Concentration Distribution Research Articles

Novel dissolved oxygen distribution model of a full-scale aeration tank for a municipal wastewater treatment plant in a cold climate region

ABSTRACT Aeration is the most energy-intensive process in wastewater treatment plants (WWTP). Seasonal variation in hydraulic flow and load has a significant effect on WWTP's aeration energy efficiency. High flow and temperature variations are common in cold climate regions, and with climate change increasing, extreme weather events will accentuate these situations. The prediction of oxygen mass transfer is crucial for minimizing the energy consumption of the aeration tank. This study presents a computational fluid dynamics model for a turbulent flow regime, simulating the hydraulics and dissolved oxygen (DO) concentration distribution of two phases, water and air bubbles, in a full-scale, as-built activated sludge tank. Model validation error was less than 15%. Different seasonal flows and temperatures were investigated by fixing liquid side oxygen mass transfer coefficient (kL) to 0.7 × 10–5 m/s and initial bubble diameter (dB) to 0.0025 m in the gas phase. The results show that variating hydraulic flow causes noticeable differences in DO distribution and higher flow could be more effective levelling in DO gradients. More even DO distribution could result in using up to a 10% lower DO setpoint value, using 3% less air for the same treatment result, thus lowering aeration energy cost.

Bioavailability of trace metals in sediments from Daya bay nature reserve: Spatial variation, controlling factors and the exposure risk assessment for aquatic biota

Determining the ecological risk and environmental significance of trace metal bioavailability is critical for the sustainability of the marine environment and bioresources. The spatial variation, controlling factors and ecological risks of the bioavailability of trace metals (V, Cr, Ni, Cu, Zn, As, Cd and Pb) in Daya Bay sediments were analyzed using BCR sequential extraction and diffusive gradient in thin films (DGT). Differences in concentration distributions between the anthropogenic impact zone (AIZ) and the marine disturbance zone (MDZ) revealed the accumulation of anthropogenic metals in sediments, and that the ocean dynamic conditions promoted the release of bioavailable metals from nature sediments. Fine-grained sediments rich in organic matter possessed more bioavailable metals on the surface. The negative correlations between salinity and the non-residual fractions (F123) suggests that salinity has the potential to inhibit the bioavailability of trace metals. Risk assessment based on total concentrations and acid soluble fractions (F1) showed that Cd was the dominant contributing element to the potential ecological risks with 55.8 %. The evaluation via DGT-labile concentrations indicated that Cu was the element of priority concern for aquatic exposure risk with a risk probability of 7.45 %, and the joint risk probability for metal mixture toxicity was 12.27 %. The exposure risk for aquatic biota was shown as molluscs (9.37 %) > algae (6.82 %) > crustaceans (6.21 %) > invertebrates (6.07 %) > fish (2.61 %). The results provide new clues for risk assessment and management of trace metals in coastal sediments.

How ultrasonication treatment drives the interplay between lysinoalanine inhibition and conformational performances: A case study on alkali-extracted rice residue protein isolate.

Lysinoalanine (LAL) formed during alkaline extraction of rice residue protein (RRPI), which limited its application in the food industry. In this study, the influence of ultrasonication parameters (acoustic power density, ultrasound duration, and ultrasound temperature) on the inhibition of LAL formation and conformational attributes of RRPI during alkaline extraction was elucidated. The results suggested that the acoustic power density substantially modified the chemical interaction forces between RRPI molecules. At a power density of 60W/L, the ionic bonds (14.37%) and hydrophobic interactions (49.28%) reached the maximum, while hydrogen bonds (15.29%) and disulfide bonds (21.06%) reached the minimum. Moreover, acoustic power density at 60W/L caused a decrease of 18.02% and 12.2% in α-helix, and β-turn, respectively, shifting toward β-sheet, random coil, with an increase of 7.31% and 36.16%. Following ultrasonication, the protein particle size distribution curve shifted in the direction of smaller particle size, forming a relatively concentrated and uniform protein distribution. Sonication power, temperature, and time decreased the absolute value of Zeta potential. Furthermore, significant destruction in microstructure was elicited by sonication, which made the structure looser and more microparticles. Pearson correlation analysis suggested that the inhibition in the levels of LAL was most influenced by the increase of sulfhydryl groups and Zeta potential, as well as the reduction of α-helix content, in which the alteration of the total sulfhydryl group content had a great impact on the Zeta potential and the free sulfhydryl group. The principal component analysis demonstrated a notable correlation between the total sulfhydryl group and both the Zeta potential and free sulfhydryl group of RRPI.

Analytical Sensitivity Analysis and Clinical Impact Modeling of Rapigen Rapid Diagnostic Tests for Malaria.

Laboratory benchmarking allows objective analysis of the analytical performance of malaria rapid diagnostic tests (RDTs). We present the analytical detection limits of the Rapigen BIOCREDIT Malaria Ag Pf/Pv (pLDH/pLDH), the Rapigen BIOCREDIT Malaria Ag Pf (pLDH/HRPII), and two best-in-class WHO-prequalified comparator RDTs, generated using standardized panels containing recombinant antigen, invitro cultured parasites, international standards, and clinical samples. Detection limit antigen concentrations of HRP2, PfLDH, and PvLDH were determined for the Rapigen and comparator RDTs. Detection of antigens in international units (IU)/mL was also evaluated. The Rapigen Ag Pf (pLDH/HRPII) detected 3.9 and 3.9 IU/mL for PfLDH and HRP2, respectively, and the Ag Pf/Pv (pLDH/pLDH) detected 3.9 and 5.0 IU/mL for PfLDH and PvLDH, respectively. The comparator HRP2/PfLDH and HRP2/PvLDH detected 15.6 and 31.3 IU/mL for HRP2 and PfLDH and 15.6 and 50.0 IU/mL for HRP2 and PvLDH, respectively. The RDT clinical sensitivity was predicted through application of analytical detection limits to antigen concentration distributions from clinical symptomatic and asymptomatic cases. Febrile cases would be detected in a majority by both standard and Rapigen RDTs, but incremental increases in sensitivity in the Rapigen RDTs may be important for clinical cases currently missed by microscopy. Rapigen RDTs were predicted to have improved detection of asymptomatic cases and infections with parasites carrying hrp2 deletions through more sensitive PfLDH detection. Through the benchmarking and simulation of clinical sensitivity, a method for rapidly assessing the ability of new RDTs to meet clinical needs using high-sensitivity antigen distribution data is presented.

Research on single-point fast three-dimensional concentration reconstruction of a smoke plume based on the static interference infrared imaging spectroscopy system

To meet the requirements of real-time and effectiveness of three-dimensional concentration telemetry of gas clouds and address the difficulty of fast three-dimensional concentration reconstruction of single instrument smoke plumes, the paper proposes a single-point fast three-dimensional concentration reconstruction of the smoke plume based on a static interference infrared Fourier transform imaging spectrometer (ISIFTS) by using the advantages of high throughput, large field of view, high stability, and rapid detection. Based on the scanning field switching characteristics of ISIFTS, a single instrument quickly scans the dual-field map data to obtain the three-dimensional point cloud of the target scene. Combined with the three-dimensional spatial parameters of the scene, a multi-dimensional re-projection algorithm is constructed based on the Gaussian plume continuous diffusion model to simulate the concentration-path-length product (CL) image, and the measured CL image is solved by analyzing the smoke plume image spectra data. The normalized cross-correlation fitting algorithm is used to perform the optimal matching of simulated-measured CL images, and then the three-dimensional concentration distribution of the plume scene is reconstructed based on the dimension mapping relationship. The field smoke plume telemetry experiment was designed and carried out, and the three-dimensional concentration distribution of plume gas at three emission points in the scene was obtained. The CO2 emission rates were calculated to be 13.572 kg / s, 12.225 kg / s, and 14.114 kg / s, respectively. The data are consistent with the emission rate of the coal-fired thermal power plant, which verifies the effectiveness of the single-point fast three-dimensional concentration reconstruction of the smoke plume method based on the ISIFTS system.

Navigating the Diagnostic Challenges in Lymph Node Cytology: The Case of Reactive Hyperplasia.

Fine needle cytology (FNC) is a pivotal diagnostic tool for distinguishing between benign and malignant lymphadenopathies mainly because of its minimal invasiveness, cost-effectiveness and accuracy. A major requirement for maximising diagnostic accuracy is proper sample management of aspirated cellular material. In this diagnostic process, the morphological evaluation of adequate smears is paramount, guiding cytopathologists in the selection of appropriate ancillary tests through the recognition of cell size and patterns of distribution. Here, we describe a peculiar 'concentric ovals distribution pattern', frequently observed in the FNC of benign reactive lymph nodes, which may represent an aid in the cytological diagnosis of reactive hyperplasia.

Analysis of microplastic behaviors in river-type lakes using a quasi-three-dimensional microplastic transport model

Paldang Lake in South Korea is a river-type lake characterized by weak temperature stratification and a short water residence time. It exhibits complex flow structures resulting from the convergence of two major rivers, the North Han River (NHR) and the South Han River (SHR), and one small river, the Gyeongan Stream. Analyzing the spatio-temporal variations in microplastic (MP) concentration in Paldang Lake is important because of its significance as a water supply source for the metropolitan area. In this study, a quasi-three-dimensional MP transport model (MPT-Q3D) based on the Lagrangian particle-tracking technique was developed to analyze the trajectory and concentration distribution of MPs driven by shear dispersion in river-type lakes. Using the simulation results of MPT-Q3D, which were validated with MP monitoring data and EFDC simulations, we investigated the spatio-temporal variations in MP concentration during both low-flow and flood-flow periods. Simulation results showed that horizontal transport by shear flow contributed more to MP transport than vertical transport, including settling movements based on MP density. Thus, the MP transport during the low-flow period was significantly influenced by the recirculating flow induced by hydropeaking of the NHR, as well as flow blockage caused by the strong inflow momentum from the SHR. During the flood-flow period, flood discharge from the three tributary rivers had an equal influence on MP transport and the variation in MP concentrations around the water intake facilities. Furthermore, the MP residence time was primarily affected by variations in the flow characteristics of the inflowing tributaries rather than the properties of the MP types. Analysis of the influx and efflux of MPs in Paldang Lake revealed that polypropylene was the predominant constituent, accounting for 53.9 % and 75.2 % of all residual MPs during the low-flow and flood-flow periods, respectively.

Multiphysics fields simulation of photothermal catalytic degradation of R134a in a flat plate reactor

Photothermal catalytic degradation is an environment-friendly way to dispose high-global-warming-potential hydrofluorocarbon refrigerants (HFCs). There are challenges in understanding the heat and mass transfer mechanism of this multi-physicochemical process. This study focuses on photothermal catalytic degradation of R134a, one of the hydrofluorocarbon refrigerant, in a flat plate reactor. A numerical model was developed to couple laminar flow, conjugate heat transfer, dilute species transport, surface radiation and chemical reaction. Meanwhile, experiments were conducted to measure the R134a degradation across various temperatures. The parameters of thermal boundary conditions and the kinetics were calibrated by combining the experimental data and the numerical model. The preexponential factor of 0.1146 m/s and activation energy of 21129.1 J/mol were yielded, achieving less than 10 % relative error of the R134a concentration. The average degradation rate was intensified by around one magnitude from 100 °C to 400 °C. Across various temperatures, molecular diffusion always dominated the mass transport process. However, the governing mechanism limiting the photothermal catalytic process was the degradation kinetics, as evidenced by the uniform concentration distribution and the Damköehler number significantly below 1. Several methods were also proposed to enhance the photothermal catalytic degradation rate.

Quantum efficiency enhancement of reflective GaAs photocathodes with exponential-doping structure generating a favorable built-in electric field.

The rapid development of GaAs photocathodes has led to an increased focus on the attainment of high quantum efficiency. Three types of exponential-doping structures with a high to low doping concentration distribution from the interior to the surface are proposed for reflective GaAs emission layers. These three structures generate different built-in electric fields that facilitate photoelectron emission. The one-dimensional continuity equations for the increasing, constant, and decreasing types of built-in electric fields are derived, respectively. The electron concentration distribution and quantum efficiency varying with the wavelength are solved numerically by the finite difference method. The simulation results indicate that the quantum efficiency of the GaAs photocathode with the increasing type of built-in electric field is superior to that with the constant built-in electric field, while the GaAs photocathode with the decreasing type of built-in electric field shows the worst performance. Then, the designed GaAs photocathodes with the increasing and constant types of built-in electric fields are grown by metal-organic chemical vapor deposition and activated by cesium-oxygen alternating deposition. The measured spectral response curves show that the quantum efficiency of the GaAs photocathode with the increasing type of built-in electric field is higher in the whole band than that with the constant type of built-in electric field. In addition, the exponential-doping structure generating the increasing type of built-in electric field is beneficial for improving the surface potential barrier and increasing the surface electron escape probability.

Optimal homotopic strategy for thermal and mass transport in Williamson model flow PDEs under heat generation/absorption and Joule heating

In current paper, we considered the 3-D occurrence of magneto Williamson fluid subjected to linear penetrating expanding sheet. The Williamson liquid is taken into account under the essence of bio convection bordering with Joule heating, heat production. Moreover, Brownian movement combined with thermophoresis diffusion was also analyzed in current study. Central PDEs are modified into system of ODEs on the basis of appropriate similarity transformation utilization. For solution purpose, an optimal approach namely HAM was opted. The critical review based on all involved multifarious constraints across the non- dimensional velocity contour [Formula: see text] energy and concentration distribution. Moreover, across the motile organism distribution was also conducted graphically and depicts total covenant with the former published research work. The drag force effect, Nusselt number, Sherwood number, and motile organism density in tabular form is also proposed in this study. Moreover, Motile organism profile graphically demonstrates decreased demeanor for considered bio convection Lewis number, Peclet number, and also temperature difference constraint whereas results of motile organism density augmented in tabular version for the considered bio convection Lewis number, Peclet number, and also temperature difference constraint.

Incorporating meander to account for the impact of low winds in area source modeling; AERMOD as a case study

ABSTRACT A variety of sources of pollutant emissions can be represented as area sources. These include manure lagoons, landfills, wastewater treatment ponds, and highways. A group of point sources can also be treated as an area source. The impact of an area source is usually computed by representing the area source as a set of line sources perpendicular to the wind direction. As for point sources, the Gaussian horizontal concentration distribution used to compute the contributions of the line sources is likely to overestimate ground-level concentrations when the wind speed is comparable to the standard deviation of the horizontal velocity fluctuations. A variety of methods are used to mitigate this overestimation under these conditions, referred to as meander. As an example of one these approaches, we examine that of AERMOD, EPA’s regulatory model. AERMOD includes meander in modeling the impact of point and volume sources, but has not yet incorporated it into AERMOD’s area source algorithm. This paper describes an approach to include meander in AERMOD’s area source algorithm and demonstrates its impact on concentrations associated with area sources. Implications: Inclusion of wind direction meander in modeling dispersion when the wind speed is low is important in ensuring that AERMOD does not overestimate concentrations under these conditions. In view of the importance of area sources of pollution, the results presented in this paper represent a potential enhancement of AERMOD’s ability to estimate the upper end of the concentration distribution, which forms the basis of the regulatory acceptance of the model.

Dynamic response of flood risk in urban-township complex to future uncertainty

Flooding has emerged as a critical global issue exacerbated by climate change and urban development. This study addresses the significant spatial heterogeneity in flood severity along the urban-rural gradient, which is influenced by variations in ecohydrological and geochemical structures. Despite the importance of understanding the dynamic evolution of flood risk under different disaster scenarios, its influence by urban-rural gradients and response to future uncertainty remain inadequately explored. By developing a comprehensive vulnerability and hazard index framework integrated with a hydrodynamic model, this study not only simulated the dynamic evolution of Urban Vulnerability Value (UV) and Township Hazard Value (TH) during heavy rainfall events but also highlighted their wider implications for flood risk management under future uncertainty. The findings revealed that urban vulnerability exhibited a stable and concentrated distribution, while township hazard values demonstrated significant sensitivity and variability. Notably, the study underscored that under future uncertainty, flood risk responses are likely to intensify (UV and TH increasing by 2.4 and 2.7 times, respectively), with township areas becoming more sensitive to flooding. These insights contributed to a deeper understanding of how urban-rural gradient influences dynamic flood risk, offering valuable guidance for effective flood management strategies in similar regions.

Virus contamination, removal characteristics and quantitative risk assessment from drinking water source to secondary water supply system

The drinking water (DW) supply system is the last line of defense against virus infections for people's DW health. This study systematically evaluated the virus pollution characteristics and human health risks in the entire DW supply systems. The detection frequency range of the virus in DW was 5.30% to 71.21%, and the concentration range at not detected (n.d.) -1.45×105 copies/L. DNA virus like adenovirus was more persistent than RNA viruses like norovirus and enterovirus in the DW system. Drinking water treatment plants (DWTPs) play a crucial role in reducing the target virus with degradation rates ranging from 47.09% to 100% when compared with the removal rates in DW source and secondary water supply (SWS). It was found the persistence and accumulation of the virus in the treated water from DWTPs to the downstream water transmission network. Principal component analysis showed that the virus contamination was positive correlation with water quality indexes like total phosphorus (TP), total nitrogen (TN), dissolved oxygen (DO) but negative correlation with temperature and the dose of free chlorine. Quantitative microbial risk assessment (QMRA) of adenovirus in the SWS showed that the DALYs/person/year of gastroenteritis ranged from 8.11×10-6 to 2.68×10-4 DALYs/person/year. Uncertainty analysis of different distributions of model inputs like virus concentrations showed the risk caused by adenovirus was changed appreciably for different person by using 100,000 Monte Carlo simulations. It is necessary to efficiently remove the virus in the DW systems to ensure human health for the direct ingestion of secondary water supply water.

Spatiotemporal estimation of surface NO2 concentrations in the Pearl River Delta region based on TROPOMI data and machine learning

Nitrogen dioxide (NO2) is a major air pollutant, and its concentration data are crucial for the study of air pollution and its impact on the environment. Although satellite data provide an effective method for estimating surface concentrations on a large scale through integrated modeling, the estimation of surface NO2 concentrations is hampered by the substantial amount of missing satellite data. This restricts in-depth studies of surface NO2 pollution. This study aims to reconstruct the missing data on tropospheric NO2 vertical column density from the TROPOspheric Monitoring Instrument (TROPOMI NO2). Subsequently, the reconstructed TROPOMI NO2 data and other predictor variables were utilized to estimate the daily surface NO2 concentrations at a 1 km resolution for the Pearl River Delta (PRD) region. The TROPOMI NO2 reconstruction models and the surface NO2 estimation model were both developed using the XGBoost algorithm. Additionally, comparative experiments were conducted between the XGBoost model and other traditional machine learning models, and the performances of the XGBoost model were evaluated through 10-fold cross-validation (CV) sample-based and site-based evaluations. The results indicate that the sample-based and site-based CV R2 values were 0.873 and 0.709, respectively. The feature importance scores indicate that TROPOMI NO2 was the most significant variable contributing to the estimation model. This indicates that the reconstruction of TROPOMI NO2 data and the development of an Extreme Gradient Boosting (XGBoost) model are suitable for the spatiotemporal estimation of surface NO2 concentrations in the PRD region, effectively reflecting the spatiotemporal distribution and evolution of surface NO2 concentrations in the area.

Modeling of non-equilibrium suspended sediment transport process in open channel flows with vegetation

A mathematical model based on advection-diffusion theory is established to study the non-equilibrium sediment transport process in vegetated channels. The effects of vegetation on velocity distribution and sediment diffusion coefficients were considered, respectively. Validation against experimental data from flume studies confirms the model's ability to accurately predict the longitudinal sediment deposition rate and the vertical distribution of suspended sediment concentration (SSC). A comparative analysis of three sediment diffusion coefficient formulations indicates that the linear-exponential formula provides a more precise estimate of εsz, and the linear-exponential formula performs well in predicting the turbulent diffusion coefficients of both rigid and flexible vegetation when gently swaying. Moreover, the distance required for SSC to regain equilibrium is influenced by the submergence level of the vegetation canopy. At lower submergence levels, the canopy shear vortices significantly affect the vertical exchange of sediment, and the sediment diffusion coefficients exhibit pronounced stratification near the vegetation canopy. An increase in vegetation density at these lower submergence levels intensifies the shear vortices, thereby extending the distance needed for SSC to reach equilibrium. At higher submergence levels, the impact of canopy shear vortices is lessened, which reduces sediment diffusion coefficient stratification characteristics, and the flow is similar to rough boundary layer flow. An increase in vegetation density increases flow resistance, which shortens the distance required for SSC to attain equilibrium. However, further efforts are required to explore turbulent characteristics with highly flexible vegetation motion and the grain size distribution of non-uniform sediments in vegetated flows.

Lung cancer mortality attributable to residential radon in Germany

The radioactive gas radon is one of the most important risk factors for lung cancer after smoking. This article aims to estimate the annual number of lung cancer deaths attributable to residential radon exposure in Germany and its federal states using updated data and an advanced calculation method. Data on lung cancer mortality (2018–2022), smoking behavior (2017), and on the estimated distribution of radon concentration based on a radon residential study (2019–2021) in Germany are used. The risk model employed is derived from the pooled European residential radon study, indicating that excess relative risk for lung cancer increases by 16% per 100 becquerels per cubic meter (Bq/m3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}$$\\end{document}) of corrected long-term radon concentration. It is estimated that a total of around 2800 lung cancer deaths per year (95% confidence interval (CI) 900–5100) are attributable to residential radon in Germany. This represents a population attributable fraction of 6.3% (95% CI 2.1–11.4%). Notably, radon-attributable lung cancer deaths occur not only among current (41%) but also significantly among former smokers (41%) and those who have never smoked (19%). The results confirm that radon in homes is an important risk factor for lung cancer, highlighting the need for protective measures against radon for all population groups in Germany.

Electron transport in quasi-ballistic FETs subjected to a magnetic field

We report the study of quasi-ballistic electron transport in short FETs subjected to magnetic field. Spatial distributions of electron concentrations, velocities, Hall currents, and voltages in the short FET channels are determined. The basic properties of current–voltage characteristics of quasi-ballistic FETs in magnetic field are analyzed, among them the kink-like characteristics of the near-ballistic device. Peculiarities of magnetoresistance of such FETs are studied for low and high magnetic fields and different current regimes. For nonlinear current regimes, we revealed significantly larger magnetoresistance for the devices with higher ballisticity. Numerical estimates of studied effects are presented. We suggest that the found results contribute to the physics of short FETs and can be used for developing nanoscale devices for particular applications.

Estimation of the proportion of cardiovascular disease cases in France attributable to high concentrations of low-density lipoprotein cholesterol

BackgroundElevated concentrations of low-density lipoprotein cholesterol (LDL-C) are highly prevalent and are associated with the development of cardiovascular diseases. AimTo estimate the proportion of cardiovascular disease cases attributable to high concentrations of LDL-C (population attributable fraction [PAF]) in France in 2017, based on the most recent individual data on LDL-C, and the attributable burden on hospitalizations and death. MethodsWe estimated the PAF of high LDL-C concentrations for ischaemic heart disease (IHD), ischaemic stroke and aortic valve stenosis (AVS). Distributions of LDL-C concentrations were obtained from the most recent French health examination representative survey (ESTEBAN). The relative risks of each disease per 1-mmol/L increase in blood LDL-C were obtained either from the most appropriate meta-analyses or from Mendelian randomization. ResultsThe PAF of high LDL-C concentrations varied between 44.2% (95% CI 24.6%–60.5%) for IHD-related death and 49.4% (95% CI 35.6–60.8%) for IHD-related years-of-life lost (YLL), 22.5% (95% CI 0.0–43.3%) and 25.5% (95% CI 11.6–36.8%) for ischaemic stroke indicators, and 29.0% (95% CI 8.6–45.4%) and 29.3% (95% CI 8.4–45.6%) for AVS indicators. Overall, 230,000 hospitalizations, 1,303,000 prevalent cases and 23,000 deaths were estimated to be attributable to high LDL-C concentrations, with most cases related to IHD. PAFs were similar across sex and cardiovascular diseases, whereas PAF strongly varied with age for IHD and ischaemic stroke, with PAF reaching 80.6% (95% CI 55.3–92.7%) and 60.9% (95% CI 33.8–80.8%), respectively, in the group aged 35–44 years. ConclusionThe high estimated PAF of elevated LDL-C concentrations for IHD, ischaemic stroke and AVS support the urgent need to reduce the prevalence of hypercholesterolaemia in this French population.

The influence of pulsation ventilation on the removal and distribution of gas accumulation areas during gas leakage in industrial plants

A ventilation system with a constant velocity air supply might form airflow stagnant zones in industrial plants, making it challenging to dilute hazardous gas effectively. In this study, a novel ventilation mode called pulsating ventilation, which can potentially dilute the hazardous gas better, was applied in a ventilated room with nozzle air supply. Three different scenarios of gas accumulation were assumed, with the location of gas accumulation situated at the rear, near the floor, and in the corners of the room. Both the distribution of CO2 concentration and the efficiency of reducing the indoor CO2 concentration to the safety threshold were analyzed to evaluate the ventilation performance of pulsating ventilation. The results showed that pulsating ventilation outperformed constant velocity air supply in expeditiously eradicating gas accumulation areas for equivalent total air volumes. When the gas accumulation areas were located at the rear of the room, close to the floor, and in the corner of the room, pulsation ventilation reduced the time for the indoor CO2 concentration to drop to the safety threshold by 36.19%, 27.23%, and 36.25%, respectively. Holding the period constant, an increased amplitude correlated with a swifter decrease in peak pollutant concentration. Except for the case where the gas accumulation areas are close to the floor, when the amplitude is constant, the larger the period, the faster the peak concentration in the gas accumulation areas decreases.

WITHDRAWN: The enhanced heat transfer and flow dynamics of tangent hyperbolic and Newtonian nanofluids under inclined variable magnetic field

This paper aims to analyze the thermal conductivity of tangent hyperbolic non-Newtonian fluids and Newtonian nanofluids over a porous, inclined, stretching sheet with motile microorganisms. It also examines the impact of inclined variable magnetic field, activation energy, thermal radiation, thermophoresis and Brownian motion. The novelty of this research lies in the simultaneous use of inclined geometry and an inclined variable magnetic field. The findings optimize environmental and food processing applications, drug delivery, thermal management, lubrication, and enhanced oil recovery. A far-reaching analysis compares the behaviors of tangent hyperbolic fluid with Newtonian fluid. Appropriate similarity functions are used to convert the governing system of nonlinear PDEs for tangent hyperbolic fluid to dimensionless ODE. MATLAB’s boundary value solver BVP4C is then used to solve these ODEs numerically. This study explores various characteristics, including temperature, velocity, concentration, and microorganism distribution. In the essence of this computational study, the impacts of inclined angle, porosity, mixed convection, Hartmann number and Weissenberg number on the velocity of the fluid are analyzed. The main findings are that higher Prandtl numbers reduce heat transfer rates, while thermophoresis and Brownian motion enhance heat flow. Lewis and Peclet numbers show declining tendencies in motile microorganisms, with magnetic fields influencing their distribution within the fluid; this is useful in biotechnology and environmental applications. Consequently, the effect is greater in the case of non-Newtonian fluids which depend more on the inclination angle, inclined variable magnetic field strength, thermal conductivity and activation energy when compared with the Newtonian fluids.