm and 7.3mm. Experimental validations indicate that the two optimal options of the two modes both can meet the sound absorbing requirement. The results will promote the application of porous copper and improve the sound absorbing theory of porous material. Keywords: Porous copper, Sound absorbing coefficient, Cavity, Modified Johnson-Allard model, Correction factor, Optimization

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield., Bio-oil is a potential major source of renewable fuels and chemicals. Here, the authors report a palladium-molybdenum mixed catalyst for the selective hydrodeoxygenation of water-insoluble bio-oil to mixtures of alkanes with high carbon yield.

In this study, the formation of granular bainite (GB) which may form in the heat-affected zone of double-sided double arc welding joint was in situ observed. The crystallographic characteristics of GB were also compared with those of microstructure mainly comprising lath bainite (LB). The results show that bainite packets exist at the initial stage of GB transformation and can be distinguished by the distribution of retained austenite and martensite–austenite constituents. The bainite blocks of GB are larger than those of LB which makes both the length and fraction of high-angle grain boundaries in GB less than those of LB which partly lead to the brittleness of granular bainite.

Activated carbon (AC) supported ceria and mixed metal oxides MeOx–CeO2 (Me = Ni, Mn, Fe) were investigated for microwave irradiation-selective catalytic reduction (MW-SCR) of NO in the microwave catalytic reaction mode (MCRM). NO conversion almost reached 100% for 5% (21% NiOx)-CeO2/AC at 300 °C, 5% (21% MeOx)-CeO2/AC (Me = Mn, Fe) and 5% CeO2/AC at 350 °C in the MCRM. The temperature of NO removal by SCR using AC as reductant in the MCRM was usually lowers 150–200 °C than that of in the conventional reaction mode (CRM). These results suggested that microwave irradiation could efficiently improve the activity of NO removal at low temperature and decrease the reaction temperature of NO with AC. MW-SCR of NO by AC primarily produced N2 and CO2, and O2 existence had no influence on the activity of NO removal by AC in the MCRM. These results show that microwave irradiation exhibit the microwave catalytic effect and microwave selective effect. This method of MW-SCR is a viable and promising method for flue-gas...

Thermal cycles of heat-affected zones (HAZs) in double-sided double arc welding (DSDAW) were measured in this study. The microstructure and impact toughness of specimens imposing typical thermal cycles of coarse-grained heat-affected zone (CGHAZ) were analysed by using thermal simulation. The results show that the two arcs influenced each other even during the deposition of the fourth layer in each side. Both of the two arcs could reduce the cooling rate of HAZs. Besides, the heating of the rear arc may make HAZ sustain in bainite transformation interval for a long time and lead to the formation of granular bainite which could deteriorate welding joint. To obtain good toughness of joint by DSDAW, the arc distance during filling pass depositing should be properly enlarged to eliminate granular baintie under the premise that the trough temperature (T t) is higher than 200 °C.

Despite a variety of T1-T2 dual-modal contrast agents (DMCAs) reported for magnetic resonance imaging (MRI), no tuning of local induced magnetic field strength of an DMCA, which is important to modulate the overall T1 and T2 responses for imaging delicate cells, tissues, and organs, is yet available. Here, we show that a spatial arrangement of T1 and T2 components within a "nano zone" in a single core-shell nanoparticle carrier (i.e., DMCA with core Fe3O4 and MnO clusters in a silica shell) to produce the necessary fine-tuning effect. It is demonstrated that this particle after the anti-CD133 antibody immobilization allows both T1 and T2 imaging at higher resolution for living ependynmal brain cells of rodents with no local damage under a strong MRI magnetic field. This study opens a route to rational engineering of DMCAs for accurate magnetic manipulations in a safe manner.

The failure mode of rock under cutting exhibits a ductile-brittle transition as the depth of cut increases. The critical transition depth, beyond which energy consumed in brittle fracturing surpasses the energy consumed in plastic flow, is the key to differentiating between the ductile and brittle cutting modes and therefore is an important parameter to optimise tool design and operational parameters to meet specific application requirements. This critical failure mode transition depth depends not only on rock properties but also on cutting operational parameters, in particular, the back rake angle. In this work, a series of rock cutting tests were performed to investigate the influence of back rake angle on the critical failure mode transition depth. Size effect law is employed first to identify the critical transition depths, which are then compared with values derived from the analysis of specific cutting energy. It is found that the critical failure mode transition depth increases with the back rake angle. This suggests that the brittle fracture failure induced at large depth of cut can be inhibited by increasing the back rake angle. Cutting at a small back rake angle, on the other hand, is desirable if minimisation of the cutting energy is required in the application.

In order to obtain an efficient phase change material (PCM), emerging montmorillonite/stearic acid (Mt/SA) microcapsules containing SA core with Mt shell were designed and prepared via self-assembly of Mt in the SA emulsion. The Mt/SA microcapsules were coated with SiO 2 from the hydrolysis and polycondensation of TEOS to enhance the structure stability. The microstructure, thermal properties and reliability of Mt/SA microcapsules were investigated via scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The Mt/SA microcapsules presented sphere-like particles and had a size distribution from 10 to 30 μm. The freezing latent heat of the Mt/SA microcapsules was 118 J/g at 52.3 °C. The energy storage rate of the Mt/SA microcapsules was faster compared to SA. The Mt/SA microcapsules had excellent structural stability, high energy storage capacity and stable energy storage and release performances. The energy storage performances of the Mt/SA microcapsules were superior to the Mt/SA composites prepared via vacuum impregnation. Excellent energy storage reliability and capability of the Mt/SA microcapsules have advantages for solar energy storage fields.

CO2-responsive hydrogels, using CO2 as a “green” trigger, have recently been of considerable interest. Herein, a novel CO2-responsive self-healable hydrogel is fabricated by simply mixing hydrophobically modified polyacrylamide (HMPAM) with sodium dodecyl sulfate (SDS)–N,N,N′,N′-tetramethyl-1,3-propanediamine (TMPDA) surfactant micelles. In the presence of CO2, the SDS–TMPDA spherical micelles transform into long wormlike micelles, serving as multivalent cross-linkages to bridge HMPAM chains based on hydrophobic interactions. The interpenetrating three-dimensional network induces a sol-to-gel transition, accompanied by a 360 and 400 times enhancement of the zero-shear viscosity and storage modulus, G′ (ω = 6.28 rad s−1), respectively. In additon, the sol–gel transition can be repeatedly and reversibly switched by cyclically bubbling and removing CO2 without any harm. Furthermore, the CO2-responsive hydrogel exhibits significant shear-thinning and self-healing properties, suggesting that the hydrogel is injectable and could be used as a potential plug to block CO2 gas breakthrough channels during CO2 flooding. Therefore, we believe that the presented work will enable the development of the design of CO2-responsive self-healable hydrogels and their practical applications.

The biped-wheel unmanned platform has the obvious advantages of high flexibility, high maneuverability, well controllability, great promptitude, fine adjustability, and a low manufacturing cost. A novel structure of the walking device of a biped-wheel platform has been investigated in this study, which is similar to the structure of airplane undercarriage. The structure is a plane four-bar linkage mechanism, which is composed of a side link, a connecting rod, a bracket, and a hand-spike. Swing range of the walking device determines the obstacle-surmounting capacity of biped-wheel unmanned platform. Therefore, the swing range of the modified novel walking device is calculated through theoretical derivation. Afterwards, the obstacle-surmounting capacities of the biped-wheel unmanned platform, including the ditch-crossing and the stair-climbing, are investigated based on the kinematic and kinetic analysis. Relative to the common type, reliability of the modified walking device can be improved. The research would increase the development level of the biped-wheel unmanned platform and promote its application in military and industrial fields.