| 1. |
- Li, Wang, et al.
(author)
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Annealing parameters effect on microstructure evolution, tensile properties and deformation behaviors of direct-cold-rolled UNS S32101 duplex stainless steel with heterogeneous layered structure
- 2023
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 883
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Journal article (peer-reviewed)abstract
- Microstructure evolution, strain-induced martensite transformation (SIMT) kinetics, tensile properties, deformation behaviors of UNS S32101 duplex stainless steel (DSS) with heterogeneous layered structure (HLS) were investigated. HLS composed of multiscale grains (spanning coarse, fine, and ultrafine grains) was prepared by direct cold rolling in combination with short-time annealing, being dominated by coarse-grained ferrite (CGed α) and fine-grained austenite (FGed γ). A quantitative SIMT kinetics model was established to predict the α′-martensite fraction at various strain/annealing parameters, indicating that increased average grain size (AGS) for γ not only contributed to the SIM formation but also promoted the monotonic increase of SIMT rate until annealing for 10 min. Relatively high stacking fault energy (SFE, 35.89∼39.34 mJ/m2) favored mechanical twinning as the dominant deformation mode of γ accompanied by SIMT and dislocation glide. And α deformation was mainly coordinated by wavy slip. Both SFE and Olson-Cohen parameters were strongly correlated with the γ AGS, which could reasonably interpret the dependence of SIMT on the AGS. The A and B values increased progressively with grain coarsening along with the rapid decline in SFE, facilitating the martensite formation. Further increasing the AGS beyond the peak region severely suppressed SIMT probably due to the low probability of martensite embryo generation at deformation twins (DTs) intersections, coinciding with the sharp decrease A value.
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| 2. |
- Li, Wang, et al.
(author)
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Correlation of microstructure and dynamic softening mechanism of UNS S32101 duplex stainless steel during elevated temperature tensile testing
- 2022
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 855
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Journal article (peer-reviewed)abstract
- The dynamic substructural development and softening mechanism of UNS S32101 duplex stainless steel were comprehensively investigated by employing hot-tensile tests at various strain rates of 0.1-10 s(-1) at a fixed temperature of 1200 degrees C. Different flow behaviors were attributed to the microstructural evolution and restoration process under various hot-deformation conditions. The alternative restoration mechanisms of ferrite in the current alloy were closely associated with the evolution of the misorientation angle in the (sub)grains, depending on the applied strain rates. Therein, three distinct softening mechanisms were found in ferrite, i) subgrain coalescence (SC) at 0.1 s(-1), ii) continuous dynamic recrystallization (CDRX) at 1 s(-1) and iii) subgrain rotationassisted discontinuous dynamic recrystallization (SR-assisted DDRX) at 10 s(-1). During SR-assisted DDRX process, new DRX nuclei were preferentially formed at the high-angle grain boundaries/phase boundaries (HAGBs/PBs) through the growth of highly misoriented subgrains. In contrast to ferrite, the available dynamic softening behavior of austenite, unlike the classical DDRX mechanism characterized by strain-induced boundary migration (SIBM), is affected by a limited number of pre-existing HAGBs. At lower strain rates of 0.1 and 1 s(-1), the nucleation process of DRX in austenite is analogous to the CDRX behavior, whereas the growth characteristics conform to DDRX, thus, it can be called dynamic recovery-assisted DDRX (DRV-assisted DDRX). At a high strain rate of 10 s(-1), DRX nucleation mainly took place through the strain-induced twin boundaries (TBs) transformation into HAGBs, and then rapidly grew via SIBM, referred to as TB-assisted DDRX.
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| 3. |
- Li, Wang, et al.
(author)
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New comprehension on the microstructure, texture and deformation behaviors of UNS S32101 duplex stainless steel fabricated by direct cold rolling process
- 2022
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 845, s. 143150-
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Journal article (peer-reviewed)abstract
- The effect of cold deformation on the detailed microstructure evolution, texture development and deformation behaviors/mechanisms of UNS S32101 duplex stainless steel (DSS2101) during the direct cold rolling process was investigated. The results showed that throughout the cold deformation process, the negative texture of {001}<110> component was nonexistent in deformed ferrite, and most texture components were mainly concentrated on alpha/gamma-fibers. Detwinning in austenite was substantial responsible for the reorientation in {111}< 112> towards {111}<110> of gamma-fiber in ferrite rather than martensite transformation. Austenite texture were composed of {110}<100> Goss and {110}<115> Goss/Brass components at heavy deformation (50% and 70%). The refinement and deformation behavior in ferrite was attributed to microbands (MBs) subdivision and dislocation activities, whilst that of austenite mainly occurred through twinning, strain induced detwinning (SID) and strain induced martensite (SIM).
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| 4. |
- Li, Wang, et al.
(author)
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Partitioning behavior of N and its effect on hot deformation behavior of duplex stainless steels 2101 and 2205
- 2022
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In: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 57:48, s. 22119-22139
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Journal article (peer-reviewed)abstract
- In this paper, the N back-migration and restoration behavior of duplex stainless steels (DSSs) 2101 and 2205 (DSS2205) were studied. Experimental findings indicated that the Cr2N in the ferrite (α) persistently decreased for both steels during the cooling process from 1200 °C to 1000 °C, and the disappearance rate of Cr2N in DSS2205 was significantly faster than that of lean duplex stainless steel 2101 (LDX2101). On the one hand, due to the severe partitioning behavior of N atoms in α migrating back to austenite (γ), on the other hand, the enriched Mn in LDX2101 and the enriched Ni in DSS2205 exerted an impact on N migration. Also, the cumulative thermal deformation at 1200 °C contributed to the N migration back into γ with the assistance of high-density dislocations and thermal deformation energy. Furthermore, the softening mechanism of constituent phases was dominated by discontinuous dynamic recrystallization (DDRX) mechanism in both steels at a strain rate of 10 s−1, which was characterized by strain-induced boundaries migration from low-density dislocations to high ones.
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| 5. |
- Luu, Tien Duc, et al.
(author)
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Single particle conversion of woody biomass using fully-resolved and Euler–Lagrange coarse-graining approaches
- 2024
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In: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 368
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Journal article (peer-reviewed)abstract
- The conversion of woody biomass is studied by means of a layer-based model for thermally-thick biomass particles (Thunman et al. 2002, Ström et al. 2013). The model implementation is successfully validated against experiments that study particle conversion in a drop tube reactor. After this validation step, this work focuses on the well-known problem of grid dependence of two-phase numerical simulations using the standard Euler–Lagrange (EL) framework. This issue is addressed and quantified by comparing EL data that models the particle boundary layers to corresponding simulations which fully resolve these boundary layers (fully-resolved, FR, simulations). A comparison methodology for the conceptually different FR and EL approaches by extracting the heat transfer coefficient from the detailed FR simulations is proposed and confirms that the EL results are strongly grid-dependent. This issue is overcome by applying a set of coarse-graining methods for the EL framework. Two coarse-graining methods are evaluated, a previously suggested diffusion-based method (DBM) and a new approach based on moving averages referred to as MAM. It is shown that both DBM and MAM can successfully recover the detailed FR data for pure particle heating for a case where the grid size is half the particle diameter, i.e. when the standard EL method fails. Both coarse-graining methods also give improved results for an EL simulation that considers the more complex combined physics of particle heating, drying and devolatilisation, given that the CG model parameters that scale the corresponding CG interaction volumes are sufficiently large. Based on the available FR data, recommended model parameter ranges for DBM and MAM are provided as a function of normalised boundary layer thickness. The novel MAM approach is shown to be significantly more efficient than the DBM and therefore suitable for future EL simulations with multiple particles.
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| 6. |
- Yan, Jinci, et al.
(author)
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Identification of FtfL as a novel target of berberine in intestinal bacteria
- 2023
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In: BMC Biology. - 1741-7007. ; 21:1
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Journal article (peer-reviewed)abstract
- Background: Berberine (BBR) is a commonly used anti-intestinal inflammation drug, and its anti-cancer activity has been found recently. BBR can intervene and control malignant colorectal cancer (CRC) through intestinal microbes, but the direct molecular target and related mechanism are unclear. This study aimed to identify the target of BBR and dissectrelated mechanisms against the occurrence and development of CRC from the perspective of intestinal microorganisms. Results: Here, we found that BBR inhibits the growth of several CRC-driving bacteria, especially Peptostreptococcus anaerobius. By using a biotin-conjugated BBR derivative, we identified the protein FtfL (formate tetrahydrofolate ligase), a key enzyme in C1 metabolism, is the molecular target of BBR in P. anaerobius. BBR exhibits strong binding affinity and potent inhibition on FtfL. Based on this, we determined the crystal structure of PaFtfL(P.anaerobius FtfL)-BBR complex and found that BBR can not only interfere with the conformational flexibility of PaFtfL tetramer by wedging the tetramer interface but also compete with its substrate ATP for binding within the active center. In addition, the enzymatic activities of FtfL homologous proteins in human tumor cells can also be inhibited by BBR. Conclusions: In summary, our study has identified FtfL as a direct target of BBR and uncovered molecular mechanisms involved in the anti-CRC of BBR. BBR interferes with intestinal pathogenic bacteria by targeting FtfLs, suggesting a new means for controlling the occurrence and development of CRC.
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| 7. |
- Yang, Miao, et al.
(author)
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CFD modeling of biomass combustion and gasification in fluidized bed reactors using a distribution kernel method
- 2022
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In: Combustion and Flame. - : Elsevier Inc.. - 0010-2180 .- 1556-2921. ; 236
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Journal article (peer-reviewed)abstract
- A three-dimensional reactive multi-phase particle-in-cell (MP-PIC) model is employed to investigate biomass combustion and gasification in fluidized bed furnaces. The MP-PIC model considered here is based on a coarse grain method (CGM) which clusters fuel and sand particles into parcels. CGM is computationally efficient, however, it can cause numerical instability if the clustered parcels are passing through small computational cells, resulting in over-loading of solid particles in the cells. To overcome this problem, in this study, a distribution kernel method (DKM) is proposed and implemented in an open-source CFD code, OpenFOAM. In DKM, a redistribution procedure is employed to spread the solid volume and source terms of the particles in the parcel to the domain in which the particles are clustered. The numerical stiffness problem caused by the CGM clustering can be remedied by this method. Validation of the model was performed using data from different lab-scale reactors. The model was shown to be able to capture the transient heat transfer process in a lab-scale bubbling fluidized bed reactor under varying fluidization velocities and loads of sand. Then, the model was used to study the combustion/gasification process in a bubbling fluidized bed reactor under varying ambient temperatures, equivalent air ratios, and steam-to-biomass ratios. The performance of DKM was shown to improve the accuracy and the robustness of the model. © 2021 The Author(s)
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| 8. |
- Zhang, Jingyuan, 1992, et al.
(author)
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A novel coupling method for unresolved CFD-DEM modeling
- 2023
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In: International Journal of Heat and Mass Transfer. - : Elsevier Ltd. - 0017-9310 .- 1879-2189. ; 203
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Journal article (peer-reviewed)abstract
- In CFD-DEM (computational fluid dynamics-discrete element method) simulations particles are considered Lagrangian point particles. The details of the flow near the particle surface are therefore not fully resolved. When the particle scale is larger than the resolved flow scale, the coupling between the CFD model and the DEM model is critical. An effective coupling scheme should minimize the risk of artificial influences on the results from choices of numerical parameters in implementations and consider efficiency and robustness. In this work, a novel coupling method is developed. The method includes both the smoothing of the particle data and the sampling of the gas phase quantities. The smoothing employs the diffusion-based method. The gas sampling method can reconstruct the filtered fluid quantities at the particle center. The sampling method is developed based on the diffusion-based method with higher efficiency. The new method avoids mesh searching and it can be easily implemented in parallel computing. The developed method is validated by the simulation of a forced convection experiment for a fixed bed with steel spheres. With the well-posed grid-independent coupling scheme, the simulation results are in good agreement with the experimental measurements. The coupling effects and the computational cost are discussed in detail.
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| 9. |
- Zhang, Jingyuan, et al.
(author)
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Computationally efficient coarse-graining XDEM/CFD modeling of fixed-bed combustion of biomass
- 2022
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In: Combustion and Flame. - : Elsevier Inc.. - 0010-2180 .- 1556-2921. ; 238
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Journal article (peer-reviewed)abstract
- In the multi-scale modeling of a dense particle system, the particle phase and the gas phase can be modeled on vastly different scales. The coupling between the two models has a critical influence on the predictions obtained from the combined framework but can be accomplished in a variety of ways under different assumptions. In this work, a transient 3D model using a new coupling approach for fixed-bed combustion of biomass is presented. The developed model is formulated as an Eulerian-Lagrangian framework. A particle grid, generated based on the fluid grid, is applied as a transfer grid, and a diffusion operation is implemented to smooth the interactions between the gas phase and the particles. The interactions between gas and solid phases as well as the radiative heat transfer between particles are considered. The particle motion is resolved by the soft-sphere model, whereas the conversion is calculated based on a thermally thick particle model. All sub-models are optimized to enhance computational efficiency. The 3D model is validated by comparing the simulations with laboratory-scale experiments for a fixed-bed operated in counter-current combustion mode. The key simulation parameters are configured by sensitivity analysis. The simulation results are in good agreement with the experimental measurements, and the combustion regimes with different air inlet conditions are well captured. The coupling effects are discussed in detail. The particle grid size influences the prediction of the transient results, and the interplay between the heat transfer mechanisms inside the fixed-bed and the coupling scheme is thoroughly analyzed. Both inter-particle radiation and gas-to-particle convection play essential roles in the heat transfer inside the fuel bed, while the inter-particle heat conduction can be neglected. © 2021 The Authors
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| 10. |
- Zhang, Jingyuan, 1992, et al.
(author)
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Grid-independent Eulerian-Lagrangian approaches for simulations of solid fuel particle combustion
- 2020
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 387
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Journal article (peer-reviewed)abstract
- In this study, a computational fluid dynamics (CFD) model with three coarse graining algorithms is developed with the implementation of a layer based thermally thick particle model. Three additional coupling methods, cube averaging method (CAM), two-grid method (TGM) and diffusion-based method (DBM), are implemented. These coupling methods are validated and compared with the widely used particle centroid method (PCM) for combustion of a biomass particle in a single particle combustor. It is shown that the PCM has a strong dependence on the grid size, whereas the CAM and TGM are not only grid independent but also improve the predictability of the simulations. Meanwhile, a new parameter, the coupling length, is introduced. This parameter affects the sampling of the gas phase properties required for the particle model and the distribution of the solid phase properties. A method to estimate the coupling length by using empirical correlations is given. In general, it is found that a too small coupling length underestimates the heating-up rate and devolatilization rate, while a too large coupling length overestimates the O2 concentration at the particle surface. The coupling length also has an influence on the distribution of the gas phase products.
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