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Results of a series of 3D and 2D analyses of open-face tunnelling in marly-clayey deposits are presented in the paper. A parametric study was performed to investigate the influence of initial stress state, soil deformability, shea...
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Results of a series of 3D and 2D analyses of open-face tunnelling in marly-clayey deposits are presented in the paper. A parametric study was performed to investigate the influence of initial stress state, soil deformability, shear strength parameters, and soil anisotropy, on settlement prediction. Comparison of 2D and 3D results shows that the settlement trough predicted by 2D analysis agrees well with 3D results when an appropriate amount of unloading prior to lining installation is adopted. It is demonstrated that the load reduction factor significantly depends on shear strength parameters of soil.
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The development of intermetallic γ′,γ″ precipitates and γ′/γ″ co-precipitates in Inconel 706 during exposure at a service temperature of 750℃ is investigated. The distributions of elastic strain energy and mean normal str...
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The development of intermetallic γ′,γ″ precipitates and γ′/γ″ co-precipitates in Inconel 706 during exposure at a service temperature of 750℃ is investigated. The distributions of elastic strain energy and mean normal stresses around the interfaces of precipitates arise from the lattice-mismatch and are calculated by means of three-dimensional finite element (FE) analysis. The highest energy density is found at the γ′/γ and γ″/γ interfaces. The total strain energy per γ″ and γ? precipitates in matrix is three times larger as the total strain energy per γ′/γ″ co-precipitate. We find that a γ″-precipitate is energetically unstable and tends to merge with a γ′-precipitate creating a γ′/γ″ co-precipitate. The long-range stress field can considerably reduce the mean normal stresses around γ″/γ interfaces.
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This paper provides an efficient and rigorous model for 3D seismic analysis of long lined tunnels considering wave passage effects. By taking advantages of the 2.5D model, computation effort is considerably reduced. The water-satu...
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This paper provides an efficient and rigorous model for 3D seismic analysis of long lined tunnels considering wave passage effects. By taking advantages of the 2.5D model, computation effort is considerably reduced. The water-saturated poroelastic half-space is modelled as two-phase media and soil nonlinearity is considered via the equivalent linear approach. This improved model is realized by a finite element-indirect boundary element (FEIBE) coupling method. The study reveals that the wave passage effect causes significant longitudinal deformation of the tunnel, and differences in the tunnel seismic responses between the two-phase half-space case and the single-phase half-space case are not negligible.
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In this study, a nanocomposite of polypyrrole-coated magnetite nanoparticles (Fe3O4@PPy) was prepared by ultrasonic-microwave technique, and employed as magnetic solid-phase extraction (MSPE) sorbent for extraction of vitamin D fr...
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In this study, a nanocomposite of polypyrrole-coated magnetite nanoparticles (Fe3O4@PPy) was prepared by ultrasonic-microwave technique, and employed as magnetic solid-phase extraction (MSPE) sorbent for extraction of vitamin D from milk samples. The term of the synthesis by ultrasonic-microwave technique was dramatically shortened within 4 h compared to 20 h by conventional stirring-heating method. The resultant composites incorporating the pi-pi bonding (between PPy coating and the analytes) and magnetic separation can be applied for vitamin D analysis in complicated samples. Without saponification or protein precipitation, vitamin D-2 and vitamin D-3 could be captured directly from milk samples by Fe3O4@PPy, and separated by magnetic field with only 0.5 mL desorption solvent. The total preparation time was completed within 15 min. A method for the determination of vitamin D in milk samples by the Fe3O4@PPy extraction coupled with high performance liquid chromatography (HPLC) was developed. The LODs of vitamin D-2 and vitamin D-3, based on signal-to-noise ratio (S/N) of 3, were 0.02 ng/mL and 0.05 ng/mL respectively. The recoveries of vitamin D-2 and vitamin D-3 from milk samples were in the range of 71.9-90.3%, with relative standard deviations ranging between 3.6%-9.9%. The results indicated that the Fe3O4@PPy can be favorably used for the extraction of the vitamin Din milk samples. (C) 2016 Elsevier B.V. All rights reserved.
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Three-dimensional (3D) metallogenic prospectivity modeling has become increasingly important in deep Fe-Cu skam mineralization prospecting. The selection of prediction models and their comparison are of great significance. In this...
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Three-dimensional (3D) metallogenic prospectivity modeling has become increasingly important in deep Fe-Cu skam mineralization prospecting. The selection of prediction models and their comparison are of great significance. In this paper, we integrated the geological and geophysical data from the Zhuchong Fe-Cu deposit in the Yueshan orefield (Anhui, eastern China) to establish the local 3D geological framework. We extracted the 3D ore-controlling factors quantitatively by means of 3D spatial analysis methods, and compared the 3D mineralization locations predicted by the weight of evidence method and the artificial neural network method. The results show that both methods can locate most of the known orebodies, suggesting that both are relatively reliable. In addition, the weight of evidence method performed distinctly better than the artificial neural network method in terms of both prediction effectiveness and efficiency. Therefore, the weight of evidence method may be more applicable in 3D prospectivity modelling for Fe-Cu skarn deposits in the region. Finally, the composite area predicted by the two methods is taken as the final prediction result of the mineralization area of the deposit. And it is suggested that in the quantitative 3D prediction, multiple selection of different methods with good adaptability should be involved in the prediction at the same time, and compound prediction method should be used to delineate the target area. Our work has guiding significance for future deep prospecting and exploitation for other similar Fe-Cu skarn deposits.
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Tunnelling analysis is a matter of 3-D cases rather than 2-D. In fact, to examine stress redistribution and ground response to tunnelling ahead and behind the tunnel face, 3-D FE analysis is required to be conducted. The objective...
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Tunnelling analysis is a matter of 3-D cases rather than 2-D. In fact, to examine stress redistribution and ground response to tunnelling ahead and behind the tunnel face, 3-D FE analysis is required to be conducted. The objective of this paper is to describe and evaluate 2-D and 3-D Finite Element (FE) analyses for New Austrian Tunnelling Method (NATM) in soft ground. First, 2-D plane strain FE analyses were conducted. The best 2-D model whose predictions were in a great agreement with the field measurements was found to be sequential excavation model (SEN), which follows closely the construction sequences used in the field. Second, 3-D FE analysis has been carried out to predict transverse and longitudinal surface settlement profiles over the tunnel centreline using the SEM process as this model produced the best predictions in 2-D analysis. In order to take account the deformations prior to lining installation Hypothetical Modulus of Elasticity (HME) soft lining approach were adopted. In this method, predetermined HME values for the lining are introduced to consider the ground deformation prior to shotcrete installation and until the shotcrete gains their full strength, green shotcrete behaviour. Karakus (2003) reported that the amount of reduction factor (δ) for the lining elasticity modulus ranges from 0.02 to 0.1 for the overconsolidated London clay. Measurements recorded during construction of the Heathrow Express Trial tunnel, Type-2 single sidewall excavation, were used to compare the performances of both 2-D and 3-D FE analyses.
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This paper presents a fast design method taking into account 3-D effects in a reinforced brushed dc motor used as starter in automotive application. Because of their low cost and simplicity, reinforced starters are used in micro-h...
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This paper presents a fast design method taking into account 3-D effects in a reinforced brushed dc motor used as starter in automotive application. Because of their low cost and simplicity, reinforced starters are used in micro-hybrid vehicles. The specific geometry of such devices induces an axial component of the flux which cannot be accounted for by 2-D models. 3-D finite element (FE) models are suitable for this purpose but their excessive need of CPU time complicates their use in an automatic optimization procedure. We propose to identify the overhang effects by using an adapted and corrected 2.5-D FE model which is validated by 3-D computations and experiments. Finally, the 2.5-D model is implemented in a multiobjective optimization procedure.
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Two-dimensional (2D) magnetic materials have attracted extensive research attention in recent years due to their promising potential for use in nanoscale spintronic devices. Although most of them are synthesized by the mechanical ...
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Two-dimensional (2D) magnetic materials have attracted extensive research attention in recent years due to their promising potential for use in nanoscale spintronic devices. Although most of them are synthesized by the mechanical exfoliation method from their layered bulk counterparts, due to their weak interlayer interactions, recently synthesized 2D non-van der Waals (non-vdW) ultrathin magnetic materials have revealed a novel direction for the discovery of 2D materials and the exploration of the corresponding applications. This review provides an overview of the recent progress in the non-vdW magnet family from the perspectives of both experimental and theoretical research. We first briefly introduce the synthesis methods and intrinsic properties of these non-vdW magnetic materials, and then summarize the electronic and magnetic properties available via doping/substitution, surface passivation, and heterostructure constructions. Promising research routes and challenges are also discussed at the end of the review. It is expected that this overview of 2D non-vdW magnets will provide guidelines for researchers in this field and inspire further exploration of new spintronic devices.
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Recently, multifunctional and highly porous transition metal oxide-based anode materials have attracted increasing attention in enabling the high capacity and stability for lithium-ion battery (LIB) applications. Herein, an ingeni...
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Recently, multifunctional and highly porous transition metal oxide-based anode materials have attracted increasing attention in enabling the high capacity and stability for lithium-ion battery (LIB) applications. Herein, an ingenious and facile approach has been developed to prepare three-dimensional (3D) porous and spindle-like alpha-Fe2O3 nanostructures with controlled morphologies and they are used as an effective anode in LIBs. The morphology of the spindle-like alpha-Fe2O3 nanostructures was systematically tuned concerning the growth temperatures of 160,180 and 200 degrees C and they are denoted as FO-160, FO-180 and FO-200, respectively. Owing to the high surface area and porosity, 3D porous FO-180-based LIB exhibited a better cycle performance and good rate capability compared to the FO-160 and FO-20 0 electrodes. To be specific, the FO-180 electrode delivered a maximum discharge capacity of 965 mAh g(-1) at a current density of 500 mA g(-1) over 150 cycles, which is comparatively higher than the FO-160 (598 mAh g(-1)) for and FO-200 and (405 mAh g(-1)) electrodes, respectively. The outstanding electrochemical characteristics in terms of reversibility and rate performance of spindle-like alpha-Fe2O3 nanostructures are attributed to the 3D porous structure with a large surface area of the sample. (C) 2020 Elsevier B.V. All rights reserved.
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Two two-dimensional/one-dimensional (2-D/1-D) methods, fusion and hybrid, have been developed and reported in the literature to deal with three-dimensional (3-D) heterogeneous reactor problems and to avoid direct 3-D transport cal...
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Two two-dimensional/one-dimensional (2-D/1-D) methods, fusion and hybrid, have been developed and reported in the literature to deal with three-dimensional (3-D) heterogeneous reactor problems and to avoid direct 3-D transport calculations. The 2-D/1-D fusion method transforms a 3-D transport problem into 2-D and 1-D transport problems that have a smaller computational burden than the original problem. The hybrid method uses an additional diffusion (or SP_3) approximation in the axial direction to enhance the efficiency of the calculation. This paper presents and compares the stability and the accuracy of the two methods. To this end, a 2-D transport problem is considered by reducing one dimension in the radial direction, leading to 1-D/1-D fusion or hybrid method. Fourier stability analysis is used to study the stability and the convergence behaviors of the two methods. With respect to accuracy, the two methods are compared via numerical solutions on a typical 2-D reactor problem. The results indicate that the fusion method is stable and gives a very accurate transport solution. On the other hand, the hybrid method requires a stabilizing scheme, and the diffusion approximation in the axial calculation causes significant errors.
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