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Three types of radical–3d/3d–4f heterotrispin complexes have been obtained. The Tb derivative reveals slow magnetic relaxation and a selective luminescent probe coexisting in a molecular entity.

Cloud computing and edge computing have potent capabilities and value, and the combination of edge computing and wireless transmission has become a research hotspot, making cloud computing and edge computing adapt to broader application scenarios and exert more powerful functions. Due to the relatively large data volume of terminal devices in the edge computing network, how to process the upstream data stream and efficiently and accurately realize the wireless data monitoring transmission is a problem that the edge server needs to solve. This paper analyzes the interaction and cooperation relationship between levels, proposes a scheduling model and storage strategy for uplink data flow, and uses data flow scheduling and data flow hierarchical storage algorithms to optimize the edge system of data flow scheduling and storage. Combined with the attributes of the edge computing network system, the measurement indicators of the scheduling and storage of the terminal uplink data flow in the edge computing network are modeled and analyzed. We analyze the processing time delay, cost, and optimization target for optimizing the data transmission task. The simulation experiments prove that the algorithm in this paper has advantages in solving data transmission and storage problems in the network. It can reduce costs and delays, increase throughput, ensure monitoring node access delays, and maintain edge servers and disaster monitoring data centers.

The rock of weakly consolidated coal measure strata has the characteristics of low mechanical strength and strong water sensitivity. Under the stress and seepage disturbance caused by coal seam mining, the surrounding rock structure is prone to instability, which leads to mine safety accidents and water resources loss. In order to master the mechanical response and permeability evolution law of weakly consolidated rock under the disturbance of coal seam mining, the specimens of Jurassic mudstone, sandy mudstone, and sandstone in the Ili mining area of China were collected, and a triaxial compression seepage test was carried out. A comprehensive analysis was carried out on the mineral composition and microstructure characteristics of the rock. The results show the following: (1) Compared to the constant confining pressure condition, mining-induced stress promotes the fracture development rate of weakly consolidated rocks. The ratios of strain at the yield point of mudstone, sandy mudstone, and sandstone under mining-induced stress and constant confining pressure are 0.33, 0.43, and 0.79, respectively, and the ratios of strain at the failure point were 0.48, 0.52, and 0.72, respectively. (2) Under the condition of mining-induced stress, the permeability change range and the permeability recovery rate of the three types of rocks were different, which decreased in the order of mudstone, sandy mudstone, and sandstone. (3) In the process of the triaxial compression test, there was a strong hysteresis in the permeability change of the mudstone, and the permeability and hysteresis of the three types of rocks decreased with the increase in the clay mineral content. (4) Combined with the analysis of the rock mineral composition and microstructure characteristics, it is believed that the clay minerals in the rock after water mud and swelling are the main reasons for the hysteresis of the permeability change of weakly consolidated rock, and the content of clay minerals is the main factor affecting the permeability characteristics of the weakly consolidated rock.

Shale is classified as a poroelastic material as the shale matrix has comparable stiffness with its constituent solid grains. Also, shales at large depth are often fully saturated. Due to their low permeability, which can be in the nano-Darcy range, shales remain undrained during typical loading conditions. Additionally, shales are quasi-brittle materials which can exhibit very pronounced peak shear stress followed by pronounced strain softening during shearing. All these unique aspects of shale behavior must be considered in developing a model that predicts the change of the pore pressure, the effective stress response and the undrained shear strength of shales during loading. This study presents a coupled plastic-damage constitutive model which considers poroelastic effect with the objective to predict the mechanical behavior of saturated shales under undrained condition. The proposed model couples the plastic mechanism, which is formulated on the effective stress space, and the damage mechanism which is responsible for the elasticity degradation and the post-peak softening of shale. Validation of the proposed model against triaxial est results demonstrates that the proposed model can predict the stress-strain behavior, the effective stress path and the pore pressure evolution of shale specimen during shearing.

Implementing coal to synthetic natural gas (SNG) is a key way to deal with the conflict between supply and demand of natural gas in China. For the coal to SNG process, gasification is a crucial unit, which determines the syngas composition and influences cost of coal to SNG system. In this current study, a coal to SNG system using ash agglomerating fluidized bed gasification is designed and modeled. According to the above results, the thermal performance and technoeconomic assessment of the coal to SNG system are performed. The research demonstrates that exergy efficiency and energy efficiency of the whole system are 55.37% and 61.50%, respectively. Additionally, the results of the economic evaluation show that the SNG production cost is 1.87 CNY/Nm3 with a coal price of 250 CNY/t and an electricity price of 0.65 CNY/kWh. Sensitivities to variables such as water price, electricity price, total equipment cost and coal price are performed. Coal price represents the most important sensitivity, but the sensitivity to water price is relatively small.

Shales play important roles in various civil, energy and environmental engineering applications. Shales are categorized as poroelastic materials due to their tight and very stiff structure, and reliable poroelastic properties are required when dealing with shales. This paper presents simple procedures to determine the poroelastic properties of rocks using oedometer and triaxial consolidation tests. The procedures, which avoid the difficulty to perform determination of the unjacketed bulk modulus of the rock minerals, are demonstrated on a North Sea shale. The experimentally obtained Biot coefficient α and the drained bulk modulus K of the shale range from 0.95 to 0.99, and from 0.17 to 2.00 GPa, respectively. The Biot coefficient α and the drained bulk modulus K values determined from the oedometer and triaxial tests are compared and show good agreement and consistency between the two test procedures. The Skempton’s coefficient B-value of the triaxial samples was also experimentally measured prior to the triaxial consolidation tests. The theoretically predicted B-value varies from 0.81 to 0.96 which is, on the average, only about 10% higher than the experimentally obtained B-value which range from 0.80 to 0.85.

A series of one-dimensional lanthanide chains [Ln(hfac)3(NITPh(4-NIT))]n (Ln(III) = Y 1, Gd 2, Tb 3 and Dy 4, hfac = hexafluoroacetylacetonate; NITPh(4-NIT) = 1,4-bis-(l′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-dihydro-1H-imidazol-2′-yl) benzene) based on a nitronyl nitroxide biradical ligand (NITPh(4-NIT)) has been successfully achieved and characterized. The NITPh(4-NIT) biradicals bridged Ln(hfac)3 units through their NO groups of two mono-radicals to develop a one-dimensional chain with a ‘zig-zag’ motif. Magnetic investigation shows that within the biradical ligand, two unpaired electrons are delocalized and expected to be antiferromagnetically coupled. The magnetic behavior of complexes have been analyzed by using an appropriate magnetic model with antiferromagnetic [Ln–biradical] moieties. Moreover, the Tb complex reveals field induced slow magnetic relaxation, arising from the SIM behavior of the Tb(III) center ion.

Water is crucial for biofuel production. It is important to study the influence of biofuel technology on water resource for the development of biofuel. Life cycle water footprint for the syngas production via chemical looping gasification of corn straw and wheat straw is developed in this paper. The results show that the total water consumption of syngas production via corn straw and wheat straw chemical looping gasification are 1139.84 and 2170.41 L H2O/m3 syngas, respectively. The total water consumption of the aforementioned approaches is both dominated by crop growth stage. Additionally, different allocation methods have significant impact on the total water consumption. Sensitivity analysis demonstrates that water consumption of crop yield and crop growth can have an almost same but opposite impact on water consumption efficiency. Based on the results, guidance can be provided for crop straw to syngas via chemical looping gasification to lower water use.

Photoactuators have attracted significant interest for soft robot and gripper applications, yet most of them rely on free-space illumination, which requires a line-of-site low-loss optical path. While waveguide photoactuators can overcome this limitation, their actuating performances are fundamentally restricted by the nature of standard optical fibres. Herein, we demonstrated miniature photoactuators by embedding optical fibre taper in a polydimethylsiloxane/Au nanorod-graphene oxide photothermal film. The special geometric features of the taper endow the designed photoactuator with microscale active layer thickness, high energy density and optical coupling efficiency. Hence, our photoactuator show large bending angles (>270°), fast response (1.8 s for 180° bending), and low energy consumption (, Despite promising devices, waveguide photoactuators actuating performances have been fundamentally restricted by the nature of standard optical fibres. To overcome these challenges, authors propose an optical fibre taper-enabled waveguide photoactuator and show enhanced performance.

The strain rate-dependent mechanical behavior of shale is characterized using triaxial compression tests under a constant confining pressure of 50 MPa and axial strain rates $$\dot{\varepsilon }_{1}$$ ranging from 5 × 10−6 s−1 to 1 × 10−3 s−1. This study is conducted on the Longmaxi shale from Dayou in China, which is predominantly composed of brittle minerals including quartz (55%), albite (15%) and cristobalite (3%). The experimental results show that higher axial loading strain rates $$\dot{\varepsilon }_{1}$$ lead to higher elastic modulus and higher peak shear strength, both following exponential relationships with $$\dot{\varepsilon }_{1}$$ . When $$\dot{\varepsilon }_{1} \le 1 \times 10^{ - 5} {\text{s}}^{ - 1}$$ , failure results in a single linear fracture, whereas a more complex multiple crisscrossing fracture network is formed when $$\dot{\varepsilon }_{1} \ge 1 \times 10^{ - 4} {\text{s}}^{ - 1}$$ . Failure in shale specimens can be described by a damage parameter $$D$$ , which is strongly affected by the axial strain $$\varepsilon_{{1{\text{s}}}}$$ . In addition, the strain rate $$\dot{\varepsilon }_{1}$$ had different effects on $$D$$ , which also depends on axial strain $$\varepsilon_{{1{\text{s}}}}$$ . Energy accumulation and dissipation are also closely related to $$\dot{\varepsilon }_{1}$$ with the total absorbed energy $$U_{\text{A}}$$ , the recoverable elastic strain energy $$U_{\text{A}}^{\text{e}}$$ and the dissipated energy $$U_{\text{A}}^{\text{d}}$$ at the peak stress increasing with $$\dot{\varepsilon }_{1}$$ . As for the total energy accumulation $$U_{\text{A}}$$ , the recoverable elastic energy $$U_{\text{A}}^{\text{e}}$$ decreases while the dissipated energy $$U_{\text{A}}^{\text{d}}$$ increases with increasing strain rate.

The turn-back tunnel of Guangzhou Metro Line 3 Tianhe Station with a large span was excavated in sandy clay which may easily break and disintegrate. The artificial ground freezing (AGF) technique was used to stabilize the soil and to prevent its collapse during excavations. Most of the existing theoretical analysis and numerical simulation on the AGF technique are purely based on a couple of assumptions, which are not able to produce accurate predictions. It would be more accurate for the AGF analysis to include the field monitoring. In this study, the coupled method of the field monitoring, the analytical formula, and the numerical method is used to evaluate the thickness and average temperature of the frozen zone. Field monitoring was conducted to measure the temperature of the brine and the ground. Analytical formula was used to compute the thickness and the average temperature of the frozen zone. Numerical simulation is also carried out to predict the thickness and the temperature field of the frozen zone. According to the analytical and numerical analysis, the computed thickness and average temperature of the frozen zone meet the designed requirements of the project, which are further confirmed by the successful excavation of the tunnel. This indicates that the coupled method used in this paper is reliable and would be helpful for the AGF application in practical engineering.

In this paper, two standard physics-based compact models of GaN HEMTs, MVSG-RF and ASM-HEMT, are compared. The current voltage (I-V) output characteristics and capacitance voltage (C-V) characteristics of a depletion-mode GaN device with channel length of 0.25 µm, gate width of 125 µm and gate finger of 2 were simulated and compared with experimental data to verify the validity of the two models. From the results, it is observed that both MVSG and ASM accurately model the DC performances of the device, but the model precision of AC characteristics is still insufficient. Finally, Load-Pull simulation is carried out.

Water is essential in conversion of crop to bioenergy. Therefore, it is important to carefully evaluate the impact of bioenergy technology on water source. Life cycle water footprints of biobutanol from wheat straw, corn grain and corn stover are analyzed in this study according to the characteristics of crop growing and climate conditions. The results show that life cycle water footprints of biobutanol from wheat straw, corn grain and corn stover are 271, 108 and 240 L H2O/MJ biobutanol, respectively. Life cycle water footprints of the crop production stage for wheat straw, corn grain and corn stover are 269.89, 107.84 and 238.95 L H2O/MJ biobutanol, respectively. Owing to the use of fertilizer in the crop production stage, gray water footprint of wheat straw, corn grain and corn stover accounts for 91.08%, 86.65% and 86.40% of the life cycle water footprint, respectively.

In the current study, based on the national fire statistics from 2003 to 2017, we analyzed the 24-hour occurrence regularity of fire in China to study the occurrence regularity and influencing factors of fire and provide a reference for scientific and effective fire prevention. The results show that the frequency of fire is low from 0 to 6 at night, accounting for about 13.48%, but the death toll due to fire is relatively high, accounting for about 39.90%. Considering the strong seasonal characteristics of the time series of monthly fire frequency, the SARIMA model predicts the fire frequency. According to the characteristics of time series data and prediction results, an optimized Seasonal Autoregressive Integrated Moving Average Model (SARIMA) model based on Quantile outlier detection method and similar mean interpolation method is proposed, and finally, the optimal model is constructed as SARIMA (1,1,1) (1,1,1) 12 for prediction. The results show that: according to the optimized SARIMA model to predict the number of fires in 2018 and 2019, the root mean square error of the fitting results is 2826.93, which is less than that of the SARIMA model, indicating that the improved SARIMA model has a better fitting effect. The accuracy of the results is increased by 11.5%. These findings verified that the optimized SARIMA model is an effective improvement for the series with quantile outliers, and it is more suitable for the data prediction with seasonal characteristics. The research results can better mine the law of fire aggregation and provide theoretical support for fire prevention and control work of the fire department.

This paper proposes a physics-based analytical model for threshold voltage of p-GaN gate HEMT. Based on the EPFL HEMT model, the electric potential obtained by the Poisson’s equations is combined with the discontinuity of the interface displacement vector to get the analytical threshold voltage model, considering the total negative polarization induced charge density at the p-GaN/AlGaN interface and the Mg out-diffusion of the p-GaN gate layer. Additionally, the resulting threshold voltage transients are explained using technology computer-aided design (TCAD) simulations, and good results verify the correctness of our derivation.

A creep model based on the damage mechanics is proposed in this study to describe the three-stage creep deformation of rocks under conventional triaxial loading conditions. The proposed model has a simple form as it is based on the mechanism which assumes that the time-dependent creep behavior of rocks is solely described by the damage evolution. Verification of the proposed model against the creep tests shows that the model can reflect the three-stage creep behavior under higher stress levels as well as the elastic behavior under lower stress levels using the same model equations. The features of the proposed model include: (1) Simple mathematical form as it contains only one strain component without strain partitioning, and one set of equations to predict the creep deformation for all stress levels; and (2) The model requires only four parameters. All these features make the proposed model simple to use and easy to implement.

Shales are the most common materials on the Earth's surface that are frequently encountered in various energy, environmental, and engineering applications. Numerically predicting the mecha...

The roadways located in weak ground experience strong and cyclic dynamic loading induced by the thick coal seam extraction, which caused costly support and delay of normal production. This paper discusses the critical issues and support strategy for such roadways through a case study on a roof collapsed roadway which was excavated in a coal stratum at a depth of 120 m in Shanxi Province, China. A 2-m-high void between the concrete support and the exposed roof strata was left untreated due to poor roadway construction. The roadway collapse reached up to approximately 6 m in the roof strata, which was attributed to the large untreated void as well as the highly fractured rock mass. A combination support method of the void filling, the fracture grouting, and rock bolting was proposed to rebuild and reinforce the roadway. The deformation of the roadway was effectively controlled, and the maximum roof displacement reached 135 mm. The failure mechanism of the roadway was numerically investigated using discontinuous deformation analysis (DDA) based on specific geological conditions. The numerical findings suggested that the void above the roadway could significantly impact on the stability of the overlying strata.

Biomass chemical looping gasification (BCLG) is a promising gasification technology to convert biomass into synthesis gas with no need for molecular oxygen. In this study, a novel process for butanol production from lignocellulosic biomass based on BCLG is proposed. The proposed process is simulated using Aspen Plus and composed of main sub-processes such as BCLG, acid gas removal, synthesis and separation of alcohol. An economic assessment is conducted according to results of Aspen Plus model. The equipment cost for the proposed process is evaluated as 4.65 × 108 CNY and the minimum butanol selling price is estimated as 9.35 CNY/kg. Sensitivity analysis of the process indicates that pine sawdust price has the largest effect on the minimum butanol selling price followed by total equipment cost and plant lifetime. Finally, impacts of CO conversion and carbon tax on the minimum butanol selling price are explored.

Overlapped subway shield tunnels are subjected to the dynamic impacts caused by running trains and are damaged during their long-term service life. In this paper, the dynamic response and c...

The success of the water-preserved mining technology is closely related to the stability of the aquiclude and the aquifer, in particular, which is made of weakly cemented rock mas. This paper starts with the tri-axial compression tests on the mudstone specimens obtained from the Ili mining area, followed by the systematic numerical simulation via the Particle Flow Code (PFC) program, aiming at obtaining an in-depth understanding of the response of weakly cemented mudstone under tri-axial compression loading state. The main outcomes obtained from this research indicated that: (1) the behavior of weakly cemented mudstone is closely sensitive to the confining pressure. As the confining pressure increases, both the peak strength and plastic deformation capacity of weakly cemented mudstone will be enhanced; (2) the main feature of weakly cemented mudstone after tests is its centrosymmetric “Z” shape, mainly attributed to the progressive separation of the particle element of mudstone; (3) the behavior of weakly cemented mudstone either in terms of the axial stress-axial strain or the failure mode is sensitive to the confining pressure. If the applied confining pressure is lower than 5 MPa, the micro-cracks are in the form of the single shear band, whereas the tested specimens will tend from brittle shear to plastic shear associated with the “X” shear when the confining pressure is higher than 5 MPa; and (4) The failure of weakly cemented mudstone is mainly attributed to the continuous expansion and penetration of internal microcracks under compression. The brittle failure mode of weakly cemented mudstone tends to ductile failure with the increase of confining pressure. The main contribution of this research is believed to be beneficial in deepening the understanding of the mechanics of weakly cemented mudstone under tri-axial compression and providing the meaningful reference to the practical application of water-preserved mining in the Ili mining area.

The dynamic response of the overlapped shield tunnels subjected to the train-induced vibration is studied using a nonlinear finite element software. A three-dimensional numerical model is established, and the fabricated segment linings which contain steel bars are used to simulate the shield tunnel. The interaction behaviors, i.e., tensile, shear, and bending, between segment linings are successfully captured by defining the segment lining circumference interface and the joint bolt model. The results show that the dynamic response of the segment linings of the overlapped shield tunnels is affected by the vibration loads caused by the running trains. The additional internal forces generated in the shield tunnels with the fabricated segment linings (joint interfaces are explicitly represented) are larger than those of tunnels which use homogeneous equivalent stiffness model. The opening and staggered deformation response of the joint interfaces is related to the train locations. The axial force and shear response of the bolt under the dynamic load of the train are closely associated with the opening and staggered deformation of joints. The steel spring floating slab can greatly reduce the vertical acceleration and the displacement at the arch bottom of the lower tunnel. The vertical acceleration and the displacement of the bottom arch at the L-III segment lining with the steel spring floating plates are 0.65 times and 0.78 times of the tunnels without the steel spring floating plates, respectively. This study reveals the vibration response features of the overlapped shield tunnels under the train-induced vibration loads, which will help improve the waterproofing capacity and stability of shield tunnels.

This paper presents a numerical investigation of the effects of boundary conditions, i.e., constant normal load (CNL) and constant normal stiffness (CNS), on the failure mechanism of incipient rock discontinuities in direct shear. A series of numerical simulations were performed using the particle-based discrete element method (DEM), in which rock matrix and rock bridges (on incipient joint planes) were modeled as an assembly of rigid particles that were bonded together at their contacts. Smooth-joint model was assigned to particles of the persistent portions of incipient rock joints. Input micro-parameters of particles, bonds and smooth-joint were calibrated against a series of laboratory experiments. The study reveals that CNL and CNS boundary conditions significantly affect shear characteristics of incipient rock discontinuities. Peak shear stress increased significantly (up to three times) in the CNS direct shear in comparison with that measured in the CNL direct shear under the same initially applied normal stresses. The significant increase of shear stress in the CNS direct shear tests conducted in this study was related to the opening of newly created micro-cracks and creation of the rupture zones within the rock bridges, leading to a dramatic increase in the normal stresses. In the meanwhile, yield behavior was observed in the CNS direct shear while brittle failure was noticed in the CNL direct shear. It is also found that micro-cracks initiated at the vicinity of rock bridges in both CNL and CNS shear tests, while they propagated differently due to the gradual increase of normal stress under CNS boundary conditions.

This paper proposes a WD-GA-LSSVM model for predicting the displacement of a deep-seated landslide triggered by seasonal rainfall, in which wavelet denoising (WD) is used in displacement time series of landslide to eliminate the GPS observation noise in the original data, and genetic algorithm (GA) is applied to obtain optimal parameters of least squares support vector machines (LSSVM) model. The model is first trained and then evaluated by using data from a gentle dipping (~2°-5°) landslide triggered by seasonal rainfall in the southwest of China. Performance comparisons of WD-GA-LSSVM model with Back Propagation Neural Network (BPNN) model and LSSVM are presented, individually. The results indicate that the adoption of WD-GA-LSSVM model significantly improves the robustness and accuracy of the displacement prediction and it provides a powerful technique for predicting the displacement of a rainfall-triggered landslide.

In recent years, the rainstorm and flood disasters frequently happened in cities and posed increasingly wide challenges. Therefore, the whole development process of urban rainstorm and flood disaster should be carried out for the reasonable and quantitative assessment on cities' ability to respond to rainstorm and flood disasters, and the index system of risk assessment on regional flood disaster is constructed based on the three attributes of vulnerability, adaptability and restorability. 3 first-class and 14 s-class indexes are set up accordingly. The weight of each index is calculated by weighting methods which are both subjective and objective based on entropy-weight order relation. Then, the theoretical model for risk assessment is established by weighted clustering assessment. Finally, the empirical analysis was conducted on the current situation of rainstorm and flood disaster in 8 regions of a city in China. The results show that among the risk grade of rainstorm and flood disaster in 8 regions, there are 2 regions with grade-II higher risk, 5 regions with grade-III general risk and 1 region with grade-IV low risk. The consistency between assessment results and actual operation of cities indicates this model can be applied and effective to some extent.

Openings including their size, shape and distribution in rock play a significant role in the performance of rock related structures. The well-established knowledge in this area can contribute to the engineering practices, for example, underground space design, planning and optimisation in Civil and Mining Engineering and wellbore stability in Drilling Engineering, among others. Thus, understanding the failure mechanism of rock with openings is theoretically and practically meaningful. Laboratory testing on rock or rock-like materials with openings have been studied extensively in the literature, which, however, primarily focuses on the cracks/fractures. In this paper, a comprehensive numerical study on the effect of non-banded openings, i.e., circular, rectangular, and triangular opening, on the rock mechanical behaviour is performed using a hybrid continuum-discrete element method. It is revealed that the proposed simulation method can reproduce reasonably the crack initiation and propagation, and predict well the change of the mechanical behaviour due to the openings. In addition, the influence of the opening shape and opening ratio (=area of opening/specimen area) on the mechanical behaviour is also investigated.

For rockbolts subjected to tensile loads, there exists a unique local slip–strain relationship as well as a unique bond–slip relationship between rockbolts and rock mass. An analytical model is presented in this study for fully grouted rockbolts under tension, based on the slip–strain relationship of rockbolts. This analytical model takes into account the trilinear bond–slip relationship and the pre- and post-yielding characteristics of the rockbolt material. The reliability and accuracy of the proposed analytical model are verified by experimental pullout tests. Verification studies show that the proposed model is capable of representing the strain and stress distributions of the rockbolts, and the overall load–displacement relationships of rockbolts before and after yielding. Additionally, the model has successfully captured the decoupling mechanism at the bolt–rock interface.