Quadratic Fitting Research Articles

Comparison of tibial and femoral physeal diffusion tensor imaging in adolescents.

Distal femoral diffusion tensor imaging (DTI) is a predictor of height gain but it is uncertain whether DTI can demonstrate differences in growth potential between the tibia and femur. To explore the differences in structure and growth potential of the proximal tibia physeal-metaphyseal complex compared to those of the distal femur through DTI tractographic characterization and DTI metric comparison. Prospective cross-sectional study involved 108 healthy children (59 females) aged 8-14years (females) and 10-16years (males) around the growth spurt. We acquired knee DTI once at 3T with b-values of 0s/mm2 and 600s/mm2. Tract parameters including number, length, volume, and fractional anisotropy were measured. Regression analysis with linear and negative binomial models, incorporating bone age-based quadratic fitting, characterized DTI parameter changes in relation to bone age and sex, as well as variations between physes. Femorotibial ratios were calculated based on paired DTI parameter absolute values during peak height gain. The study was approved by the institutional review board of two tertiary pediatric centers in compliance with the Health Insurance Portability and Accountability Act. Proximal tibial tracts were more numerous in the central physis, whereas distal femoral tracts predominated peripherally. Tract volume rose and fell during adolescence and peaked earlier in females (140-160months vs. 160-180months, P=0.02). At maximal height velocity (160months), tibial tract volume (5.43cc) was 37.4% of total knee tract volume (14.53cc). Tibial fractional anisotropy decreased and then increased, both earlier than the femur. Proximal tibial and distal femoral tract distributions differ. The tibia accounts for 37.4% of total knee tract volume during maximal height velocity. Tract volumes rise and fall, earlier in females. Tibiofemoral ratios of DTI metrics resemble known ratios of growth rates between tibia and femur.

Optimized evaluation of ground motion intensity measures for the prefabricated cantilevered roadbed structure in mountainous areas

The prefabricated cantilevered roadbed structure (PCRS) is a novel design that addresses the significant excavation and embankment volume associated with traditional mountainous roadbeds. The seismic performance of it has not yet been fully investigated. Seismic fragility analysis is one of the main methods for assessing the damage pattern of a structure, and the ground motion intensity measure (IM) is a key parameter affecting the damage assessment results. To this end, a finite element model is first conducted based on structural load-bearing capacity verification experiments, relying on a prefabricated cantilevered roadbed structure in a mountainous region. Then, the nonlinear time-history analysis of the structure was carried out, and 20 common IMs were selected and compared from the perspectives of practicality, efficiency, proficiency, and sufficiency. Finally, the seismic fragility analysis of the structure is conducted based on the optimal IM. The analysis results indicate that the peak ground acceleration of response spectrum (PSA) is the optimal IM for such structures. Quadratic fitting exhibits higher accuracy compared to linear fitting. Among all components, fixed-end foundations are identified as the most vulnerable. Anchored reinforcement remains elastic throughout the seismic response calculations and suffers little damage.

Impact of contraction intensity and ankle joint angle on calf muscle fascicle length and pennation angle during isometric and dynamic contractions

During muscle contraction, not only are the fascicles shortening but also the pennation angle changes, which leads to a faster contraction of the muscle than of its fascicles. This phenomenon is called muscle gearing, and it has a direct influence on the force output of the muscle. There are few studies showing pennation angle changes during isometric and concentric contractions for different contraction intensities and muscle lengths. Therefore, the aim was to determine these influences over a wide range of contraction intensities and ankle joint angles for human triceps surae. Additionally, the influence of contraction intensity and ankle joint angle on muscle gearing was evaluated. Ten sport students performed concentric and isometric contractions with intensities between 0 and 90% of the maximum voluntary contraction and ankle joint angles from 50° to 120°. During these contractions, the m. gastrocnemius medialis and lateralis and the m. soleus were recorded via ultrasound imaging. A nonlinear relationship between fascicle length and pennation angle was discovered, which can be described with a quadratic fit for each of the muscles during isometric contraction. A nearly identical relationship was detected during dynamic contraction. The muscle gearing increased almost linearly with contraction intensity and ankle joint angle.

Extending the Asteroseismic Calibration of the Stellar Rossby Number

The stellar Rossby number (Ro) is a dimensionless quantity that is used in the description of fluid flows. It characterizes the relative importance of Coriolis forces on convective motions, which is central to understanding magnetic stellar evolution. Here we present an expanded sample of Kepler asteroseismic targets to help calibrate the relation between Ro and Gaia color, and we extend the relation to redder colors using observations of the mean activity levels and rotation periods for a sample of brighter stars from the Mount Wilson survey. Our quadratic fit to the combined sample is nearly linear between 0.55 < G BP − G RP < 1.2, and can be used to estimate Ro for stars with spectral types between F5 and K3. The strong deviation from linearity in the original calibration may reflect an observational bias against the detection of solar-like oscillations at higher activity levels for the coolest stars.

DCPNet: Deformable Control Point Network for image enhancement

In this paper, we present a novel image enhancement network consisting of global and local color enhancement. The proposed network model is constructed using global transformation functions, which are formed by a set of piece-wise quadratic curves and a local color enhancement network based on the encoder–decoder network. To adaptively and dynamically control the ranges of each piece-wise curve, we introduce deformable control points (DCPs), which determine the overall structure of the global transformation functions. The parameters for piece-wise quadratic curve fitting and DCPs are estimated using the proposed DCP network (DCPNet). DCPNet processes a down-sampled image to derive the DCP parameters: The DCP offsets and the curve parameters. Then, we obtain a set of DCPs from the DCP offsets and connect each adjacent DCP pair by using the curve parameter to construct a global transformation function for each color channel. The original input images are then transformed based on the resulting transformation functions to obtain globally enhanced images. Finally, the intermediate image is fed into the local enhancement network, which has a U-Net architecture, to produce the spatially enhanced images. Extensive experimental results demonstrate the superiority of the proposed method over state-of-the-art methods in various image enhancement tasks, such as image retouching, tone-mapping, and underwater image enhancement.

Exploring a cost-effective and straightforward mechanism for uninterrupted in situ maximum wave runup measurements.

Wave runup, the excess water level above mean sea level, has been measured using different techniques with varying degrees of precision and associated practical limitations. This critical parameter, typically included in coastal assessment studies, varies temporally and spatially and depends on variables that include beach characteristics and nearshore hydrodynamics. Access to continuous datasets, using efficient mechanisms can assist resource-limited regions, such as Caribbean small-island developing states (SIDS), in overcoming coastal resilience obstacles. Experiments were conducted at University College London (UCL) and the University of the West Indies (UWI), which were designed to explore the temporal behaviour of the water surface within the bed during runup events. The experiments encompassed linear waves impacting a static porous bed (UCL) and a moveable granular beach (UWI), with pressure sensors buried at the base of each beach. The analyses showed that the averaged values of the time-varying water elevations within the bed, when spatially presented, produced a quadratic or cubic polynomial fit, where the curves' stationary points were accurate indicators of the location of the maximum runup position at the surface of the bed. In this way, an arrangement of buried pressure sensors can be used as an efficient means to accurately produce a continuous time series of maximum runup positions.This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Pilot protection based on the similarity of the traveling waves between the quadratic fitting curve and the calculated curve for the All-DC wind power transmission system

The All-DC wind power generation system can effectively solve the harmonic resonance problem caused by large-scale wind power AC collection and transmission, gradually becoming a hot topic in future research. However, there are few studies on the relay protection of the All-DC wind power transmission systems. In the All-DC wind power systems, there are differences in topology, control strategies, fault characteristics, boundary characteristics, etc. At the same time, existing pilot protection has problems such as strict information synchronization requirements and selection of setting values through simulation. Therefore, the proposed pilot protection based on the similarity of the traveling wave between the quadratic fitting curve and the calculated curve for the All-DC wind power system transmission lines. Firstly, the difference of the 1-mode initial current waveform characteristics is analyzed in the time domain at both ends. Then, the least squares method is introduced to fit the differential curves of the current forward and backward traveling waves at two terminals. The differential characteristics of the differences between the fitted curve, the calculated curve, and the measured curve under the influence of internal and external errors are analyzed. Finally, the calculated value of traveling wave current during external metallicity fault is used as the standard. By comparing the fitting curve of current traveling waves and the difference in the calculation curve to distinguish internal faults from external faults. The simulation results show that the proposed protection principle can fault resistance of 2200 Ω and noise interference of 20 dB. In addition, the proposed method does not require strict data synchronization, higher sampling frequency, and setting value through simulation.

Leveraging Quadratic Polynomials in Python for Advanced Data Analysis.

This research explores the application of quadratic polynomials in Python for advanced data analysis. The study demonstrates how quadratic models can effectively capture nonlinear relationships in complex datasets by leveraging Python libraries such as NumPy, Matplotlib, scikit-learn, and Pandas. The methodology involves fitting quadratic polynomials to the data using least-squares regression and evaluating the model fit using the coefficient of determination (R-squared). The results highlight the strong performance of the quadratic polynomial fit, as evidenced by high R-squared values, indicating the model's ability to explain a substantial proportion of the data variability. Comparisons with linear and cubic models further underscore the quadratic model's balance between simplicity and precision for many practical applications. The study also acknowledges the limitations of quadratic polynomials and proposes future research directions to enhance their accuracy and efficiency for diverse data analysis tasks. This research bridges the gap between theoretical concepts and practical implementation, providing an accessible Python-based tool for leveraging quadratic polynomials in data analysis.

Soil pH amendment alters the abundance, diversity, and composition of microbial communities in two contrasting agricultural soils.

This study delves into the impact of soil pH on microbial communities, investigating whether pH directly or indirectly influences bacterial and fungal communities. The research involved two contrasting soils subjected to a 1-2 pH unit amendment. Results indicate bacterial community composition was shaped by soil pH through physiological constraints and nutrient limitations. We found that most taxa relative abundances at the phylum and family levels responded to pH with a quadratic fitting pattern, indicating that soil pH is a reliable predictor. Additionally, soil pH was found to significantly influence the predicted abundance of functional genes involved in the nitrogen cycle as well as in methane production and consumption processes. These insights can contribute to develop more effective soil management and conservation strategies.

Evolution of liquid film in a crossflow tunnel: liquid film thickness measurement and effect of droplet impingement on film breakup

Abstract Liquid jet in crossflow tunnel has widespread applications in various industrial devices,&amp;#xD;with the measurements of liquid film on the bottom surface pivotal in exploring relevant mechanisms&amp;#xD;such as heat transfer and film breakup. This work reports the measurements of liquid film on the&amp;#xD;bottom surface of a crossflow tunnel using the brightness-based laser induced fluorescence (LIF)&amp;#xD;method under different flow conditions at ambient pressure and temperature. Film breakup&amp;#xD;phenomena are observed downstream within the tunnel. Employing the shadowgraph method, two&amp;#xD;distinct patterns of film breakup associated with the droplet impingement positions on the film wave&amp;#xD;are identified, i.e., bag breakup and membrane breakup. The film thickness is subsequently calculated,&amp;#xD;and jet impingement and spray impingement of injected liquid on tunnel bottom surface are classified&amp;#xD;based on the centerline film thickness. A critical jet-to-crossflow momentum flux ratio (q) is determined to be proportional to the square of tunnel height. The averaged film thickness across the entire cross-section downstream at a distance of 50 mm from the nozzle is found to increase with the logarithm of q. Besides, the film boundaries are also identified under different flow conditions, which can be well predicted by a quadratic fit with the fitting parameters also correlated to the logarithm of q.&amp;#xD;

A fully automatic curve localization method for extracted spine

The automation of scoliosis positioning presents a challenging and often understated task, yet it holds fundamental significance for the automated analysis of spinal morphological anomalies. This paper introduces a novel spinal curve localization model for precisely differentiating the spinal curves and identifying their concave centers. The proposed model contains three components: i) custom spine central line model, to define the spine central line as a combination of several secant line sequences with different polarities; ii) custom curve model, to classify each spinal curve into one of 11 curves types and deduce each its concave centers by several custom formulas; and iii) adapted distance transform and quadratic line fitting algorithm coupled with custom secant line segment searching strategy (DTQL-LS), to search all line segments in the spine and group consecutive line segments with identical polarity into line sequence. Experimental results show that its positioning success rate is close to 99%. Furthermore, it exhibits significant time efficiency, with the average time to process a single image being less than 30 milliseconds. Moreover, even if some image boundaries are blurred, the center of the curve can still be accurately located.

Comprehensive analysis of electro-mechanical characteristics and new regression models of a novel slanted groove electrical connector

Electrical connectors are crucial electro-mechanical components, with insertion, withdrawal, and electrical contact characteristics serving as key indicators of their reliability. Studying the electro-mechanical characteristics and regression models of electrical connectors is vital to enhance their reliability. This work focuses on the M2-type electrical connector, investigating its electro-mechanical characteristics and developing a regression model. A withdrawal force calculation model is established using cantilever beam theory. Simulation and analysis provide data on insertion force, contact pressure, and contact resistance. Experiments on insertion, withdrawal, and electrical contact are conducted using an insertion force tester and a DC low-resistance instrument, comparing experimental results with simulations. The study reveals the fitting relationship between contact pressure and contact resistance for the M2-type connector. Key findings include a stable fluctuation in contact pressure with a relative error of 1.72% between simulated and tested values, an average discrepancy of 3.81% for insertion force, and 2.38% for withdrawal force, with insertion force slightly higher than withdrawal force. Contact resistance shows a U-shaped trend with pin displacement, with an average experimental error 3.70% and 1.16% lower than theoretical values (4.86%). The new regression model (quadratic polynomial fitting) demonstrates mean absolute percentage errors of 0.1458% for simulation values and 0.2219% for experimental values, significantly lower than those obtained using theoretical formulas (0.7046% and 0.3451%). These results provide theoretical guidance for studying electro-mechanical characteristics and designing experiments for electrical connectors, offering valuable insights for designing and ensuring the reliability of new types of electrical connectors.

Dietary fishmeal substitution with Antarctic krill meal improves the growth performance, lipid metabolism, and health status of oriental river prawn (Macrobrachium nipponense)

Aims to assess the effects of dietary inclusion of Antarctic krill meal (KM), five experimental diets supplemented with graded levels of KM (0 %, FM; 5 %, KM5; 10 %, KM10; 15 %, KM15; 20 %, KM20; 0 %, 13.3 %, 26.7 %, 40.0 %, and 56.7 % replacement fishmeal levels, respectively), were prepared to feed oriental river prawn (Macrobrachium nipponense) (0.20 ± 0.01 g) for 8 weeks. The results revealed significant improvements in weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), and protein efficiency ratio (PER) at the inclusion of 5 %-20 % KM (P < 0.05). In the KM10 and KM15 groups, the concentrations of hemolymph total protein (TP), albumin (ALB), triglycerides (TG), high-density lipoprotein (HDL), and hepatopancreatic glutathione (GSH) were observed to be significantly higher compared to the FM group (P < 0.05). Conversely, the contents of hepatopancreatic malondialdehyde (MDA), total nitric oxide synthase (TNOS), and inducible nitric oxide synthase (iNOS) were significantly lower in the KM10 and KM15 groups compared to the FM group (P < 0.05). The mRNA expression levels of dorsal protein (dorsal), heat shock protein 60 (hsp60), and myeloid differentiation factor 88 (myd88) in the hepatopancreas in the KM10 group exhibited the lowest level. Additionally, compared to the FM group, the expression levels of fatty acid synthase (fas) and acetyl CoA carboxylase (acc) were significantly upregulated (P < 0.05), while the acyl CoA bindingprotein (acbp), carnitine palmitoyltransferase I (cpt I), and scavenger receptor B I (sr-b I) were significantly downregulated in the KM10 group (P < 0.05). In addition, the results of histopathology sections showed that 5–15 % KM could improve the health status of hepatopancreas and was a safe alternative to fishmeal. Overall, the optimal KM inclusion level in feed was 12.96 % (substituting for 34.60 % fishmeal) based on the quadratic fitting curve calculations of WGR and SGR.

A Global Paleosecular Variation Database for the Paleogene: Stationary Secular Variation Behavior Since the Triassic?

AbstractPaleosecular variation analysis is a primary tool for characterizing ancient geomagnetic behavior and its evolution through time. This study presents a new high‐quality directional data set, paleosecular variation of the Paleogene (PSVP), with and without correction for serial correlation, compiled from 1,667 sites from 45 different localities from the Paleogene and late Cretaceous (84–23 Ma). The data set is used to study the variability, structure, and latitude dependence of the geomagnetic field during that period by varying selection criteria and PSV models. Modeled values for the equatorial virtual geomagnetic pole (VGP) dispersion have over‐lapping uncertainty intervals within their uncertainty bounds between 8.3° and 18.6° for the past 250 Ma. We investigate the suitability of two descriptive models of PSV, Model G‐style quadratic fits and covariant Giant Gaussian Process models, and find that both styles of model fail to satisfactorily reproduce the latitude dependent morphology of PSV, but suggest that estimates of the equatorial VGP dispersion may still robustly characterize aspects of Earth's long‐term field morphology. During this time where the PSV behavior has not changed substantially, the reversal frequency has varied widely. The lack of a clear relationship between PSV behavior and reversal frequency is not trivially explained in the context of published findings regarding numerical geodynamo simulations.

High frequency heart rate variability is associated with sensitivity to affective touch

C-tactile afferents (CTs) are a class of unmyelinated, mechanosensitive nerve fibre that respond optimally to skin temperature, slow moving touch typical of a caress. They are hypothesised to signal the rewarding value of affiliative tactile interactions. While CT firing frequency is positively correlated with subjective ratings of touch pleasantness, trait differences in sensitivity to the specific hedonic value of CT targeted touch have been reported.Inter-individual differences in vagally mediated, high frequency heart rate variability (HF-HRV) have been linked to variation in visual social cognition. Thus, the aim of the present study was to examine the relationship between resting state HF-HRV and sensitivity to socially relevant CT targeted touch.58 healthy participants first had a 5-minute electrocardiogram. They then rated the pleasantness of 5 randomly presented velocities of robotically delivered touch. Three velocities fell within (1, 3, 10 cm/s) and two outside (0.3, 30 cm/s) the CT optimal range. Each velocity was delivered twice.On a group level, affective touch ratings were described by a negative quadratic function, with CT optimal velocities rated as more pleasant than slower and faster speeds. Simple regression analysis confirmed participants’ HF-HRV was significantly predicted by the quadratic curve fit of their touch ratings, with higher HF-HRV associated with a better quadratic fit.These findings indicate that, in line with previous observations that higher HF-HRV is associated with enhanced sensitivity to visual social cues, trait differences in autonomic control could account for previously reported individual differences in CT sensitivity.

Parabolic Modeling Forecasts of Space and Time European Hydropower Production

Renewable sources of energy production are some of the main targets today to protect the environment through reduced fossil fuel consumption and CO2 emissions. Alongside wind, solar, marine, biomass and nuclear sources, hydropower is among the oldest but still not fully explored renewable energy sources. Compared with other sources like wind and solar, hydropower is more stable and consistent, offering increased predictability. Even so, it should be analyzed considering water flow, dams capacity, climate change, irrigation, navigation, and so on. The aim of this study is to propose a forecast model of hydropower production capacity and identify long-term trends. The curve fit forecast parabolic model was applied to 33 European countries for time series data from 1990 to 2021. Space-time cube ArcGIS representation in 2D and 3D offers visualization of the prediction and model confidence rate. The quadratic trajectory fit the raw data for 14 countries, validated by visual check, and in 20 countries, validated by FMRSE 10% threshold from the maximal value. The quadratic model choice is good for forecasting future values of hydropower electric capacity in 22 countries, with accuracy confirmed by the VMRSE 10% threshold from the maximal value. Seven local outliers were identified, with only one validated as a global outlier based on the Generalized Extreme Studentized Deviate (GESD) test at a 5% maximal number of outliers and a 90% confidence level. This result achieves our objective of estimating a level with a high degree of occurrence and offering a reliable forecast of hydropower production capacity. All European countries show a growing trend in the short term, but the trends show a stagnation or decrease if policies do not consider intensive growth through new technology integration and digital adoption. Unfortunately, Europe does not have extensive growth potential compared with Asia–Pacific. Public policies must boost hybrid hydro–wind or hydro–solar systems and intensive technical solutions.

Application of Cotton Stalk as an Adsorbent for Copper(II) Ions in Sustainable Wastewater Treatment

The capacity of untreated cotton stalk to remove and adsorb Cu2+ ions in synthetic and natural aqueous solutions was evaluated. The influence of three sensitive parameters of the adsorption process—solution pH, adsorbent dosage, and contact time—on the percentage of Cu2+ removal in agricultural wastewater, livestock wastewater, and synthetic samples was studied. Physicochemical and morphological properties were studied using thermogravimetry, Fourier infrared spectrophotometry, and scanning electron microscopy. The elemental composition, proximal composition, zero charge point, and acid–base sites were determined. In addition, kinetic studies were performed, and the adsorption equilibrium was analyzed. The optimum conditions for Cu2+ adsorption were the following: solution pH = 5.5, adsorbent dosage of 0.6 g, and contact time of 60 min. Under these conditions, the percentage of Cu2+ removal in synthetic samples was 66.5% when the initial copper concentration was 50 mg/L. The removal percentage in agricultural and livestock wastewater samples was 87.60% and 85.05%, respectively, when the initial copper concentration was 25 mg/L. The adsorption data are consistent with the Freundlich isotherm model, which achieved a quadratic fit of 0.991 compared to 0.5542 for the Langmuir model. The experimental results indicate that the adsorption adequately fits the pseudo-second-order kinetic model. The results suggest that cotton stalks are a promising adsorbent for the ecological and economical removal of Cu2+ in wastewater. This research, therefore, provides relevant information that contributes to the sustainable management of agricultural waste and instills hope for a reduction in water pollution from heavy metals derived from agricultural activities.

Distalization and lateralization shoulder angles: do they have a role in predicting postoperative clinical outcomes?

BackgroundLateralization Shoulder Angle (LSA) and Distalization Shoulder Angle (DSA) have been proposed to estimate the appropriateness of reverse shoulder arthroplasty (RSA) positioning. The purpose of this study was to evaluate the predictive value of DSA and LSA over clinical outcomes in a group of patients treated by the same surgeon with the same clinical and radiographic follow-up. MethodsA retrospective analysis of a consecutive series of RSAs performed between 2017 and 2021 was carried out. Inclusion criteria were primary RSA as a treatment for Cuff Tear Arthropathy, Massive Irreparable rotator cuff tear, Osteoarthritis or Rheumatoid arthritis, a true anteroposterior radiograph of the affected shoulder in neutral rotation at final follow-up, a minimum follow-up of 12 months, radiograph used to measure the angles, and clinical evaluation with the same follow-up. Outcome measures were shoulder range of motion (ROM), visual analog scale (VAS) for pain and Constant-Murley score (CS). ResultsA total of 83 patients were included in the study. Patients achieved on average, 130 ± 14.14° of flexion, 97.5 ± 17.67° of abduction, 62.5 ± 3.53° and 72.5 ± 10.60° of external rotation, respectively, at 0° and 90° of abduction, and 5.13° of internal rotation. The mean VAS and CS were, respectively, 2.5 ± 3.5 mm and 69 ± 2.82 points at last follow-up. The mean DSA and LSA were 45 ± 2.72 and 92.99 ± 9.17, respectively. Neither the linear nor the quadratic regression fit for DSA or LSA revealed relevant associations with any of individual ROM measures, except for the quadratic fit correlating LSA and forward flexion (beta = 0.029, P = .027). Linear fit showed a low reverse, but significant, association between DSA and VAS (beta = −0.56, P = .036) and an association of LSA with both CS (beta = −0.344, P = .009) and VAS (beta = 0.091, P = .01). Quadratic models showed higher R squared for all associations, but correlation was significant only between VAS and LSA (beta = 0.006, P = .011) ConclusionWe present the first evaluation of the predictive value of both DSA and LSA in a group of patients treated by the same surgeon with the same clinical and radiographic follow-up. DSA and LSA play only a marginal to no role in the prediction of RSA postoperative ROM and might have a role in predicting VAS and CS.

Suicide in National Collegiate Athletic Association athletes: a 20-year analysis

ObjectivesTo determine the incidence rate of suicide from 2002 to 2022 among athletes from the National Collegiate Athletic Association (NCAA) and assess for potential differences by, sex, race, division and...

Carbonation resistance of recycled fine aggregate concrete reinforced by calcium sulfate whiskers

This study investigates mechanical and carbonation resistance tests conducted on Recycled Fine Aggregate Concrete (RFAC) with three different Recycled Fine Aggregate (RFA) replacement rates and four calcium sulfate whisker (CSW) contents, and investigates the effects of RFA replacement rate and CSW content on the mechanical properties of RFAC and the carbonation resistance of RFAC with calcium sulfate whiskers at different ages of carbonation. The microstructure of CSW-modified RFAC was observed and analyzed by SEM electron microscopy to explore further enhancement and toughening mechanisms of CSW in RFAC, as well as the optimal content of CSW in RFAC. In addition, the carbonation depth of recycled concrete with calcium sulfate beard is modeled based on a quadratic fitting formulation. The test results show that the mechanical properties and carbonation resistance of RFAC would decrease with the increase of the RFA replacement rate. Incorporating CSW can effectively improve the mechanical properties and carbonation resistance of RFAC. At 60 % RFA substitution, CSW at 2 % content has the most significant effect on the mechanical properties and carbonation resistance of RFAC. Microscopic analysis shows that CSW has a bridging effect at the micro-cracks in the concrete matrix, preventing the creation and expansion of micro-cracks in the concrete matrix, thus improving RFAC mechanical properties of RFAC and resistance to carbonation. The predicted results of the carbonation depth model which are constructed from the test data coincide with the results. We can use them to predict and analyze the carbonation depth of the carbonation resistance of recycled concrete.