Mixing Index Research Articles

New sexually transmitted HIV infections from 2016 to 2050 in Guangdong Province, China: a study based on a dynamic compartmental model

BackgroundIn Guangdong Province, China, there is lack of information on the HIV epidemic among high-risk groups and the general population, particularly in relation to sexual transmission, which is a predominant route. The new HIV infections each year is also uncertain owing to HIV transmission from men who have sex with men (MSM) to women, as a substantial proportion of MSM also have female sexual partnerships to comply with social demands in China.MethodsA deterministic compartmental model was developed to predict new HIV infections in four risk groups, including heterosexual men and women and low- and high-risk MSM, in Guangdong Province from 2016 to 2050, considering HIV transmission from MSM to women. The new HIV infections and its 95% credible interval (CrI) were predicted. An adaptive sequential Monte Carlo method for approximate Bayesian computation (ABC-SMC) was used to estimate the unknown parameter, a mixing index. We calibrated our results based on new HIV diagnoses and proportions of late diagnoses. The Morris and Sobol methods were applied in the sensitivity analysis.ResultsNew HIV infections increased during and 2 years after the COVID-19 pandemic, then declined until 2050. New infections rose from 8,828 [95% credible interval (CrI): 6,435–10,451] in 2016 to 9,652 (95% CrI: 7,027–11,434) in 2019, peaking at 11,152 (95% CrI: 8,337–13,062) in 2024 before declining to 7,084 (95% CrI: 5,165–8,385) in 2035 and 4,849 (95% CrI: 3,524–5,747) in 2050. Women accounted for approximately 25.0% of new HIV infections, MSM accounted for 40.0% (approximately 55.0% of men), and high-risk MSM accounted for approximately 25.0% of the total. The ABC-SMC mixing index was 0.504 (95% CrI: 0.239–0.894).ConclusionsGiven that new HIV infections and the proportion of women were relatively high in our calibrated model, to some extent, the HIV epidemic in Guangdong Province remains serious, and services for HIV prevention and control are urgently needed to return to the levels before the COVID-19 epidemic, especially in promoting condom-based safe sex and increasing awareness of HIV prevention to general population.

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

The challenge of mixing high-viscosity materials is a common issue encountered in the manufacturing process of food materials. The advantages of the internal meshing screw mixer have led to its adoption in various manufacturing processes, but it has yet to be implemented in the food industry. The paper presents a design method for an internal meshing screw mixer based on kinematic principles. The mixer features a helical chamber created by alternating volumes formed by the stator and rotor, establishing an extension-dominated environment for mixing high-viscosity fluids. A kinematic model based on the internal cycloid principle was established, providing trajectories and equations for key points on the rotor, simulating both its rotation and revolution processes, and revealing the velocity variations at different points on the rotor. Based on the kinematic analysis results, a stator and rotor design method was developed according to relevant functional divisions. To achieve the desired motion effects, transmission and support devices were designed, and the relationship between the transmission device and the internal cycloid surface of the fixed rotor was established. The mixer’s application and mixing effectiveness in the food industry were validated using corn syrup and flour. Experimental results showed that the extensional mixer described in the paper effectively mixed high-viscosity fluids while also efficiently blending fine powders. Slurry viscosity was tested with a rheometer at different speeds with an eccentric rotor mixer. Results showed that viscosity decreased with increasing shear rate, with a more pronounced decrease at higher shear rates. The apparent viscosity trend remained consistent at different speeds, although variations were observed at lower shear rates, especially concerning speed. The non-Newtonian fluid index exhibited minimal variations at different speeds, while the consistency coefficient showed significant fluctuations. The mixing uniformity index of the slurry was used to evaluate the mixing uniformity and dispersion uniformity of this extensional mixer. At different rotational speeds, the density of the slurry changes little. The uniformity index of mixing decreases gradually with the increase of rotational speed, reaching its maximum at 15 r/min. The overall trend of the uniformity index decreases with increasing rotational speed, indicating a decrease in density uniformity. A peak appears at 45 r/min, possibly due to the maximum values of elongation rate and shear rate at this speed. As the rotational speed increases, the residence time of the material in the mixer decreases, which may be the main reason for the decrease in mixing uniformity. These findings provide valuable insights into the design and utilization of extension-dominated screw mixers within the food industry, laying a solid foundation for future research and practical applications in this field.

CFD-DEM mixing of rod-like and spherical particles in fluidized beds

Understanding the behavior of particle mixing in fluidized beds is crucial for enhancing process design. This article focuses on investigating the effect of key parameters, such as volume fraction of spherical particles, length of rod-like particles, and aspect ratio of rod-like particles, on the mixing of binary mixtures containing spherical and rod-like particles. The study employs a computational approach which couples the computational fluid dynamics and discrete element method (CFD-DEM) to explore mixing behavior of particles. Non-spherical particles are modeled using the multi-sphere method. A combination of qualitative and quantitative approaches is employed to assess the mixing performance, including visual examination of the fluidized bed and calculation of the subdomain-based mixing index. It was shown that an increase in rod-like particle length, aspect ratio, and volume fraction of rod-like particles weaken the mixing. Furthermore, the quality of mixing is directly influenced by bubble size and particle granular temperature. This study offers valuable insights into the mixing behavior of rod-like and spherical particles, contributing to the design and optimization of binary fluidization processes.

Development and Validation of the Bone Tumor Surgery Complexity Score

Bone tumors often manifest with non-specific symptoms such as pain and swelling, often posing diagnostic challenges. Optimal treatment requires centralized care in specialized centers, emphasizing the need for complete tumor removal and interdisciplinary collaboration. We developed the Bone Tumor Surgery Complexity Score (BT-SCS) based on a retrospective study of 501 patients. The BT-SCS, structured around patient demographics, tumor biology, and surgical parameters, categorizes surgical cases into four groups to comprehensively assess complexity. Application of the BT-SCS resulted in scores ranging from 3 to 33, with an average score of 14 ± 7.2. Patients with malignant tumors had higher scores (19.6 ± 5.2) compared to those with benign (10.0 ± 3.8) or intermediate malignant tumors (14.6 ± 7.1). Patients with pelvic tumors registered the highest scores (16.0), followed by extremities/trunk (14.3) and spinal tumors (13.6). The BT-SCS was validated against the Case Mix Index (CMI), using an independent cohort of bone and soft tissue cases. This validation process, utilizing Loess smoothing, illustrated the BT-SCS’s granular differentiation of surgical complexity, particularly in the lower-to-mid-range of case severities. The BT-SCS represents a significant shift from volume-based to complexity-based assessments in surgical care, aligning with evolving healthcare paradigms. It serves as a tool for strategic patient allocation to treatment centers, aiming to improve outcomes and benchmarking in sarcoma care. The score’s development and application in clinical practice align with the focus on patient-centered and value-based healthcare. Future enhancements, including machine learning integration and outcome data, will refine its categorization process, enhancing clinical utility.

Experimental and numerical assessment and performance optimization of a novel T-arrow microfluidic device to mix two fluids with different thermophysical properties

Micromixers are critical parts of integrated microfluidic systems and their performance improvement has been a crucial problem for many investigators. Since the mixing enhancement in passive micromixers is hindered by the low-Reynolds number regime, multiple inlets have been recommended to create chaotic advection and improve the mixing quality. In this paper, a novel T-arrow micromixer is introduced to augment the mixing index (MI) of two liquids with different thermophysical properties. Numerical and experimental investigations are carried out by changing the distance between the inlets (a), the angle of the arrow-shaped inlet (α), the velocity ratio (VR), and the width-to-height aspect ratio (AR). Five optimization algorithms are also utilized to optimize the micromixer performance to achieve the most appropriate geometrical characteristics. It is found that MI is enhanced significantly by adding a Y-type inlet compared to a T-shaped mixer. The results demonstrate that while MI declines with a, there are optimal values for α, VR, and AR. Besides, parallel optimization of MI and pressure drop recommends two optimal micromixers with mixing energy cost (MEC) of 2841 Pa and 3370 Pa.

The association between mixed exposure to per- and polyfluoroalkyl substances (PFAS) and the risk of diabetes

IntroductionThis study aims to investigate the relationship between exposure to per- and polyfluoroalkyl substances (PFAS) and the risk of diabetes by analyzing a large dataset from the National Health and Nutrition Examination Survey (NHANES).Material and methodsThis study analyzed data from the US NHANES database from 2003 to 2018. Generalized linear regression models were used to examine the relationship between serum chemical concentrations and diabetes. Weighted quantiles and regression were employed to assess the association between mixed chemical exposure and diabetes. The 'mixture effect' between chemicals and diabetes was estimated using a Quantile g-Computation model.ResultsThe study involved 11,780 participants, with 1,451 individuals having diabetes and 10,329 being non-diabetic. Logistic regression analysis was to investigate the relationship between five PFAS chemicals and the diabetes risk, while controlling for all covariates. The results indicated that none PFAS chemicals exhibited a statistically significant association with an increased risk of diabetes. However, when exploring the positive and negative constraint models of the Weighted Quantile Sum (WQS), the coefficient of the chemical mixing index displayed a strong correlation with diabetes in model III, even after adjusting for covariates. Additionally, an evaluation of the 'mixture effect' using Quantile g-computation revealed that among the five chemicals, the combined exposure effect of Perfluorononanoate (PFNA) on diabetes was positive, whereas exposure to the other four chemicals had a negative impact.ConclusionsThe study findings suggest a possible connection between PFAS and an increased risk of diabetes, particularly highlighting PFNA's positive correlation with the combined exposure effect on diabetes.

The Effect of Built Environment on Carbon Emission from Travel Behavior in the City center of Surabaya

Climate change is currently demanding attention due to global warming caused by increased Greenhouse Gas (GHG) emissions from the land transportation sector. The built environment is one of the factors that can influence non-motorized travel and emissions production. The built environment is identified using the 3D component approach (Density, Diversity, Design). The City center of Surabaya area is one of the Central Business Districts (CBDs) that is not exempt from emission issues and has the potential to decrease emissions through environmental arrangement scenarios. This research investigates the correlation between the 3D components and carbon emission production using the method of correlation analysis and multiple linear regression. The analysis results show a significant correlation between carbon emission production and the travel behavior of the city center of the Surabaya area community. Travel behavior variables influencing carbon emission production are household income, vehicles ownership, and travel distance. Furthermore, the study results indicate a significant relationship between travel behavior and the 3D components, as well as a significant association between the 3D components and carbon emission production. The 3D components that affect carbon emission production are population density, land use mix index, and pedestrian pathway density.

Study on the segregation effect of pyrite and brass ore particles under combined pendulum vibration

This article uses a combined pendulum mode to study the segregation behavior of spherical particles of pyrite and brass ore with different diameters using the discrete element method. The numerical simulation program includes extensive oscillation tests on binary mixed particles of pyrite and brass ore spherical particles in different steel U-shaped oscillation grooves, different oscillation frequencies, oscillation angles, and particle sizes. The dispersion coefficient γ calculated from the Lacey mixing index M is used to characterize the segregation behavior of binary mixed particles and track the evolution of segregation. Numerical simulation shows that the oscillation frequency is 8 Hz, the oscillation amplitude is 14°, and the dispersion coefficient γ of the first group with protrusions reaches 0.8, which is about 19.4% higher than the dispersion coefficient 0.67 of the first group with light grooves. The dispersion coefficient γ of the second group with added protrusions reached 0.69, which is about 16.95% higher than the dispersion coefficient 0.59 of the second group when using a light groove. The addition of protrusions improved the particle layering effect. The oscillation amplitude is taken as 14°, and the oscillation frequencies are taken as 6Hz, 8Hz, 10Hz, and 12Hz, respectively. As the oscillation frequency increases, collisions between particles become more intense, and the dispersion coefficient γ between particles increases to a certain extent when it changes from 6Hz to 8Hz. Then, as the oscillation frequency increases, the dispersion coefficient γ decreases in severe fluctuations, and the particle stratification effect actually deteriorates. The oscillation frequency is taken as 8Hz, and the oscillation amplitude is taken as 10°, 14°, and 18°, respectively. After the oscillation amplitude increases to 14°, the dispersion coefficient γ of the particles remains basically stable, and changing the oscillation amplitude has almost no effect on the particle stratification effect. The oscillation frequency is 8Hz, and the oscillation amplitude is 14°. When adding protrusions to the steel U-shaped oscillation groove, the average relative errors of both experimental schemes are less than 1%, and the correlation coefficients are close to 1. The data points are very close to the 45° line. It indicates that the experimental data and simulation values have high consistency, and the discrete element method is feasible and reliable as a method for studying mineral particulate matter. The in-depth study of the separation and stratification behavior of ore particles under combined oscillation is of great scientific significance for the development of new combined vibration equipment.

Numerical and experimental investigation of chaotic advection and diffusion mixing effects in 3D multihelical microfluidics for liposome synthesis

The recent advances in nanomaterials’ production by microfluidics with high throughput became critical for industry-scale production. Numerical simulation has been part of this development, allowing faster and more detailed study of the process that would be costly only experimentally. Here, we investigated the diffusion and chaotic advection effects on cationic and stealth liposome production in a 3D multihelical chaotic-advection microfluidic device. Suitable conditions for chaotic advection were primarily investigated with computational fluid dynamics (CFD) assessing diverse flow rate ratio (FRR) and total flow rate (TFR). The results showed that Reynolds ≈ 100 and Dean number > 50 can trigger chaotic advection for this device, corresponding to a TFR of 5 mL/min. We produced the liposomes in the same conditions as the simulations to evaluate the impact of these parameters on the colloidal physicochemical properties. A clear difference was shown between TFR ≤ 1 and TFR ≥ 5 mL/min for size and polydispersity (PDI). An increase in PDI was observed for FRR 10, in which the mixing index (M.I.) played an important role. The effect of composition proved an important factor, as stealth liposomes were not deeply affected by TFR change. Cryo-Transmission Electron Microscopy (Cryo-TEM) analysis showed that both cationic and stealth liposomes resulted in unilamellar liposomes. Coupling numerical simulation with experimental characterization proved an efficient process evaluation in microfluidics. Finally, the high mass throughput (2.8 g/h) with the chaotic advection microfluidic device shows a potential microchip for industrial scale-up and parallelization.

Shape-dependent size polydispersity: DEM investigation of mixing behavior in a vibrating packed bed system

The Discrete element method is applied to examine the influence of shape-dependent size polydispersity on mixing behavior in a vibrating packed bed system. A series of tests for optimized simulation settings for evaluation of mixing are performed. The influence of size polydispersity (standard deviation to mean particle diameter ratio) and the particle shape on mixing is assessed using the overall mixing index. The mixtures are differentiated between homogeneous and heterogeneous mixtures. In homogeneous mixtures, continuous (Gaussian) distribution outperforms discrete (binary and ternary). Mixing decreases with size polydispersity transitioning from narrow to wide distributions in homogeneous Gaussian mixtures. For heterogeneous Gaussian mixtures, the mixing trends for fine particle shapes are ellipsoid > sphere > cylinder > cube, while the mixing trends for coarse particle shapes are cylinder > sphere > ellipsoid > cube. Changing intermediate particle shapes in heterogeneous ternary mixtures impacts mixing; the cube shows worst performance.

A mixing index for uniformly and gap-graded cohesionless particles influenced by mixing rate and diameter of stirring rods

Soil mechanics, sometimes, deals with the mixing of soil such as in deep mixing of soil and mixing of soil in tunnel boring machines, i.e., earth pressure balance (EPB-TBM) shields. The geometry of mixing apparatus such as size of stirring rods plays an important role to achieve higher degree of mixing. Moreover, the effect of gap-graded particles being mixed on degree of mixture should also be evaluated. It is important to estimate the extent of mixing of the soil to confirm the required performance of such phenomenon.This study aims to propose a simple method to quantify the degree of mixture of solid particles stirred by rotation of rods with varying diameters at different mixing rates. Discrete element method (DEM) is used to simulate the stirring process and evaluate the degree of mixture at each rotation based on the spatial distribution of different types of particles. To reduce complexity in the mixing process of particles, this study focuses on monodispersed (i.e., uniformly graded) and bidispersed (i.e., narrowly gap-graded) spherical particles where inter-particle cohesion is not considered. The DEM results reveal spatial variation of the degree of mixture (dm) in the given volume; however, its mean (dm¯) increases with the rotation number of stirring rods. Besides, dm¯ depends on the size of stirring rods whereas the mixing rate is less sensitive to dm¯ for the non-cohesive sandy particles. The dm¯ of narrowly gap-graded particles cases is slightly on the lower side as compared to that of uniformly graded particles. The results of the DEM simulations are validated through the model test.

Multi-objective optimization of expansion-contraction micromixer using response surface methodology: A comprehensive study

This study provides a comprehensive analysis of the optimization of micromixers, highlighting their critical role in improving the effectiveness of chemical reactions and fluid mixing processes at a small scale. Employing OpenFOAM, we optimized the geometry of a micromixer comprised of multiple expansion-contraction segments across a Reynolds number range from 0.1 to 100. We established three design variables, P1, P2, and P3, to modify the geometry of each contraction-expansion segment to maximize the overall performance of the micromixer. Our experimental design utilized the optimal space-filling method, followed by the application of the genetic aggregation method to the generated sample to yield response surfaces. Two distinct optimization strategies were implemented following the verification of the response surfaces’ accuracy. The first focused on maximizing the mixing index, while the second aimed to increase the mixing index and reduce the pressure difference simultaneously. A subsequent sensitivity analysis revealed significant relationships between the design variables and objective parameters. Key findings include achieving maximum MI increases of 26.26 % and 23.06 % at Re values of 10 and 100, respectively, and the role of recirculation zones and chaotic convection in enhancing mixing, especially at Re = 100. Furthermore, a comparative analysis with other micromixer optimization studies demonstrated the superiority of the present study, particularly in reducing pressure difference, thereby enhancing overall mixer performance.

The value of admission avoidance: cost-consequence analysis of one-year activity in a consolidated service.

Many advantages of hospital at home (HaH), as a modality of acute care, have been highlighted, but controversies exist regarding the cost-benefit trade-offs. The objective is to assess health outcomes and analytical costs of hospital avoidance (HaH-HA) in a consolidated service with over ten years of delivery of HaH in Barcelona (Spain). A retrospective cost-consequence analysis of all first episodes of HaH-HA, directly admitted from the emergency room (ER) in 2017-2018, was carried out with a health system perspective. HaH-HA was compared with a propensity-score-matched group of contemporary patients admitted to conventional hospitalization (Controls). Mortality, re-admissions, ER visits, and direct healthcare costs were evaluated. HaH-HA and Controls (n = 441 each) were comparable in terms of age (73 [SD16] vs. 74 [SD16]), gender (male, 57% vs. 59%), multimorbidity, healthcare expenditure during the previous year, case mix index of the acute episode, and main diagnosis at discharge. HaH-HA presented lower mortality during the episode (0 vs. 19 (4.3%); p < 0.001). At 30 days post-discharge, HaH-HA and Controls showed similar re-admission rates; however, ER visits were lower in HaH-HA than in Controls (28 (6.3%) vs. 34 (8.1%); p = 0.044). Average costs per patient during the episode were lower in the HaH-HA group (€ 1,078) than in Controls (€ 2,171). Likewise, healthcare costs within the 30 days post-discharge were also lower in HaH-Ha than in Controls (p < 0.001). The study showed higher performance and cost reductions of HaH-HA in a real-world setting. The identification of sources of savings facilitates scaling of hospital avoidance. ClinicalTrials.gov (26/04/2017; NCT03130283).

Process intensification of a catalytic-wall Taylor-Couette reactor through unconventional modulation of its angular speed

This study proposes a non-conventional operation of a Taylor-Couette reactor by introducing a periodic flow perturbation as a modulated angular velocity of its inner cylinder. The applicability of this type of waveform has yet to be explored in Taylor-Couette reactors as a means to enhance mass transfer phenomena in reactive systems. A multiphysics numerical study was carried out considering a mass-transfer limited system with a catalytic reaction at the outer cylinder boundary of the reactor while applying different modulations of the inner cylinder angular speed. Results showed that a modular signal could yield conversions similar to a constant angular-speed operation. However, the use of modulating signals brings two essential benefits. First, it enhances mass transfer, which yields higher conversions by dynamically changing the flow patterns in the reactor. This improvement is demonstrated and discussed in terms of a dynamic mixing index, which accounts for the formation and abrupt disruption of Taylor vortices in the reactor. Second and more importantly, this type of operation leads to an overall reduction in the average electrical power required to drive the system (∼25 % reduction). The present study opens the possibility of using intelligent control strategies to optimize reactions and intensify conventional systems with non-conventional operation modes.

Identifying intrusion of seawater in coastal aquifers by modified GALDIT (M-GALDIT) index

Contamination of coastal aquifers by seawater intrusion (SWI) is a major environmental problem. A modified GALDIT method (M-GALDIT), and multi-criteria decision model AHP has been used to identify regions vulnerable to seawater intrusion. We have used the groundwater suitability index for seawater intrusion (GQISWI) in estimating the M-GALDIT index. While the GALDIT analysis indicates that ∼28% of the area is moderately vulnerable, and 8% of the area is relatively highly vulnerable, our estimates using AHP and M-GALDIT method indicate ∼19% of the area as moderately vulnerable, ∼22% of the area as relatively highly vulnerable zones. The GQISWI values in the region vary between 0 and 96.96, indicating that most of the groundwater samples belong to mixed water types. Faults and fractures, population distribution, water-rock interaction, ionic exchange reactions, and evaporation appear to be the dominant mechanisms, besides seawater intrusion that control the overall groundwater geochemistry in the region. Ca2+-HCO3-, Ca2+-Na+-HCO3−, and Ca2+-Mg2+-Cl− are the most dominant water types in the study area. The seawater mixing index (SMI) reveals that ∼34.5% of samples are of relatively freshwater types, whereas ∼61% of samples appear contaminated to some extent, presumably due to the mixing of seawater, or anthropogenic activities such as mining, agricultural activities, etc. Furthermore, analysis of the HFE-D diagram indicates that ∼23% of samples are directly affected by seawater intrusion.

Outcomes of Chengdu Pediatric Emergency Triage Criteria: A Retrospective Study of 198,628 Pediatric Patient Records.

BACKGROUND The Chengdu pediatric emergency triage criteria were developed at our hospital and consist of 4 triage levels: immediate treatment (level 1), treatment within 10 min (level 2), treatment within 30 min (level 3), and treatment within 240 min (level 4). This study aimed to evaluate outcomes from the levels 1 to 4 of this triage criteria. MATERIAL AND METHODS A self-designed survey form was used to collect pediatric Emergency Department (ED) patients' general data, including age, sex, and chief concern, and clinical data, including triage level, whether the patient had died, and whether the patient was admitted to our hospital. A total of 198,628 patient records that were triaged during January to May 2022 using Chengdu pediatric emergency triage criteria were included in this retrospective study. The numbers of patients triaged to levels 1, 2, 3, and 4 were 128, 1164, 14,560, and 182,776, respectively. RESULTS Statistically significant differences were found in waiting time for treatment, hospital admission rates, admission conversion rates, and case mix index at admission under different triage levels. The higher the triage priority level, the shorter the waiting time for ED treatment, higher the hospital admission and admission conversion rates, and higher case mix index value. CONCLUSIONS The Chengdu pediatric emergency triage criteria developed and applied within our hospital appears to be characterized by good clinical validity. Equipped with this triage criteria, triage nurses are more capable of determining the severity and emergency of the pediatric ED patients' health conditions and effectively triaging the patients.

Chemical properties and single-particle mixing state of soot aerosol in Houston during the TRACER campaign

Abstract. A high-resolution soot particle aerosol mass spectrometer (SP-AMS) was used to selectively measure refractory black carbon (rBC) and its associated coating material using both the ensemble size-resolved mass spectral mode and the event trigger single particle (ETSP) mode in Houston, Texas, in summer 2022. This study was conducted as part of the Department of Energy Atmospheric Radiation Measurement (ARM) program's TRacking Aerosol Convection interactions ExpeRiment (TRACER) field campaign. The study revealed an average (±1σ) rBC concentration of 103 ± 176 ng m−3. Additionally, the coatings on the BC particles were primarily composed of organics (59 %; 219 ± 260 ng m−3) and sulfate (26 %; 94 ± 55 ng m−3). Positive matrix factorization (PMF) analysis of the ensemble mass spectra of BC-containing particles resolved four distinct types of soot aerosol, including an oxidized organic aerosol (OOABC,PMF) factor associated with processed primary organic aerosol, an inorganic sulfate factor (SO4,BC,PMF), an oxidized rBC factor (O-BCPMF), and a mixed mineral dust–biomass burning aerosol factor with significant contribution from potassium (K-BBBC,PMF). Additionally, K-means clustering analysis of the single-particle mass spectra identified eight different clusters, including soot particles enriched in hydrocarbon-like organic aerosol (HOABC,ETSP), sulfate (SO4,BC,ETSP), two types of rBC, OOA (OOABC,ETSP), chloride (ClBC,ETSP), and nitrate (NO3,BC,ETSP). The single-particle measurements demonstrate substantial variation in BC coating thickness with coating-to-rBC mass ratios ranging from 0.1 to 100. The mixing state index (χ), which denotes the degree of homogeneity of the soot aerosol, varied from 4 % to 94 % with a median of 40 %, indicating that the aerosol population lies in between internal and external mixing but has large temporal and source type variability. In addition, a significant fraction of BC-containing particles, a majority enriched with oxidized organics and sulfate, exhibit sufficiently high κ values and diameters conducive to activation as cloud nuclei under atmospherically relevant supersaturation conditions. This finding bears significance in comprehending the aging processes of rBC-containing particles and their activation into cloud droplets. Our analysis highlights the complex nature of soot aerosol and underscores the need to comprehend its variability across different environments for accurate assessment of climate change.

Numerical investigation of mixing performance for a helical tangential porous tube-in-tube microchannel reactor

The tube-in-tube microchannel reactor (TMCR) is widely applied in chemical engineering and material industries. Two or more fluids are mixed in the annular channel of TMCR. This work aims to introduce a helical tangential porous tube-in-tube microchannel reactor (HTP-TMCR). The performance of HTP-TMCR is analyzed using computational fluid dynamics (CFD) method, focusing on three aspects: mixing index, pressure drop, and velocity distribution. Additionally, this study investigates the impacts of four geometric parameters, including left and right helical directions, pitch, pore size, and length of the non-porous zone, on the mixing performance of HTP-TMCR. The simulation results reveal that the mixing index initially decreases as the flow rate increases, reaching its lowest point (approximately 75%) at Q=2 L/h. Subsequently, there is a sharp rise to a second inflection point at Q=10 L/h, followed by a gradual progression stabilizing around 95%. Specifically, the left helical configuration demonstrates superior performance compared to the right one. Optimal mixing is achieved at low flow rates when the pitch is 4 mm and the pore size is 0.4 mm. Designing the length of the non-porous zone to be 5 mm is recommended. Furthermore, the characteristic of pressure drop for HTP-TMCR indicates its potential for commercial applications.

Evaluation of the mixing index in a micromixer of side feeds in a conical chamber

This study delves into the investigation of mixing efficiency in microdevices by augmenting angular momentum within a truncated cone-shaped micromixer through side-feedings. While microchannel flows are typically dominated by molecular transport, characterized by parallel streamlines, this hinders rapid responses in mixing quality. To address this, we evaluate a micromixer featuring side-feedings coupled to a 2D truncated cone, followed by a wavy microchannel. The research assesses the impact of feed arrangement in the entrance section, Reynolds number (Re), and the curvatures of bumps in the wavy microchannel. Symmetrical lateral feeds promote homogeneous mixing in the inlet section where streamlines intersect. At the device outlet, all bump curvatures contribute to a mixing index exceeding 0.90 within a Reynolds number range of 20 to 40. Additionally, lower Reynolds numbers (Re = 0.1) yield a mixing index above 0.90, but with a slower and predominantly diffusive flow. Notably, a sharper curvature geometry results in smaller pressure drops while maintaining a comparable mixing index to other geometries, indicating it as a promising choice for bump curvature.

Performance simulation of a dual-channel micro-mixer

In order to investigate whether changing the relative positions of the connecting units of a micro-mixer with dual connecting units would affect the mixing performance, the group proposed a micro-mixer with dual connecting units based on previous studies. The micro-mixer consists of a T-shaped inlet, six cubic mixing chambers and a dual connection channel between the mixing chambers. Numerical simulations showed that the outlet mixing index was 40.6% when the positions of the inlet and connecting units of the micro-mixer were staggered on both sides of the horizontal center and on both sides of the vertical center. At the same flow rate, the mixing index of the first mixing unit reaches 66.4% when the inlet of the micro-mixer changes from both sides of the horizontal center to a T-shaped inlet. The increase in the mixing index suggests that the contraction-stretching dual-channel arrangement can be utilized to promote mixing by utilizing the non-equilibrium vortices generated by the diffusion displacement limitations on the side walls of the mixing unit. The mixing efficiency of the optimized model designed according to this strategy increased to 85.8%. This paper provides a new perspective for optimizing the structural design and performance enhancement of micro-mixers.