Size Parameters Research Articles

Rapid Detection of Microplastics/Nanoplastics Directly Exposed to Blood During Intravenous Injections via Mie Scattering Spectra

Microplastics/nanoplastics (M/NPs) are pervasive in the environment, leading to inevitable human exposure through various pathways and raising significant public and scientific concern. Understanding the sources and levels of M/NPs in human blood is crucial for environmental health studies. This work examined the content, type, shape, and size of M/NPs released directly into the bloodstream from medical devices via saline solution during intravenous (IV) injection. The results of the Mie scattering spectra method show that the M/NPs content from infusion bags was 1.0 ± 0.7μg/L, mainly fibers, polyethylene, and polypropylene, with fragments being predominant. During a IV process, the initial 12mL of saline from infusion tubes contained 8.4 ± 3.6μg/L of M/NPs, primarily polyvinyl chloride and fibers. These results suggest that M/NPs exposure during IV therapy mainly originates from infusion tubing, necessitating high concern for exposure risks. Recommendations include: 1) reducing non-essential IV treatments, 2) discarding the initial 12mL of saline solution flowing through the tubing during essential IV therapy, and 3) expediting the development of legal requirements and detection standards by national authorities and the healthcare industry to mitigate the risk of M/NPs exposure in the bloodstream.

Bayesian statistical analysis reveals spatial heterogeneity in Cyclone Thane deposits from Southeast India

Modern and geological records of storm sedimentary deposits preserved on siliciclastic coastlines are important archives to evaluate the past and current magnitude and impacts of.storms. Examination of modern storm deposits also offers the opportunity to evaluate the similarities and differences between storm and other coastal overwash processes and hazards.We examined the stratigraphy and sedimentary characteristics of the 31st December 2012 Cyclone Thane and underlying coastal units from 14 pits from six sites from the coastal zone of Tamil Nadu Province, southeast India. We analysed the grain size parameters, grain shape, and heavy mineral proportions of each deposit in high resolution and examined the sedimentary structures of each unit. For the first time, we use Bayesian factors to quantitatively evaluate the similarities and differences between the storm sedimentary deposits and other co-located coastal sedimentary deposits. At several sites, the storm deposits differ in several parameters from the underlying coastal deposits, but at some locations, distinguishing between different depositional units cannot be achieved. In comparing the storm deposits from the different sites, mean grain size results in the most coherent pattern with closely located sites having similar mean grain size, and more southerly sites being finer grained. The other measured parameters show a far less coherent pattern with adjacent sites often preserving larger differences than more distal sites attesting to very local hydrodynamic variations during sediment deposition. As with the sedimentary parameters, the sedimentary structures formed during sediment deposition preserved at each site are highly variable. To date, the presence of terminal foresets at the landward edge of washover fans remains the only diagnostic feature of storm deposition, but that this feature is not ubiquitous across all storm deposits. Our findings demonstrate the spatially heterogeneous nature of storm sediment deposition and the challenges of identifying storm deposits in coastal siliciclastic sequences. The use of Bayesian statistical approaches also offers a robust method for evaluating and discriminating between coastal sediment deposits that has many advantages over traditional frequentist approaches. This method can easily be applied to other sedimentary depositional environments.

Tuneability and optimum functionality of plasmonic transparent conducting oxide-Ag core-shell nanostructures

Tunning localized surface plasmon resonance (LSPR) in transparent conducting oxides (TCO) has a great impact on various LSPR-based technologies. In addition to the commonly reported mechanisms used for tunning LSPR in TCOs (e.g., size, shape, carrier density modifications via intrinsic and extrinsic doping), integrating them in core-shell structures provides an additional degree of freedom to expand its tunability, enhance its functionality, and widen its versatility through application-oriented core-shell geometrical optimization. In this work, we explore the tuneability and functionality of two TCO nanostructures; indium doped tin oxide (ITO) and gallium doped zinc oxide (GZO) encapsulated with silver shell within the extended theoretical Mie theory formalism. The effect of core and shell sizes on LSPR peak position and line width as well as absorption and scattering coefficients is numerically investigated. Simulations showed that LSPRs of ITO-Ag and GZO-Ag core-shell nanostructures have great tunning capabilities, spanning from VIS to IR spectral range including therapeutic window of human tissue and essential solar energy spectrum. Potential functionality as refractive index sensor (RIS) and solar energy absorber (SEA) are examined using appropriate figure of merits (FoM). Simulations indicate that a geometrically optimized core-shell architecture with exceptional FoMs for RIS and SEA can be realized. Contrary to carrier density manipulation, integrating TCO cores to metallic shells proves to be an effective approach to enhance tunability and optimize functionality for high performance TCO-based plasmonic devices, with minimum impact on the inherited physical and chemical properties of the used TCO-core materials.

Multi-particle Size Measurement Using Mie Scattering via Elliptically Arranged Mirror Array

Multi-particle Size Measurement Using Mie Scattering via Elliptically Arranged Mirror Array

Morphological variability and vitality of Rindera tetraspis (Boraginaceae) in the South Urals and Western Kazakhstan

Population studies of Rindera tetraspis Pall., a rare endemic species of the steppe zone of the European part of Russia and Kazakhstan, were carried out. The study of the habitats of 11 populations in the Orenburg Region and the Republic of Kazakhstan has shown that the species is confined to various variants of calciphyte steppes on chalk substrates or sandstones. In terms of most morphometric indicators, the northern coenopopulation “Rodnichny” is the leader; the minimum values are noted in the coenopopulation “Verkhnechebendinskie Chalk Mountains, northern extremity”. The discriminant analysis has revealed morphostructural differences between individuals from the majority of coenopopulations. In terms of vitality, four coenopopulations are prosperous, seven ones are depressed. The optimal conditions for the species growth are in the northern part of its range, in more favorable climatic conditions in terms of temperature and humidity, mainly on soils of sand origin. When moving southward, a decrease in size parameters of individuals is observed, associated with insufficient moisture, while their morphological diversity increases. The state of R. tetraspis coenopopulations is stable, but the species is not provided with proper protection measures, so further monitoring of its habitats and improvement of conservation measures are necessary.

Forensic-geology-based magnetic analysis of beach sediments from the Shimokita Peninsula, Japan.

The occurrences of various illegal activities on beaches require effective geological and environmental investigation methods. Among these methods, the room-temperature magnetic analysis of soils and sediments represents a nondestructive investigation method for various amounts, types, and grain sizes of magnetic minerals. Here, to verify the usefulness of magnetic analysis in forensic geology research, beach sediment samples from nine sites in the Shimokita Peninsula, Japan, were measured using magnetic analysis to determine the correlations between their concentration-dependent magnetic parameters and actual regional characteristics. The results revealed that the values of various parameters, namely the low-field magnetic susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization (IRM), were relatively higher at sites near Ti and Fe sedimentary ore deposits. Further, thermomagnetometry results revealed that magnetite was the main magnetic carrier of the sediments. Moreover, pyrrhotite was detected around Ti-Fe mine sites. Furthermore, the results of the investigated parameters reflected the regional characteristics of the amount of magnetic minerals in the beach sediments. Low-temperature IRM curves and the magnetic grain size parameter also displayed sample-site-reflective characteristics. Thus, we believe that magnetic analysis represents an effective method for estimating the provenance of beach sediments in forensic geology research.

A Thermal Impedance Model for IGBT Modules Considering the Nonlinear Thermal Characteristics of Chips and Ceramic Materials

The traditional method of calculating junction temperature does not consider the dependence of a material’s thermal conductivity on temperature, in which the thermal conductivity changes with temperature. However, with an increase in junction temperature, the temperature sensitivity (TS) will have a more significant impact on the actual temperature of chips. This study established an improved IGBT equivalent thermal impedance model that considers the nonlinear characteristics of the TS of chips and ceramic materials. The Fourier series analysis method was used to obtain the heat flux density curve, and then the heat diffusion angles of each layer were solved. Moreover, iterations were performed until the thermal conductivity and temperature of the chip and ceramic layers matched the nonlinear characteristics of the TS. When the power loss was less than 200 W, the maximum error of the junction temperature calculated by the proposed method considering TS was 3%, while the maximum error of the method without considering TS was 9.5%. Compared with the finite element simulation, the proposed method has a faster solving speed and high accuracy. The proposed method only requires the input material parameters, size parameters, and boundary conditions to solve the junction temperature, which has strong practicality and high accuracy.

Generating X-Ray Transit Profiles with Batman

We present an adaptation of the exoplanet transit model code batman, in order to permit the generation of X-ray transits. Our underlying extended coronal model assumes an isothermal plasma that is radially symmetric. While this ignores the effect of bright, active regions, observations of transits in X-rays will require averaging across multiple epochs of data for the foreseeable future, significantly reducing the importance of more complex modeling. Our publicly available code successfully generates the predicted W-shaped transit profile in X-rays due to the optically thin nature of the emission, which concentrates the expected observational emission around the limb of the photospheric stellar disk. We provide some examples based on the best known X-ray transit target, HD 189733 b, and examine the effect of varying the planet size, coronal temperature, and impact parameter on the resulting transit profile. We also derived scaling relationships for how the overall transit detectability is affected by changing these parameters. Over most of the parameter space, we find that the detectability scales linearly with the cross-sectional area of the planet in X-rays. The relationship with increasing coronal temperature is less fixed, but averages out to a power law with slope −1/4 except when the impact parameter is high. Indeed, varying impact parameter has little effect on detectability at all until it approaches unity.

OGC SO36 - Complications of palliative oesophageal cancer stent insertion: Audit for a five year period

Abstract Background Oesophageal stents are commonly used for the palliative treatment of inoperable oesophageal malignancy[1]. Stenting of the oesophagus may provide safe and quickly effective management for late-stage disease symptoms. However, there are common complications associated with the oesophageal stents. This audit looks at the types of early and delayed complications from oesophageal stenting, specifically for malignancy. We aim to stratify the types of complication, association between complications and the type of stent used, and the frequency of repeat stenting or repositioning. This will provide patients with better expectations of the complications and compare our practice against published international standards Method All fluoroscopy guided stent insertions between 1/1/2019 and 31/12/2023 for oesophageal malignancy were requested from the hospital radiology department. 101 patients were included for analysis. Their basic demographics were obtained, as well as a disease profile including tumour histology, staging and whether they underwent radiotherapy or chemotherapy. Complications of the stent insertion were then logged. The number of times stents were replaced or repositioned were noted. The type of stent, size parameters, features such as covering, antimigration device and anti-reflux valve were also assessed. In addition, any hospital admissions related to stent complications were also recorded. Results Of 101 patients, the median age was 75, with a higher proportion of male patients ( 71%). After stent fitting there was a median survival length of 94 days. 45% of patients had complications related to the stent. Stent migration was the most frequent complication, 14% of patients experienced stent migration into the stomach, which required repositioning or restenting. Both middle and lower oesophagus stents had equal complication rate. 25% of patients were reported to have overgrowth of tumour affecting the stent, and there was no significant difference in those fitted with a covered stent, meant to reduce overgrowth complications. Conclusion The complications directly resulting from oesophageal stents may adversely affect the palliation of oesophageal cancer patients. In this cohort, the most commonly occurring complications were migration of the stent, immediate symptoms after insertion, and overgrowth of the tumour. Although overgrowth of tumour is part of the disease progression, in many cases it made retrieval of the existing stent or reinsertion more difficult. Our results found no significant difference for complication rates between the different stents, nor the inclusion of antimigration devices. There were no deaths directly due to the stent and no oesophageal perforations reported.

Application of functional magnetic resonance imaging to evaluate renal structure and function in type 2 cardiorenal syndrome.

There is a lack of diagnostic non-invasive imaging technology for assessing the early structural and functional changes of the kidney in type 2 cardiorenal (CRS) patients. This study aims to explore the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) for clinical application in type 2 CRS patients, to provide imaging markers for the assessment of kidney damage. This is a retrospective observational clinical study conducted in Nanjing, China. The clinical characteristics, including age, gender, medical history, laboratory results, and ultrasound and magnetic resonance imaging results were collected from the electronic medical record. Thirty-one patients with type 2 CRS, 20 patients with chronic heart failure (HF) and 20 healthy controls were enrolled and divided into type 2 CRS, HF and control groups. All the participants underwent magnetic resonance imaging (MRI) scanning. The apparent diffusion coefficient (ADC) value and IVIM-DWI parameters including true diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) were obtained. The correlation between estimated glomerular filtration rate (eGFR), renal size and imaging parameters was evaluated by Spearman correlation analysis. ADC and D of the renal cortex in patients with type 2 CRS were lower than those in the healthy control group. ADC and f in the HF group were lower than those in the control group. D was positively correlated with the length (r = 0.3752, P = 0.0013) and transverse diameter (r = 0.3258, P = 0.0056) of the kidney. ADC (r = 0.2964, P = 0.0121) and D (r = 0.3051, P = 0.0097) were positively correlated with eGFR. Renal cortical ADC and D values could distinguish type 2 CRS patients from the healthy controls with area under the curve (AUC) of 0.723 and 0.706, respectively. The ADC and D values were not only correlated with renal function, but also had lower levels in type 2 CRS. The IVIM-DWI parameter D was also related to kidney size, but further research is needed to determine whether it can be used as a novel imaging marker for type 2 CRS.

Multi-objective optimization design method for the dimensions and control parameters of curling hexapod robot based on application performance

The curling hexapod robot is different from previous curling robots, which can mimic the throwing actions of curlers. To ensure its performance, the size and control parameters of the robot need to be optimized. However, there is still a lack of parameter design optimization methods for hexapod curling robots based on application performance and considering the coupling effects of size and control parameters. To meet this demand, this paper combines Simscape Multibody simulation modeling and genetic algorithm to propose a multi-objective optimization method for the dimensions and control parameters of curling hexapod robot based on application performance. This method uses Simscape Multibody to establish a parametric model of the curling robot, and proposes an optimization search method using genetic algorithms based on constraints and objective functions. Finally, the dimensions and control parameters of the curling robot that meet the application performance requirements are solved through the optimization method.

Exploring How the Surface-Area-to-Volume Ratio Influences the Partitioning of Surfactants to the Air-Water Interface in Levitated Microdroplets.

Quantitative characterization of the surface of microdroplets is important to understanding and predicting numerous chemical and physical processes, such as cloud droplet formation and accelerated chemistry in microdroplets. However, it is increasingly appreciated that the surface compositions of microdroplets do not necessarily match those of macroscale solution due to their large surface-area-to-volume (SA-V) ratios and confined volumes. In this work, we explore how both droplet size and composition affect the surface composition of microdroplets by measuring the equilibrium surface tensions of levitated microdroplets containing a single surfactant. We measure the critical micelle concentrations (CMCs) for surfactants of various strengths (macroscale CMC values ranging from 0.02 to 10 mM) in microdroplets with radii ranging from 5 to 25 μm. We accurately model the surface tensions of microdroplets using an equilibrium partitioning model that only requires droplet size and adsorption parameters from macroscale measurements as inputs. Our model predicts that surfactants have an "effective CMC" in microdroplets that is always larger in value than the corresponding macroscale CMC. In some instances, the effective CMC of a surfactant in microdroplets is several orders of magnitude larger than both its macroscale CMC and its macroscale solubility limit. We present a simple expression for the effective CMC in microdroplets that depends on both the macroscale CMC of a surfactant and the SA-V ratio of the microdroplet. Ultimately, our experimental results and model can be used broadly to predict microdroplet surface compositions when investigating surface-driven accelerated chemistry in microdroplets or estimating cloud droplet activation.

The Optical Forces and Torques Exerted by Airy Light-Sheet on Magnetic Particles Utilized for Targeted Drug Delivery

The remarkable properties of magnetic nanostructures have sparked considerable interest within the biomedical domain, owing to their potential for diverse applications. In targeted drug delivery systems, therapeutic molecules can be loaded onto magnetic nanocarriers and precisely guided and released within the body with the assistance of an externally applied magnetic field. However, conventional external magnetic fields generated by permanent magnets or electromagnets are limited by finite magnetic field gradients, shallow penetration depths, and low precision. The novel structured light field known as the Airy light-sheet possesses unique characteristics such as non-diffraction, self-healing, and self-acceleration, which can potentially overcome the limitations of traditional magnetic fields to some extent. While existing studies have primarily focused on the manipulation of dielectric particles by Airy light-sheet, comprehensive analyses exploring the intricate interplay between Airy light-sheet and magnetic nanostructures are currently lacking in the literature, with only preliminary theoretical discussions available. This study systematically explores the mechanical response of magnetic spherical particles under the influence of Airy light-sheet, including radiation forces and spin torques. Furthermore, we provide an in-depth analysis of the effects of particle size, permittivity, permeability, and incident light-sheet parameters on the mechanical effects. Our research findings not only offer new theoretical guidance and practical references for the application of magnetic nanoparticles in biomedicine but also provide valuable insights for the manipulation of other types of micro/nanoparticles using structured light fields.

Vision-guided crack identification and size quantification framework for dam underwater concrete structures

Remotely operated vehicles with cameras provide a non-contact inspection solution for dam underwater structural defect detection. However, manual information extraction methods suffer from problems like labor costs and high misjudgment. This study proposes an integrated dam underwater crack identification and size quantification framework using machine vision and deep learning. First, a real-time automatic detection framework for dam underwater cracks is built via You Only Look Once v5 (YOLOv5), and four different backbone detectors are introduced to balance detection accuracy and speed. Then, the Swin-Transformer module is inserted into the YOLOv5 model to enhance its feature extraction capability and small object detection capability. Next, a method for measuring the true size of cracks was constructed based on deep learning and infrared laser rangefinders. In this study, physical model experiments and actual engineering projects are combined to validate the generalization capability of the proposed crack identification and size quantification method. Experimental results show that the Swin-Transformer-based YOLOv5 model effectively balances detection accuracy and speed with a precision of 0.986, a recall of 0.979, a mean average precision of 0.985, and a frame rate of 68 frames per second in detecting underwater crack images with 768 × 576 pixels. In addition, the proposed method can accurately identify and detect cracks in complex underwater scenes, including obstacle interference, tilt shooting angle, uneven illumination, and turbid water scenarios. Moreover, the method proposed in this paper can quantify the overall size and geometric parameters of underwater cracks with relatively small errors.

Estimation of thermal emission from mixture of CO2 and H2O gases and fly-ash particles

Abstract In the present work the thermal emission from gases and particle mixture is studied comprehensively. The mixture consist of CO2 and H2Ogases along with fly-ash particles and their spectral radiative properties are obtained from HITEMP database and Mie theory, respectively. The Line-by-line method, known for high accuracy is used to estimate radiative heat transfer from gases and particle mixture. Three distinct cases, i.e, pure absorption/emission, pure scattering, and their combined effects are investigated. The spectral radiative transfer equation is solved by finite angle method (FAM) and the correctness of the results is ensured by principle of energy conservation. The anisotropic scattering is modeled using the Henyey-Greenstein method. The influence of radiative properties of the participating medium, along with wall and cavity temperatures, on heat transfer and emission spectrum is evaluated. The radiative heat transfer enhances with introduction of the particles in the gaseous mixture. For pure scattering medium, the emission spectrum on each wall differs and also varies from the emission spectrum of the emitting wall. The particle influence grows notably with higher volume fractions in gaseous mixture. While there is a notable contribution of anisotropic scattering in a purely scattering medium, its significance diminishes in an absorbing, emitting, and scattering medium.

Silica gels doped with gold nanoparticles and gold thiolate complexes: The effect of heating and preparation conditions

A novel sol-gel strategy for the preparation of silica nanocomposites, containing gold nanoparticles (AuNPs), Au(I)-thiolate complexes (Au-SC12) or both disperse phases is demonstrated. The color of the species depends on the size and surrounding of the AuNPs. The nanocomposites obtained are characterized with UV/Vis reflectance spectroscopy, X-Ray diffraction, TEM / EDAX and thermal conductivity measurements. An analysis of the UV/VIS spectra, based on Mie's theory, suggests the presence of 5 - 30 nm AuNPs with different chemical surroundings. Heating of the nanocomposites at 700 °C leads to red or violet colored SiO2:AuNPs powders. The thermal conductivity of the nanocomposites is about 0.05–0.07 W/m.K, depending on sintering and chemical composition. A discussion about the microstructure of the composites is also presented.

Retrieval of refractive index and water content for the coating materials of aged black carbon aerosol based on optical properties: a theoretical analysis

Abstract. Water content in the coatings of aged black carbon (BC) aerosol can be reflected through the complex refractive index. In this study, the retrieval of the refractive index and water content for non-absorbing coatings of BC aerosol during hygroscopic growth (RH = 0 %–95 %) based on scattering and absorption properties is theoretically investigated. Optical properties of morphologically realistic fractal BC aerosols are simulated using the multiple-sphere T-matrix method (MSTM), the optical equivalent refractive index of coating material is retrieved based on the Mie theory, and the water content in coatings is further retrieved using effective medium theory. Results show that the scattering property performs best in retrieving the refractive index and water content. The retrieval errors of the refractive index of heavily aged BC aerosols are less than 10 % at high relative humidities (RHs), while partially coated BC and thinly coated BC have larger errors. The regularity of retrieved water content is similar to that of the refractive index retrieved, and the retrieved water content errors range from 2 % to 63 % for heavily coated BC. This study provides a helpful optical method to obtain the water content of BC coatings.

Leveraging machine learning to streamline the development of liposomal drug delivery systems

Drug delivery systems efficiently and safely administer therapeutic agents to specific body sites. Liposomes, spherical vesicles made of phospholipid bilayers, have become a powerful tool in this field, especially with the rise of microfluidic manufacturing during the COVID-19 pandemic. Despite its efficiency, microfluidic liposomal production poses challenges, often requiring laborious, optimization on a case-by-case basis. This is due to a lack of comprehensive understanding and robust methodologies, compounded by limited data on microfluidic production with varying lipids. Artificial intelligence offers promise in predicting lipid behaviour during microfluidic production, with the still unexploited potential of streamlining development. Herein we employ machine learning to predict critical quality attributes and process parameters for microfluidic-based liposome production. Validated models predict liposome formation, size, and production parameters, significantly advancing our understanding of lipid behaviour. Extensive model analysis enhanced interpretability and investigated underlying mechanisms, supporting the transition to microfluidic production. Unlocking the potential of machine learning in drug development can accelerate pharmaceutical innovation, making drug delivery systems more adaptable and accessible.

Intra-Aneurysmal High-Resolution 4D MR Flow Imaging for Hemodynamic Imaging Markers in Intracranial Aneurysm Instability.

Prediction of aneurysm instability is crucial to guide treatment decisions and to select appropriate patients with unruptured intracranial aneurysms (IAs) for preventive treatment. High-resolution 4D MR flow imaging and 3D quantification of aneurysm morphology could offer insights and new imaging markers for aneurysm instability. In this cross-sectional study, we aim to identify 4D MR flow imaging markers for aneurysm instability by relating hemodynamics in the aneurysm sac to 3D morphologic proxy parameters for aneurysm instability. In 35 patients with 37 unruptured IAs, a 3T MRA and a 7T 4D MRI flow scan were performed. Five hemodynamic parameters-peak-systolic wall shear stress (WSSMAX) and time-averaged wall shear stress (WSSMEAN), oscillatory shear index (OSI), mean velocity, and velocity pulsatility index-were correlated to 6 3D morphology proxy parameters of aneurysm instability-major axis length, volume, surface area (all 3 size parameters), flatness, shape index, and curvedness-by Pearson correlation with 95% CI. Scatterplots of hemodynamic parameters that correlated with IA size (major axis length) were created. WSSMAX and WSSMEAN correlated negatively with all 3 size parameters (strongest for WSSMEAN with volume (r = -0.70, 95% CI -0.83 to -0.49) and OSI positively (strongest with major axis length [r = 0.87, 95% CI 0.76-0.93]). WSSMAX and WSSMEAN correlated positively with shape index (r = 0.61, 95% CI 0.36-0.78 and r = 0.49, 95% CI 0.20-0.70, respectively) and OSI negatively (r = -0.82, 95% CI -0.9 to -0.68). WSSMEAN and mean velocity correlated negatively with flatness (r = -0.35, 95% CI -0.61 to -0.029 and r = -0.33, 95% CI -0.59 to 0.007, respectively) and OSI positively (r = 0.54, 95% CI 0.26-0.74). Velocity pulsatility index did not show any statistically relevant correlation. Out of the 5 included hemodynamic parameters, WSSMAX, WSSMEAN, and OSI showed the strongest correlation with morphologic 3D proxy parameters of aneurysm instability. Future studies should assess these promising new imaging marker parameters for predicting aneurysm instability in longitudinal cohorts of patients with IA.

Numerical analysis of axially loaded concrete-filled steel tubular columns strengthened with CFRP grid-reinforced ECC

Carbon fiber-reinforced polymer (CFRP) and engineered cementitious composites (ECC) are commonly used to reinforce structural elements, with proven effectiveness in enhancing the performance of concrete-filled steel tube (CFST) columns as shown in prior experimental studies. However, the complex interaction among the components of the reinforced columns, including CFRP, ECC, the steel tube, and the concrete core, as well as the underlying mechanical mechanisms, remain insufficiently understood. This research aims to fill these gaps by developing a 3D finite element (FE) model of circular CFST short columns reinforced with CFRP grid-reinforced ECC for comprehensive numerical analysis. Sensitivity analyses are conducted to determine the governing parameters in the numerical simulation, including mesh size and critical plasticity parameters for the concrete damage model, such as the ratio of the second stress invariant on the tensile meridian to that on the compressive meridian (Kc), and the dilation angle (ψ) for both the concrete core and ECC. The model also accounts for the effects of concrete confinement provided by the CFRP grid-reinforced ECC layer and the circular steel tube. The accuracy of the FE model is validated against existing experimental data, and the model is subsequently used to investigate the behavior of reinforced CFST columns under varying geometric and material properties. The study examines failure modes, axial load-displacement responses, stress distributions, and the contribution of each material component to the load-bearing capacity of the strengthened columns. The results indicate an increase in ultimate axial strength ranging from 13% to 20% for the reinforced CFST columns. While the compressive strength of the ECC has a moderate effect on axial resistance, increasing ECC thickness, concrete strength, and steel tube yield strength significantly enhances the columns’ load-bearing capacity. Finally, a novel design model is proposed and validated, which accounts for the confinement effects provided by the CFRP grid and ECC on the concrete core.