Mixing Configuration Research Articles

Nonlinear dispersion of backward-wave four-wave mixing in a photorefractive semiconductor and its effect on group velocity

Photorefractive backward-wave four-wave mixing may be configured for the amplification of the phase conjugate output and the attenuation of the transmitted output. The nondegenerate-in-frequency interaction is studied in such a configuration, realized in a semiconductor CdTe crystal. The spectra measured at different outputs show the gain and attenuation resonances. The preliminary study of optical pulse propagation demonstrates that, due to different nonlinear dispersions at different outputs of the selected wave mixing configuration, a slowing down of light is observed at the phase conjugate output, while an acceleration of light is detected at the transmitted output for the same input pulse at the same interaction.

Tandem Pt/TiO2 and Fe3C catalysts for direct transformation of CO2 to light hydrocarbons under high space velocity

CO2 hydrogenation to hydrocarbons under high space velocity is crucial for industrial applications, but traditional Fe-based catalysts often suffer from the low activity and poor stability. Herein, we report a new tandem catalyst system combining Pt/TiO2 catalysts with Fe3C catalysts for the direct conversion of CO2 into C2-C4 hydrocarbons under high space velocity. The Pt/TiO2 component promotes *CO intermediate production with an enhanced Reverse Water-Gas Shift (RWGS) reaction efficiency, providing a highly reactive species for the Fe3C catalyst to achieve Fischer-Tropsch synthesis (FTS). By maximizing the contact interface between the Pt/TiO2 and Fe-based components through a granule mixing configuration, we achieve significant enhancements in both CO2 conversion rate (24.0 %) and C2-C4 hydrocarbons selectivity (51.1 %) under the gaseous hourly space velocity (GHSV) of 100000 mL gcat−1h−1. Besides, excellent stability is achieved by the tandem catalysts with continuous catalysis for up to 80 h without significant decrease in activity. Through modulation of the reduction states of iron oxide, we effectively tune the composition of Fe-based catalyst, thereby tailoring the product distribution. Through this work, we not only offer a promising avenue for reducing CO2 for efficient CO2 utilization but also highlight the importance of catalyst design in advancing sustainable chemical synthesis.

Synergistic interplay of photobioreactor mixing and static mixer configuration on Rhodoseupdomonas palustris’s growth and biohydrogen production

Inducing light/dark (L/D) cycles through mixing or recirculating the media in a photobioreactor improves light utilization for biohydrogen production during photoferentation. However, the mutual shading effect is a key challenge for photofermentation using purple non-sulphur bacteria (PNSB). In this study, mixing was explored as a mitigating methodology through the investigation of three different static mixer configurations: concentric, spiral, and half-moon, across four laminar flowrates: 1.2 L/min, 0.71 L/min, 0.31 L/min and 0.15 L/min. At 0.15 L/min, the half-moon and spiral static mixers significantly improved specific and cumulative hydrogen production by 11.2-fold and 114 %, respectively. Also, recirculating the fluid via a peristaltic pump resulted in a significant shearing effect, impacting cell viability. Inducing L/D cycles via a static mixer was thus beneficial for hydrogen production over an increased flow rate. Additionally, biomass productivity increased by up to 70 %, reaching a cell dry weight of 7.0 g/L with the spiral static mixer configuration at 0.15 L/min flow rate. Interestingly, this study found that the static mixers only significantly increased specific hydrogen production and light conversion efficiency at the lowest flow rate of 0.15 L/min, beyond which they showed no significant improvement in biohydrogen production. This indicates that high L/D cycling frequencies are unnecessary to alleviate the mutual shading effect for R. palustris, which is advantageous for upscaling. These findings emphasise the potential of static mixers as an alternative to increase light conversion efficiency and industrial hydrogen production.

The modeling and simulation of a smoke-free firewood furnace designed for indirect heating adapted to mixing heating configuration

The use of wood furnaces for thermal energy applications in drying is common among coffee growers in Brazil. However, incomplete combustion of firewood and excessive use of damaged furnaces can lead to product contamination and negative environmental effects. To address this issue, a smoke-free wood furnace was designed, to heat the drying air utilizing a heat exchanger, and using a removable smoke-free combustion cell. The new furnace design was based on thermal energy ranging from 15 to 30 kW, drying airflow rates from 35 to 45 m³ min-1, and drying air temperatures from 50 to 80 °C. The design process considered the thermal energy required for heating air, furnace fuel consumption, combustion chamber volume, grate area, and heat exchanger dimensions. The performance of the adapted furnace data was monitored over time using a graphics statistical control (x-bar chart). Regression analysis of temperature and mass flow rate for the mixed heating configurations was carried out to develop quadratic models for the modified operation. The models were used to create a simulation model using ExtendTM simulation language to predict the performance of the furnace, in mixed heating at the desired drying air temperature. The simulation was carried out under two different conditions, normal and controlled operation of the furnace. Five scenarios of working hours without refueling (119 min) drying temperature were carried out. The simulation result indicates that the furnace operates at a maximum efficiency of approximately 40% irrespective of the desired drying temperature during normal operation. However, controlled operation with increased opening time of the mixing air inlet for admitting ambient air into the mixing chamber significantly improved the furnace's efficiency, with an optimum efficiency of 55% achieved at 90°C drying temperature. The simulation reflects that the furnace operates at a maximum efficiency of 68% at a temperature of 90°C, which can be attained at 66.31 minutes of operation in mixed heating of 30 minutes and indirect heating configuration of 89 min during working hours without refueling of 119 min.

Realization of Fine-Tuning the Lattice Thermal Conductivity and Anharmonicity in Layered Semiconductors via Entropy Engineering.

Entropy engineering is widely proven to be effective in achieving ultra-low thermal conductivity for well-performed thermoelectric and heat management applications. However, no strong correlation between entropy and lattice thermal conductivity is found until now, and the fine-tuning of thermal conductivity continuously via entropy-engineering in a wide entropy range is still lacking. Here, a series of high-entropy layered semiconductors, Ni1- x(Fe0.25Co0.25Mn0.25Zn0.25)xPS3, where 0 ≤ x < 1, with low mass/size disorder is designed. High-purity samples with mixing configuration entropy of metal atomic site in a wide range of 0-1.61R are achieved. Umklapp phonon-phonon scattering is found to be the dominating phonon scattering mechanism, as revealed by the linear T-1 dependence of thermal conductivity. Meanwhile, fine tuning of the lattice thermal conductivity via continuous entropy engineering at metal atomic sites is achieved, in an almost linear dependence in middle-/high- entropy range. Moreover, the slope of the κ- T-1 curve reduces with the increase in entropy, and a linear response of the reduced Grüneisen parameter is revealed. This work provides an entropy engineering strategy by choosing multiple metal elements with low mass/size disorder to achieve the fine tuning of the lattice thermal conductivity and the anharmonic effect.

Comparison of the performance of different mixing ventilation configurations in particle removal from indoor spaces

Re-suspended particles from indoor sufaces present a real threat to occupants. The ventilation system plays a primordial role in enhancing the indoor air quality. A CFD model was developed to compare particle removal effectiveness of variable mixed air distribution configurations. A parametric study was performed to assess the effect of two main factors affecting the airflow pattern: the relative inlet/outlet location and suction velocity. It was found that the mixing ventilation configuration with floor outlets located at middle of the walls presented the best performance due to the creation of a suction effect covering the majority of the floor area leading to high removal effectiveness. Furthermore, increasing the suction velocity strengthened the suction effect resulting in better particle removal by the escape of a larger number of particles generated at floor level.

High-efficiency detection of primary amine-based chiral molecules by a facile aldimine condensation reaction.

Detection of chiral molecules in a high-efficiency way is very important to meet the demands for chiral analysis in drug testing, asymmetric synthesis, etc. Herein, we have developed a novel route to realize the rapid determination of concentration and configuration of primary amine-based chiral molecules. An aldehyde functionalized acid & base-sensitive fluorane dye (R-C) was used as the active agent to be reacted with the chiral molecules through an aldimine condensation reaction. After the mixing operation, concentration and configuration of the detected chiral molecule could be facilely read from the UV-vis absorption spectra and CD spectra, respectively.

Analyzing Local Shear Rate Distribution in a Dual Coaxial Mixing Bioreactor Handling Herschel–Bulkley Biopolymer Solutions through Computational Fluid Dynamics

For the aeration of highly viscous non-Newtonian fluids, prior studies have demonstrated the improved efficacy of dual coaxial mixing bioreactors fitted with two central impellers and a close clearance anchor. Evaluating the effectiveness of these bioreactors involves considering various mixing characteristics, with a specific emphasis on shear rate distribution. The study of shear rate distribution is critical due to its significant impact on the mixing performance, gas dispersion, and homogeneity in aerated mixing systems comprising shear-thinning fluids. Although yield-pseudoplastic fluids are commonly employed in various industries, there is a research gap when it comes to evaluating shear rate distribution in aerated mixing bioreactors that utilize this fluid type. This study aims to investigate shear rate distribution in an aerated double coaxial bioreactor that handles a 1 wt% xanthan gum solution, known as a Herschel–Bulkley fluid. To achieve this goal, we employed an experimentally validated computational fluid dynamics (CFD) model to assess the effect of different mixing configurations, including down-pumping and co-rotating (Down-Co), up-pumping and co-rotating (Up-Co), down-pumping and counter-rotating (Down-Counter), and up-pumping and counter-rotating (Up-Counter) modes, on the shear rate distribution within the coaxial mixing bioreactor. Our findings revealed that the Up-Co system led to a more uniform local shear distribution and improved mixing performance.

Exploiting the prediction of mass transfer performance in aerated coaxial mixers containing biopolymer solutions using empirical correlations and neural networks

AbstractThe volumetric mass transfer coefficient is commonly used to assess the mixing effectiveness of gas–liquid bioreactor systems. Analyzing mass transfer performance in non‐Newtonian fluids inside coaxial mixers can be challenging due to the complex interaction between process variables, which requires developing robust characterization and estimation approaches. This study aims to investigate the gas dispersion in shear‐thinning biopolymers with yield stress using coaxial mixers in order to evaluate the effects of aeration and agitation on the volumetric mass transfer coefficient. A mixing configuration comprising a pitched blade turbine and an anchor was employed to disperse air into xanthan gum solutions, and the mass transfer performance was obtained at different impeller speeds and biopolymer concentrations by measuring the dissolved oxygen concentration. A dimensionless empirical correlation was proposed, and the results showed that the mass transfer was positively influenced by aeration intensity and agitation mechanism, quantified by the gas flow number and Reynolds number, respectively. Additionally, a strategy using stacking‐ensemble artificial neural networks was developed to accurately estimate the volumetric mass transfer coefficient, with a correlation coefficient of 0.998. The proposed mass transfer characterization approach overcame the complexities of analyzing aerated coaxial mixer systems and provided a reliable design model for bioreactor systems containing non‐Newtonian fluids.

Machine learning instructed microfluidic synthesis of curcumin-loaded liposomes

The association of machine learning (ML) tools with the synthesis of nanoparticles has the potential to streamline the development of more efficient and effective nanomedicines. The continuous-flow synthesis of nanoparticles via microfluidics represents an ideal playground for ML tools, where multiple engineering parameters – flow rates and mixing configurations, type and concentrations of the reagents – contribute in a non-trivial fashion to determine the resultant morphological and pharmacological attributes of nanomedicines. Here we present the application of ML models towards the microfluidic-based synthesis of liposomes loaded with a model hydrophobic therapeutic agent, curcumin. After generating over 200 different liposome configurations by systematically modulating flow rates, lipid concentrations, organic:water mixing volume ratios, support-vector machine models and feed-forward artificial neural networks were trained to predict, respectively, the liposome dispersity/stability and size. This work presents an initial step towards the application and cultivation of ML models to instruct the microfluidic formulation of nanoparticles.

Effect of hollow fiber configuration and replacement on the gas exchange performance of artificial membrane lungs

Artificial membrane lungs are composed of hollow fiber membranes. Blood flows with low velocities in the membrane bundle, forming a laminar boundary layer near the membrane surfaces that limits gas transfer. Passive blood mixing within the fiber array is utilized to overcome this limitation. Nevertheless, it is unclear to which extent blood mixing and fiber configuration contribute to the performance of membrane oxygenators.This study aims to evaluate the effect of fiber configuration and replacement on the gas exchange performance of membrane oxygenators to contribute to a better understanding of the influence of blood mixing to gas transfer and the mechanisms of gas exchange in blood. Furthermore, designs in which hollow fibers of different functions could be combined in highly integrated membrane lungs are provided.We analyzed the gas transfer performance of membrane oxygenators in a perpendicular configuration with 100%, 75%, or 50% of fibers open, and in a crossed configuration with 100% or 67% of fibers open. 95%–100% of the oxygen transfer of a fully open oxygenator could be maintained in our prototypes with 25% of gas exchange fibers closed in a perpendicular configuration, indicating that several fibers contributed to gas exchange by mixing the blood flow. Closing fibers in a perpendicular configuration resulted in a lower decrease in oxygen transfer. This study contributes to the development of novel membrane oxygenators integrating fibers of different functionalities (e.g. oxygenation and dialysis) maintaining high gas exchange efficiency.

Twin-screw continuous mixing: Effect of mixing elements and processing parameters on properties of aerosol powders

Twin-screw continuous mixing was used to prepare aerosol powders containing 1% budesonide, 0.3% magnesium stearate, and 98.7% α-lactose monohydrate. The effect of mixing configuration was studied using three screw profiles containing either a combing element, 30° forward kneading element, or a 60° forward kneading element. The impact of screw speed, feed rate, and multiple passes through the mixer on powder quality was investigated. The impact of specific energy on aerosol performance was dependent on the mixing configuration, and high energy input was detrimental to FPF for the 30° kneading element. Control of content uniformity was demonstrated by varying the mixing element in the screw profile. Passing the material through the mixer multiple times improved the aerosol performance. The robust and tunable nature of twin-screw mixing makes it a process well suited for continuous manufacturing of aerosol powders.

Description of 2_3^+, 0_3^+Intruder States in 130Xe Nucleus by Mixing of Transitional Hamiltonian and O(6) Casimir Operator

In this paper, we tried to describe the , intruder stats in 130Xe nucleus in a configuration mixing framework. To this aim, we have used a transitional Hamiltonian based in the affine SU(1,1) lie algebra in the framework of interacting boson model. Also, we perturbed this Hamiltonian in the version 2 with adding a new term, the O(6) Casimir operator, due to the nature of these intruder states. The results confirm the accuracy of this mixing configuration in the description of all considered energy levels and especially, the intruder states. Also, these results suggest same approach with adding other Casimir operators of different symmetry chains to extend the ability of this transitional Hamiltonian.

Intensified gas-liquid mixing in bioreactors equipped with a dual coaxial mixer containing biopolymer solutions

One of the significant challenges in the efficient operation of bioreactors is uniform gas dispersion in very viscous non-Newtonian fluids because of the complex rheology exhibited by these fluids. The uneven gas distribution is more pronounced when large-scale aerated bioreactors with aspect ratios of higher than one are utilized. Prior studies have shown that using a close clearance anchor and two centrally positioned impellers in gas-liquid coaxial mixers can improve gas dispersion in pseudoplastic fluids. Nonetheless, despite the extensive applications of yield-pseudoplastic fluids in many industries, no research has been conducted on the gas dispersion in yield-pseudoplastic fluids within a dual coaxial bioreactor with a greater-than-one aspect ratio. In this regard, electrical resistance tomography (ERT) and computational fluid dynamics (CFD) were employed to assess the effect of operating parameters, namely central impeller speed, anchor speed, aeration rate, rotating mode, and pumping mode of central impeller on the aeration efficiency in yield-pseudoplastic fluids. The experimental measurement of the overall gas hold-up affirmed the profound impact of using a close clearance anchor. Even though the down-pumping and co-rotational mode at Na = 30 rpm provided the highest aeration efficiency, more uniform gas dispersion was observed at Na = 10 rpm owing to a greater axial velocity in the downward direction and more effective circulation loops. Compared to the downward pumping direction, lower gas hold-up values were obtained for the up-pumping configurations. Finally, the superiority of the down-pumping and co-rotational mode was demonstrated by comparing the aeration efficiency of various mixing configurations.

Effect of mixing section configurations on combustion efficiency of Mg-CO2 Martian ramjet

Experiments were conducted to determine the effects of the mixing section configurations on the Mg-CO2 Martian ramjet combustion efficiency. It was carried out at a mainstream mass flow rate of 110 g/s and a temperature of 810 K. The chamber pressure was measured under different configurations and Oxidizer to Fuel (O/F) ratios. Results showed that the engine achieved self-sustaining combustion and worked stably during experiments. The pre-combustion chamber is needed to increase the combustion efficiency and promote the full combustion of the powder. After the configuration of the pre-combustion chamber, the best combustion efficiency reached 80% when radial powder injection and lateral carbon dioxide intake were used. In addition, the O/F ratio in the pre-combustion chamber decreased from 0.67 to 0.31, resulting in an 8% increase in the combustion efficiency. It was speculated that different mixing section configurations and the variations in an O/F ratio within the pre-combustion chamber impacted the combustion efficiency and in essence, all affected the flow velocity and residence time of the two-phase flow in the combustion chamber.

Influence of Centrifugation and Shaking on the Self-Assembly of Lysozyme Fibrils.

Protein self-assembly into fibrils and oligomers plays a key role in the etiology of degenerative diseases. Several pathways for this self-assembly process have been described and shown to result in different types and ratios of final assemblies, therewith defining the effective physiological response. Known factors that influence assembly pathways are chemical conditions and the presence or lack of agitation. However, in natural and industrial systems, proteins are exposed to a sequence of different and often complex mass transfers. In this paper, we compare the effect of two fundamentally different mass transfer processes on the fibrilization process. Aggregation-prone solutions of hen egg white lysozyme were subjected to predominantly non-advective mass transfer by employing centrifugation and to advective mass transport represented by orbital shaking. In both cases, fibrilization was triggered, while in quiescent only oligomers were formed. The fibrils obtained by shaking compared to fibrils obtained through centrifugation were shorter, thicker, and more rigid. They had rod-like protofibrils as building blocks and a significantly higher β-sheet content was observed. In contrast, fibrils from centrifugation were more flexible and braided. They consisted of intertwined filaments and had low β-sheet content at the expense of random coil. To the best of our knowledge, this is the first evidence of a fibrilization pathway selectivity, with the fibrilization route determined by the mass transfer and mixing configuration (shaking versus centrifugation). This selectivity can be potentially employed for directed protein fibrilization.

NLO results with operator mixing for fully heavy tetraquarks in QCD sum rules

We study the mass spectra of overline{Q}Qoverline{Q}Q (Q = c, b) systems in QCD sum rules with the complete next-to-leading order (NLO) contribution to the perturbative QCD part of the correlation functions. Instead of meson-meson or diquark-antidiquark currents, we use diagonalized currents under operator renormalization. We find that differing from conventional mesons overline{q}q and baryons qqq, a unique feature of the multiquark systems like overline{Q}Qoverline{Q}Q is the operator mixing or color configuration mixing induced by NLO corrections, which is crucial to understand the color structure of the states. Our numerical results show that the NLO corrections are very important for the overline{Q}Qoverline{Q}Q system, because they not only give significant contributions but also reduce the scheme and scale dependence and make Borel platform more distinct, especially for the overline{b}boverline{b}b in the overline{textrm{MS}} scheme. We use currents that have good perturbation convergence in our phenomenological analysis. With the overline{textrm{MS}} scheme, we get three JPC = 0++ states, with masses {6.35}_{-0.17}^{+0.20} GeV, {6.56}_{-0.20}^{+0.18} GeV and {6.95}_{-0.35}^{+0.21} GeV, respectively. The first two seem to agree with the broad structure around 6.2 ~ 6.8 GeV measured by the LHCb collaboration in the J/ψJ/ψ spectrum, and the third seems to agree with the narrow resonance X(6900). For the 2++ states we find one with mass {7.03}_{-0.26}^{+0.22} GeV, which is also close to that of X(6900), and another one around {7.25}_{-0.35}^{+0.21} GeV, which has good scale dependence but slightly large scheme dependence.

Asymmetric encryption by optical Kerr nonlinearities exhibited by electrochromic NiO thin films.

Herein is analyzed how an electric field can induce a band gap shift in NiO films to generate an enhancement in their third-order optical nonlinearities. An electrochromic effect seems to be responsible for changes in absorbance and modification in off-resonance nonlinear refractive index. The optical Kerr effect was determined as the dominant physical mechanism emerging from the third-order optical susceptibility processes present in a nanosecond two-wave mixing configuration at 532 nm wavelength. Absence of any important multi-photonic absorption was validated by the constant trace of high-irradiance optical transmittance in single-beam mode. The inspection of nonlinear optical signals allowed us to propose an exclusive disjunctive logic gate assisted by an electrochromic effect in an optical Kerr gate. Asymmetric encryption by our XOR system with the influence of a switchable probe beam transmittance and electrical signals in the sample was studied. Immediate applications for developing multifunctional quantum systems driven by dynamic parameters in electrochromic and nonlinear optical materials were highlighted.

Insight into co-pyrolysis interaction of Pingshuo coal and low-density polyethylene under varied mixing configurations via in-situ Py-TOF-MS

The real-time detection of volatiles is crucial for exploring co-pyrolysis mechanisms. In this study, the co-pyrolysis interaction mechanism of Pingshuo coal (PC) and low-density polyethylene (LDPE) with three varied mixing configurations was explored based on the product distribution and stable radicals in char by using in-situ pyrolysis time-of-flight mass spectrometry with vacuum ultraviolet photoionization as well as electron paramagnetic resonance. Total ion currents results show that mixing configurations have an obvious impact on the release of volatiles. In the coal-LDPE test, the volatiles from coal promotes the cracking of long-chain branches in LDPE, resulting in high alkenes content. Meanwhile, the LDPE melts delay the release of coal volatiles causing a higher peak temperature of 478 °C. As for the LDPE-coal configuration, the LDPE volatiles has a better hydrogen-donor effect, which can interact with volatiles and char from coal pyrolysis to facilitate the formation of aromatics and phenols. Comparatively, coal/LDPE configuration prompts the molten LDPE to coat coal particles and exhibits poor synergies between coal and LDPE. In addition, LDPE-coal char has higher spin concentrations of C-, and O-centered radicals, indicating that the released ·H radicals from LDPE pyrolysis can well interact with char and unreleased volatiles in coal.

Power Consumption Characterization of Energy-Efficient Aerated Coaxial Mixers Containing Yield-Stress Biopolymer Solutions

The operations of mixing systems utilized in a variety of industrial applications for dispersing gas in non-Newtonian fluids are complex. The main challenge is to maintain a homogeneous medium throughout the vessel. In fact, coaxial mixers have demonstrated an energy-efficient performance for systems containing rheologically complex fluids. However, the accurate characterization of the power demand for gas dispersion in yield-stress fluids using coaxial mixers remains unclear. Hence, the objective of the present work was to investigate the power characteristics of a coaxial mixing system comprising the xanthan gum solution, which is a shear-thinning fluid possessing yield stress. The power consumption of an Anchor-PBT mixing configuration was measured experimentally at different central and anchor impeller speeds, rotation modes, and aeration rates. The main effects of the operating variables and their interactions were quantified using a central composite design of experiments. Significant effects of the central impeller speed and the interaction between the anchor speed and the aeration rate were identified. Also, a generalized power curve for this mixing system was proposed based on a predefined equivalent impeller speed and impeller diameter expressions to develop the novel power number and Reynolds number. The findings of this work provide an asset in designing and scaling up of energy-efficient aerated coaxial mixers by rapidly estimating the power demand.