An Euler-Euler large eddy simulation (LES) of transient gas-liquid turbulence flow in a bubble column was conducted to investigate the adaptiveness of various sub-grid scale (SGS) models. The ...performance of three SGS models, respectively the standard Smagorinsky model, the wall-adapting local eddy (WALE) model and the Dynamic model, on the predictions of bubbly flow was studied. Comparison between SGS models for time-averaged and transient velocities, gas void fraction, power spectrum density (PSD), SGS turbulent dissipation, SGS turbulent kinetic energy, and Reynolds stress is conducted. The transient multi-scale irregular vortex structures, fluctuation characteristics of liquid motion and spiral floating motion of bubbles can be well captured by LES. The Dynamic model and WALE model with CW = 0.325 give reasonably better agreement with the time-averaged experimental data. The transient fluctuation behavior of gas-liquid turbulent flow can be correctly captured by the current Euler-Euler LES model, whatever the SGS model. The classical −5/3 law of PSD of vertical liquid velocity is hold properly in the low frequency region. The slope of PSD is around −25/3 at the high frequency region. The Smagorinsky model and WALE model are sensitive to the model constant, at least for the energy transfer of high frequency. The molecular dissipation is negligible compared to the SGS turbulent dissipation. The Dynamic model gives higher predictions for fluctuation amplitude and time-averaged values of both SGS turbulent dissipation rate profile and SGS turbulent kinetic energy profile than other SGS models. A certain calculation time is needed to reach the dynamic stable state in LES, and the specific time is related to the scale of the calculation model.
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•Adaptiveness of various SGS models in LES for two-phase turbulent flow is studied.•First to study SGS turbulent dissipation, SGS turbulent kinetic energy, and Reynolds stress tensor for bubbly flow.•A certain calculation time is needed to reach dynamic stability process in LES.
Conclusions regarding the association between antithyroid antibodies or thyroid dysfunction and rapid cycling bipolar disorder (RCBD) have been conflicting. Previous studies suggest that the impact ...of antithyroid antibodies on mental wellbeing seems to be independent of thyroid function. Here, we investigated their independent association with RCBD in a large, well-defined population of bipolar disorder (BD).
Fast serum levels of free thyroxine (FT4), free triiodothyronine (FT3), thyroid Stimulating Hormone (TSH), TPO-abs and Tg-abs were simultaneously measured in 352 patients with BD. Clinical features of BD were collected through semi-structural interview conducted by trained interviewers with background of psychiatric education.
Neither hypothyroidism nor hyperthyroidism was significantly associated with RCBD. Both TPO-abs and Tg-abs were significantly related to RCBD, even after controlling for gender, age, marriage status, education, antidepressants treatment, comorbidity of thyroid diseases, and thyroid function (serum levels of FT3, FT4 and TSH). Although TPO-abs and Tg-abs were highly correlated with each other, binary logistic regression with forward LR selected TPO-abs, instead of Tg-abs, to be associated with RCBD. TPO-abs was significantly, independently of Tg-abs, associated with hyperthyroidism, while Tg-abs was marginally significantly related to hypothyroidism at the presence of TPO-abs.
TPO-abs might be treated as a biomarker of RCBD. Further exploring the underlying mechanism might help understand the nature of RCBD and find out new treatment target for it.
Flapping wing micro aerial vehicles (FWMAVs) have attracted more attention during the development of the robotic systems field. The size of the flapping wing plays an important role in the lift force ...and torque generation based on quasi-steady aerodynamic model. Therefore, it is necessary to study energy-efficient design methods for wings to provide sufficient lift force and torque with minimal energy consumption for hovering flight. In this paper, the sensitive parameters for the lift force and power consumption were first selected based on design of experiment (DOE) and the parameter of the distributed wing stiffness was determined based on experimental data. Design optimization models for three different cases were then built by considering the lift force as one constraint and the energy consumption as the objective function. The combination of subset simulation and the gradient-based optimization was finally used for solving design optimization models, and the corresponding sensitivity analysis was provided.
•A high-performance Prussian blue analog was prepared by controlled nickel–cobalt doping.•Prussian blue's framework offers good sodium storage capacity and cycling stability.•Ni-Co ratio was ...controlled to prepare PB analogs.•A PB analog with Ni:Co=1:2 ratio showed high desalination capacity and rate.•The obtained PB analog retained 98% of its capacity after 50 cycles.
The unique framework structure of Prussian blue imparts excellent sodium storage capacity and cycling stability, thus making it an ideal capacitive deionization (CDI) electrode. Herein, Prussian blue analogs were prepared by the controlled doping of nickel–cobalt bimetallic ions to improve their desalination capacity and stability. Process parameters such as cell potential, current, inlet flow rate, and solution concentration were investigated to determine the optimal conditions for Prussian blue desalination, and a high-performance Prussian blue analog (CNF-4) was successfully synthesized by accurately controlling the nickel–cobalt doping ratio. The desalination capacity and rate of CNF-4 (Ni:Co=1:2) reached 65.31 mg g−1 and 4.38 mg g−1 min−1, respectively, and 98% of the capacity retention rate was maintained after 50 cycles of desalination. The excellent capacity and performance of the CNF-4 material indicate its superiority to conventional PBA CDI electrodes and its prospective applications in seawater desalination.
A ¼-scale water-model experiment is conducted to investigate the trajectories, velocities and size distribution of bubbles in a continuous-casting mold. A high-speed camera and a laser are used to ...record the transient bubble distribution. The region of interest is delimited to include the motion range of floating bubbles in the upper mold, and divided into 70 subregions of seven rows and 10 columns. Information on the trajectories, velocities and size distributions of bubbles is obtained from image sequences, using the ImageJ software. The effects of water/gas flow rates on the transport and size distribution of bubbles are studied. The results show that the motion range of larger bubbles decreases toward the submerged entry nozzle (SEN) and the floating direction of larger bubbles moves closer to vertical. The increase in water flow rate increases the level transportation distance of bubbles along the jet flow and the intensity of upper circulation flow, which has a complex effect on bubble transportation near the SEN. An increase in the gas flow rate contributes to the ascending flow near the SEN and significantly increases the bubble number in the region of interest for the entire bubble-diameter range, without causing an increase in mean bubble diameter.
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•Transient trajectories and velocities of various bubbles were firstly obtained from water model experiments.•Bubble size distribution at various water and gas flow rates were analyzed in detail.•Average diameter and number of bubbles at different regions were analyzed.
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•The influence of the different anions on the electrochemical performance of Co3X4 is studied and analyzed with DFT.•Co3O4 and Co3Se4 are synthesized with a simple novel two-step ...hydrothermal method, which will be applied for the synthesis of electrical materials with specific structure.•The redox reactions of Co3O4 during the charge–discharge process are obtained.•Co3Se4 shows better performance than Co3O4 due to the morphology and conductivity.
In order to investigate the influence of the anions on the electrochemical performance of cobalt-based compounds, Co3O4 and Co3Se4 are studied and theoretically analyzed with the density functional theory (DFT). Avoiding of the traditional synthesis of the high-temperature annealing for the transition metal oxides, the cubic spinel phase Co3O4 on a nickel foam (NF) substrate with a simple two-step hydrothermal method and Co3Se4 with the core-branched structure by anions exchange method are prepared. The electrochemical measurements show that the capacitance and conductivity of Co3Se4 are significantly better than those of Co3O4, and Co3Se4 still maintain high capacity at high current density. Furthermore, the kinetics of electrode material Co3O4 and Co3Se4 are analyzed and compared. According to the calculation of the density of states, the results show the band gap of Co3O4 is 2.18 eV and the Fermi energy line of Co3Se4 enters into the conduction band, which means the conductivity of Co3Se4 is better than that of Co3O4. Additionally, three redox reactions during the charge and discharge process of Co3O4 are determined and the band gaps changes are also calculated.
•The mixed columnar-equiaxed solidification during steel strip feeding in continuous casting was studied.•Steel strip feeding can improves solidification quality by increasing the equiaxed grain ...percentage.•A mathematical relationship between equiaxed grain percentage and initial temperature and size of strip was established.
Feeding a steel strip into a continuous casting (CC) mold is an effective method for improving the internal quality of CC slabs. An alloy experiment and three-phase mixed columnar-equiaxed solidification modeling were used to investigate the solidification structure evolution during the cold strip feeding process. The Euler method was adopted to treat the liquid phase, columnar grain phase, and equiaxed grain phase as continuous phases, and the mass, momentum, energy, and species transport equations of each phase, as well as the equiaxed grain density equation, were solved simultaneously. A comparison of the simulation and experimental results shows that the model can be used for calculating phase transitions, thermal-solute convection, grain deposition, macro-segregation, and the transformation of columnar grains into equiaxed grains in the solidification-melting system, which reveals the inherent relationship between the cold strip parameter and equiaxed grain percentage that is unquantifiable in the experiments. The results show that cold strip feeding improves the solidification structure quality by accelerating nucleation, strengthening convection, and promoting the columnar-equiaxed grain transition (CET). The subcooling nucleation rate around the cold strip first increases to a maximum and then decreases over time. A mathematical relationship between the equiaxed grain percentage and the initial temperature and size of the cold strip was established.
A population balance model based on the multiple-size-group (MUSIG) approach was developed to investigate the multi-size bubbly flow in a slab continuous casting mold. Firstly, effects of the bubble ...size group number, the initial bubble diameter, and the calibration factors for breakage and coalescence in MUSIG model on the multi-size bubbly flow were discussed in detail. Then, effects of both the water and gas flow rates on the bubble size distribution, the gas volume fraction, and the turbulence intensity of liquid phase were investigated. A relatively high water flow rate intensified the turbulence in the upper recirculation region of the mold and also eased the turbulence near the submerged entry nozzle (SEN) by promoting the breakage and horizontal transportation of bubbles; thus, an appropriate water flow rate is essential for better stability with a lower turbulence intensity near the SEN to prevent exposed slag eye formation and slag entrainment. With increase in the gas flow rate, the mean bubble diameter and gas volume fraction increased significantly, the turbulence near the SEN was also significantly increased, but this effect was much weaker in the region away from the SEN.
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•Bubble initial diameter and size group number in MUSIG model is optimized.•Effects of calibration factors for coalescence and breakage models are discussed.•Bubble redistribution behavior due to variation of operating parameter is revealed.
Multi-size bubbly flow in a one-quarter-scale water model of a continuous casting mold was simulated using the inhomogeneous multiple size group (IMUSIG) model. The Sauter mean bubble diameter, gas ...volume fraction, interfacial area density, turbulence kinetic energy, and velocity field predicted by the IMUSIG and multiple size group (MUSIG) models were compared. The IMUSIG model separated the motions of the small and large bubbles on the basis of two velocity groups, and both models adopted 15 size groups. The results showed that the IMUSIG model better reflected the bubble size distribution near the nozzle. Small bubbles were further transported by the jet flow, which enlarged the bubble cluster range and decreased the gas volume fraction and interfacial area density in the upper part of the submerged entry nozzle, likely diminishing the coalescence rate in this region; consequently, the overestimation of Sauter mean bubble diameter outside the nozzle was corrected. The liquid-phase flow fields predicted by the IMUSIG and MUSIG models were very similar, and the IMUSIG-predicted magnitudes of velocity and turbulence kinetic energy were only slightly lower than the MUSIG predictions; this slight difference is attributable to the expanded bubble cluster range and higher interfacial area density, which weakened the upper recirculation in the IMUSIG model.
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•The IMUSIG model is innovatively applied in continuous casting mold.•The overestimation of bubble size near nozzle is diminished by the IMUSIG method.•Separating the bubble motion by size is found meaningful for laterally injected bubbly flow.
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•This was the first application of oxygenated vacancy cobalt tetroxide/polypyrrole(Ov-Co3O4@PPy) composites in the field of supercapacitors;•Regulate the concentration of NaBH4 ...solution (essentially the amount of Co2+), realize the enhancement of the specific capacitance of the material and the diversification of the morphology, and the trend of the obtained concentration and specific capacitance can be widely used in the field of defective transition metal oxides;•A new idea for constructing a defective transition metal oxide/conductive polymer core–shell structure was proposed, in which the vacancy structure and the core–shell structure together impart high specific capacitance and high energy density to the material.
Effective controllable manufacturing oxygen vacancy and polypyrrole coating can optimize the capacitive and cyclic properties of Co3O4. Herein, composition of Ov-Co3O4@PPy with Co3O4 rich in oxygen vacancy defects and polypyrrole was synthesized using NaBH4 reduction and chronoamperometry. Ov-Co3O4 was synthesized while regulating the concentration of the reducing agent NaBH4 solution, and then Ov-Co3O4@PPy was synthesized by electrodeposition of PPy. The specific capacitance of Ov-Co3O4@PPy formed at an optimal NaBH4 concentration and electrodeposition time was about three times that of Co3O4 without reduction treatment and unwrapped PPy. The capacitance retention rate of Ov-Co3O4@PPy was close to 80.5% after 5000 cycles. In addition, Ov-Co3O4@PPy//AC asymmetric supercapacitor was assembled with the as-prepared Ov-Co3O4@PPy as the positive electrode material and activated carbon as the negative electrode, which yielded specific energy density up to 74.55 Wh kg−1 at 850 W kg−1 power density and a capacitance retention rate close to 110% after 10,000 cycles.
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