Characteristic Curve Research Articles

An Integrated 3D DEM Modeling Process for Bimrocks Considering Post‐Peak Behavior and Block Breakage

ABSTRACTBimrocks, a complex rock mass commonly found in geotechnical engineering, are often analyzed through the discrete element method (DEM) to understand their mechanical behavior from both macro and micro perspectives. However, there is limited research addressing the post‐peak behavior of bimrocks, particularly in terms of the uniaxial compression stress–strain curve and failure characteristics, with many studies overlooking the complex nature of their post‐peak behavior. This study proposes a comprehensive method for constructing three‐dimensional (3D) numerical samples of bimrocks and selecting appropriate parameters, focusing on accurately capturing both the post‐peak curve shape and failure characteristics. By combining laboratory tests with CT scanning techniques, numerical samples with structures matching those of the physical samples are created, addressing the issue of block stone breakage in traditional discrete element simulations. The study introduces the selection criteria for matrix and block stone parameters and analyzes the microscopic factors influencing the post‐peak curve and failure characteristics. Results indicate that the damping coefficient and loading rate are crucial in shaping the post‐peak curve, with complex curves requiring multiple damping coefficients. Additionally, the radius multiplier influences crack propagation direction, while the strength ratio affects crack penetration and secondary cracking, with these factors being dependent on the matrix strength.

Full reference point cloud quality assessment using support vector regression

Point clouds are a general format for representing realistic 3D objects in diverse 3D applications. Since point clouds have large data sizes, developing efficient point cloud compression methods is crucial. However, excessive compression leads to various distortions, which deteriorates the point cloud quality perceived by end users. Thus, establishing reliable point cloud quality assessment (PCQA) methods is essential as a benchmark to develop efficient compression methods. This paper presents an accurate full-reference point cloud quality assessment (FR-PCQA) method called full-reference quality assessment using support vector regression (FRSVR) for various types of degradations such as compression distortion, Gaussian noise, and down-sampling. The proposed method demonstrates accurate PCQA by integrating five FR-based metrics covering various types of errors (e.g., considering geometric distortion, color distortion, and point count) using support vector regression (SVR). Moreover, the proposed method achieves a superior trade-off between accuracy and calculation speed because it includes only the calculation of these five simple metrics and SVR, which can perform fast prediction. Experimental results with three types of open datasets show that the proposed method is more accurate than conventional FR-PCQA methods. In addition, the proposed method is faster than state-of-the-art methods that utilize complicated features such as curvature and multi-scale features. Thus, the proposed method provides excellent performance in terms of the accuracy of PCQA and processing speed. Our method is available from https://github.com/STAC-USC/FRSVR-PCQA.

Research on mine curtain strain curve features for its grouting defects identification with ultra-weak fiber Bragg grating

Research on mine curtain strain curve features for its grouting defects identification with ultra-weak fiber Bragg grating

Smart Directional Liquid Manipulation on Curvature-Ratchet Surfaces.

Structured surfaces leverage interfacial energy for directional liquid manipulation without external power, showing tremendous potential in microfluidics, green energy and biomedical applications. While the interplay of interfacial energy between solid surfaces and liquids is crucial for liquid manipulation, a systematic understanding of how the balance in liquid-solid interfacial energy affects liquid behaviors remains lacking. Here, using the curvature-ratchet surface as a generic example, we reveal the complex directional liquid dynamics inherent in the subtle regulation of liquid-solid interfacial energy. We show that curvature and tilt features regulate Laplace pressure asymmetry to enable directional, bidirectional and reverse liquid manipulation. These processes can be modulated by surface free energy and liquid surface tension, and we define their ratio as a new dimensionless number ζ to characterize the liquid-solid interfacial energy relationship. The balanced liquid control happens when ζ ∼ 1, which facilitates versatile liquid behaviors, e.g., fan-shaped spreading, gradient-induced redirection, and back-and-forth transport on various surface array arrangements, all resulting from matching structural designs with the proper ζ. Inspired by this, we showcase an innovative liquid-based information encryption technique, where the liquid displays correct information on preprogrammed surfaces only at designated ζ values. This study lays the groundwork for smart directional liquid manipulation and broadens its application domains.

Characteristics and results of edge-to-edge transcatheter repair of the mitral valve depending on the mechanism causing mitral regurgitation

Abstract Background Transcatheter edge-to-edge repair (TEER) has been increasingly used for selected patients with mitral regurgitation (MR), but limited data are available regarding clinical outcomes in patients with varied mechanisms of MR. Studies usually identify two types of MR: degenerative mitral regurgitation (DMR) and functional mitral regurgitation (FMR). However, patients with mixed MR etiology (MMR) are usually excluded from studies. Objective We investigated baseline echocardiographic data and clinical characteristics of three groups. Additionally, we analized the long-term prognostic impact of TEER in patients with clinically significant MR depending on the mechanism causing MR. Method Patients (n=191) who had severe MR and underwent TEER between November 2011 and Janury 2024 were included in the study. 116 patients with structurally normal mitral leaflets were classified as FMR, while 42 patients with valvular abnormalities were classified as having DMR. 33 patients with both structural and functional deformation were classified as having MMR. Results Baseline echocardiographic and clinical characteristics are summarized in Table 1. Patients with FMR were younger, had fewer comorbidities and had a larger left ventricular size than patients with DMR. Patients with MMR presented intermediate characteristics between patients with FMR and DMR. The median (p25-75) follow-up of patients was 24 (9-50) months. Time-to-event curves of survival in patients with FMR, DMR, MMR was 75% vs. 80% vs. 82%, respectively, and time event-free survival for heart failure hospitalization and all-cause mortality according to severe MR for patients with FMR, DMR, and MMR were 60% vs. 74% vs. 71% (Figure 1). In the follow up, no differences were found in terms of survival and survival free of heart failure admission or all-cause death. Conclusions The baseline characteristics of patients with FMR, DMR and MMR treated with TEER are different. Despite this, the prognosis after treatment is similar in the three groups of patients. Baseline characteristics of patients Kaplan-Meier curves

Parameter influence analysis and optimization of wheel–rail creepage characteristics in high-speed railway curves

PurposeTo investigate the influence of vehicle operation speed, curve geometry parameters and rail profile parameters on wheel–rail creepage in high-speed railway curves and propose a multi-parameter coordinated optimization strategy to reduce wheel–rail contact fatigue damage.Design/methodology/approachTaking a small-radius curve of a high-speed railway as the research object, field measurements were conducted to obtain track parameters and wheel–rail profiles. A coupled vehicle-track dynamics model was established. Multiple numerical experiments were designed using the Latin Hypercube Sampling method to extract wheel-rail creepage indicators and construct a parameter-creepage response surface model.FindingsKey service parameters affecting wheel–rail creepage were identified, including the matching relationship between curve geometry and vehicle speed and rail profile parameters. The influence patterns of various parameters on wheel–rail creepage were revealed through response surface analysis, leading to the establishment of parameter optimization criteria.Originality/valueThis study presents the systematic investigation of wheel–rail creepage characteristics under multi-parameter coupling in high-speed railway curves. A response surface-based parameter-creepage relationship model was established, and a multi-parameter coordinated optimization strategy was proposed. The research findings provide theoretical guidance for controlling wheel–rail contact fatigue damage and optimizing wheel–rail profiles in high-speed railway curves.

Rapid Micro-Motion Feature Extraction of Multiple Space Targets Based on Improved IRT

Micro-motion feature extraction is of great significance for target recognition. However, traditional methods mostly focus on single target and struggle to correctly separate the severely overlapping micro-motion curves of multiple targets. In this paper, a rapid micro-motion feature extraction algorithm of multiple space targets based on inverse radon transform (IRT) with a modified model is proposed. First, the high-resolution range profile (HRRP) generated from echo is subject to binarization to improve the unstable estimation caused by noise. Then, the micro-motion period in a complicated multi-target scenario is obtained by a period estimation method based on the autocorrelation coefficients of binarized HRRP. To further improve the extraction accuracy, the IRT model of the micro-range curve is modified from the sine function to second-order sine function. By searching for the remaining unknown parameters in the model in conjunction with the period, the precise micro-range curves are quickly separated. Each time the curves of a target are extracted, they are removed, and the next extraction is carried out until all the targets have been searched. Finally, simulation and experimental results indicate that the proposed algorithm can not only correctly separate the micro-motion feature curves of multiple space targets under low signal-to-noise ratio (SNR) conditions but also significantly outperforms the original IRT in terms of extraction speed.

Research on Trajectory Planning Method Based on Bézier Curves for Dynamic Scenarios

With the increase in car ownership, traffic congestion, and frequent accidents, autonomous driving technology, especially for dynamic driving scenarios in the whole domain, has become a technological challenge for today’s researchers. Trajectory planning, as a crucial component of the autonomous driving technology framework, is gradually becoming a hot topic in intelligent research. In response to the challenges of planning lane-changing trajectories in complex dynamic driving scenarios under emergency evasive maneuvers, where it is difficult to consider surrounding vehicles and achieve dynamic adaptability, this paper proposes a dynamic adaptive trajectory planning method based on Bézier curves. Firstly, a mathematical model of Bézier curves is established and its curve characteristics are analyzed, which facilitates the correlation between the trajectory control points and the vehicle and the surrounding obstacles. Secondly, a mathematical function representing the Bézier curve is formulated, where the control points serve as the input and the lane-changing control curve as the output. Finally, the proposed method is validated through simulations on a jointly established simulation platform. The results indicate that the proposed method can plan lane-changing trajectories that are both safe and efficient under emergency evasive maneuvers, considering both static and complex dynamic conditions. This provides a novel solution for lane-changing trajectory planning in emergency evasive maneuvers for autonomous vehicles and holds significant theoretical research value.

The learning curve of totalrobotic jejunojejunostomy duringcholedochal cystexcision in pediatrics: a retrospective study.

We conducted this retrospective study to investigate the characteristics of the learning curve of totalrobotic jejunojejunostomy duringcholedochal cystexcision in pediatrics. The study analyzed a database of medical records from the first 54 consecutive patients who underwent total robotic jejunojejunostomy during choledochal cyst excision by a single surgeon. Baseline information and postoperative outcomes were collected, and learning curves were assessed using the cumulative sum (CUSUM) method. Patients were then divided into two groups (A and B) based on the learning curve's cut-off points, and the intraoperative characteristics and postoperative outcomes were compared between the two groups. CUSUM plots revealed that the cut-off point of the learning curve was 17 cases. The operative time of jejunojejunostomy in group A was (61.71 ± 13.47min), which was longer than that of group B (42.43 ± 2.97min) (p < 0.0001). No statistically significant differences were found in terms of the intraoperative bleeding, time to start diet after surgery, hospital stay, and total complications between the two groups (p > 0.05). The learning curve for total robotic jejunojejunostomy during choledochal cyst excision in pediatrics is 17 cases, which can serve as the basis for performance guidance during future training.

Morphological, thermal, optical, and electronic characteristics of PVA/PVP filled WO3 nanocomposites

PVA/PVP filled Tungsten oxide (WO3) nanoparticles hybrid polymer nanocomposites are fabricated using a simple solution casting technique. The XRD, FTIR, and SEM images signify the effective incorporation of WO3 nanoparticles (NPs) in the PVA/PVP mix host matrix. PXRD study indicated that the incorporation of WO3 nanoparticle concentrations up to 3 wt. percent in the host matrix mix upsurges the crystallinity of the polymer nanocomposites. FTIR spectroscopy confirms the existence of intermolecular hydrogen bond formation amongst nanoparticles and the PVA/PVP matrix. SEM analysis demonstrates the WO3 nanoparticles were evenly distributed in the PVA/PVP mix matrix. The tangent loss curve's characteristics for different WO3 doping concentrations indicate that PVP-PVA/(x)WO3 nanocomposites represent both relaxations and non-relaxation dipoles. The tangent loss has a relatively steady value above 0.1 MHz, with a minimal value of 0.09208 at x = 3 wt% loading concentration. The result suggests that the nanocomposite functions as a substance with no loss. The capacitance (Cp) among two electrodes on the bottom and top sides of the nanocomposites was evaluated at pressures varying from 80 to 200 bar to explore the application of the pressure sensor. Thermal evaporation of PVA/PVP:WO3 nanocomposites yielded the changing oxygen vacancy percentage as the WO3 level rose. The moisture-resistant performance of PVA/PVP: WO3 nanocomposites ranged from negative to positive. The PVA/PVP:WO3 nanocomposites has shown its significance in fabricating material for optoelectronic devices including humidity sensors. The nanocomposite for x = 3 wt% is thermally stable in all test ranges up to 890 °C. The findings indicate that WO3 in the produced films improved their thermal stability.

Investigation of the Suitability of the DTV Method for the Online SoH Estimation of NMC Lithium-Ion Cells in Battery Management Systems

Investigating the temperature behavior of lithium-ion battery cells has become an important part of today’s research and development. The main reason for this is that the temperature profile of a battery cell changes during aging. By using Differential Thermal Voltammetry (DTV), new possibilities are opened up, especially since this diagnostic method is designed to work in operando by only requiring voltage and temperature readings. In this study, a batch of NMC-21700 cells were aged in calendar and cyclic manners. After a specified aging cycle was complete, a check-up measurement was performed. During this time, the cycler collected the electrical measuring values, while a negative temperature coefficient thermistor, which was located on the cell, was used to record the temperature fluctuations. The data were then evaluated by using the DTV analysis technique. By comparing the characteristic points of DTV, correlations between the changing curve characteristics and the capacity loss, and therefore the aging of the respective cell, were established. Based on these results, a simple model suitable for online State of Health (SoH) is derived and validated, showing an estimation accuracy of 1.1%.

Study on the mechanical response characteristics of sandstone under elasticity plasticity and full path unloading after peak stress

When underground tunnels in coal mines traverse geological structurally abnormal zones (faults, collapse columns, fractured zones, etc.), excavation-induced unloading leads to instability and failure of the engineering rock mass. Rock masses in fractured zones are in elastic, plastic, and post-peak stress states, and the process of excavation through these zones essentially involves unloading under full stress paths. To explore the mechanical response of sandstone under different stress levels, based on the investigation of possible stress paths, a systematic study is conducted on various unloading paths, including elastic-axial compression with unloading of confining pressure, elastic-constant principal stress with unloading of confining pressure, plastic-axial compression with unloading of confining pressure, plastic-constant principal stress with unloading of confining pressure, plastic-constant axial D1 displacement with unloading of confining pressure, plastic-equal proportional unloading of axial and confining pressures, and post-peak-synchronous unloading of axial and confining pressures. Characteristics of full stress-strain curves under seven unloading paths are obtained. The deformation patterns caused by unloading are analyzed, and the relationship between unloading paths and strain increments is investigated. Results show that, as the degree of unloading increases, the unloading deformation modulus ( E ) in the elastic stress state exhibits a trend of initial increase, then stabilization, followed by decrease, while in the plastic stress state, E gradually decreases. Both elastic and plastic states show an increasing trend in Poisson’s ratio (µ). The normalized plastic shear strain γp/γpmax and dilation angle (ψ) conform to a single exponential function, and there is a negative correlation between initial confining pressure and dilation angle. These findings support the enrichment and development of unloading rock mechanics.

Deformation theory and energy mechanism of cyclic dynamic mechanical damage for granite in the diversion tunnel under cyclic loading-unloading.

The diversion tunnel is frequently subjected to cyclic dynamic loads during blasting and mechanical excavation. To explore the theory and mechanism of cyclic dynamic mechanical damage for granite in a diversion tunnel under cyclic loading-unloading, the incremental cyclic loading-unloading test and numerical simulation were conducted on granite samples from the diversion tunnel. According to the mechanical and deformation characteristics of rock samples in the process of cyclic loading-unloading, the stress-strain normalization theory evolution model based on viscoelastoplasticity was established, and the cyclic dynamic damage evolution mechanism of rock samples was revealed. The evolution characteristics of stress-strain curves of rock samples under cyclic loading-unloading were effectively described, and the loading-unloading two-stage constitutive equation of rock samples under cyclic loading-unloading was established. The energy and damage evolution mechanism of the final full stress-strain curve and the influence mechanism of shrinkage and expansion of rock particles on the mechanical properties of granite were discussed.

Investigation of the Influence of Image Reconstruction Parameters to Improve the Ability to Depict Internal Tumor Necrosis

There are attempts to assess tumor heterogeneity by texture analysis. However, the ordered subsets-expectation maximization (OSEM) reconstruction method has problems depicting heterogeneities. The aim of this study was to identify image reconstruction parameters that improve the ability to depict internal tumor necrosis using a self-made phantom that simulates internal necrosis. Self-made phantoms were prepared using polypropylene cylinders with inner diameters of 18.0 mm and 6.0 mm. The concentration ratios of the simulated tumor : tumor interior were 4 : 0 and 4 : 1. For each reconstruction method, the iteration for OSEM and OSEM+point spread function (PSF) were 1 to 25 and the subset was 12. The β values for block sequential regularized expectation maximization (BSREM) were set between 10 and 400. We evaluated the features of the profile curve, contrast-to-noise ratio, and grey-level co-occurrence matrix (GLCM). In the phantom study, OSEM and OSEM+PSF showed a better delineation of the differences between the inside and outside of the cylinder as iteration was increased and BSREM showed a better delineation as β was decreased. The highest value for each feature, both 4 : 0 and 4 : 1, was BSREM β 10 for angular second moment (ASM) and inverse differential moment (IDM), OSEM iteration 25 for contrast and entropy. We have identified image reconstruction parameters that improve the ability to visualize internal tumor necrosis. The parameter was BRSEM β 10.

Stochastic simulation of soil moisture dynamics in farmland in the eastern region of the Songnen Plain.

Soil moisture is the core of the hydrological cycle in agroecosystems, and most of the studies on soil moisture dynamics modeling adopt deterministic research methods, which are not well suited to study the hydrological processes in agricultural fields under changing conditions. Therefore, the present study adopts a stochastic approach to reveal the distribution characteristics of soil moisture in agroecosystems under the effects of soil, climate, vegetation, and other influencing factors. Using soil moisture and precipitation data and based on a stochastic model of soil moisture dynamics, the point-scale soil moisture dynamic characteristics and soil moisture probability density function of farmland systems in the Songnen Plain region were investigated. The soil moisture of maize in the study area showed a certain degree of stochasticity, and the curve characteristics of the probability density function of soil moisture p(s) obtained from the simulation were very close to those of the measured p(s). It shows that the stochastic model can effectively simulate the probability density function of soil moisture in the study area, which can provide a theoretical basis and scientific method for efficiently using soil and water resources in the area.

Numerical study on infrared suppression (IRS) devices with streamlined lobed nozzles featuring Bezier curve characteristics

Numerical study on infrared suppression (IRS) devices with streamlined lobed nozzles featuring Bezier curve characteristics

Prognostic value of the fibrinogen-to-albumin ratio (FAR) in patients with chronic heart failure across the different ejection fraction spectrum

ABSTRACT The ratio of fibrinogen to albumin (FAR) is considered a new inflammatory biomarker and a predictor of cardiovascular disease risk. However, its prognostic value for patients with chronic heart failure (CHF) with different ejection fractions (EFs) remains unclear. A total of 916 hospitalized patients with CHF from January 2017 to October 2021 in the First Affiliated Hospital of Kunming Medical University were included in the study. Death occurred in 417 (45.5%) patients out of 916 patients during a median follow-up time of 750 days. Among these patients, 381 patients suffered from HFrEF (LVEF <40%) and 535 patients suffered from HFpEF or HFmrEF (HFpEF plus HFmrEF, LVEF ≥ 40%). Patients were categorized into high-level FAR (FAR-H) and low-level FAR (FAR-L) groups based on the optimal cut-off value of FAR (9.06) obtained from receiver operating characteristic (ROC) curve analysis. Upon analysing the Kaplan – Meier plots, the incidence of death was significantly higher in all patients with FAR-H and patients in both HF subgroups (p < 0.001). The multivariate Cox proportional hazard analyses indicated that the FAR was an independent predictor of all-cause mortality, regardless of heart failure subtype. (HR 1.115, 95% CI 1.089–1.142, p < 0.001; HFpEF plus HFmrEF, HR 1.109, 95% CI 1.074–1.146, p < 0.0001; HFrEF, HR 1.138, 95% CI 1.094–1.183, p < 0.0001) The optimal cut-off value of FAR in predicting all-cause mortality was 9.06 with an area under the curve value of 0.720 (95% CI: 0.687–0.753, p < 0.001), a sensitivity of 68.8% and a specificity of 65.6%. After adjusting for the traditional indicators (LVEF, Lg BNP, etc.), the new model with the FAR had better prediction ability in patients with CHF. Elevated FAR is an independent predictor of death in CHF and is not related to the HF subtype.

Study on the Properties of Basalt Fiber-Calcined Gangue-Silty Clay Foam Concrete for Filling Undermined Goaf Areas of Highways.

The collapse of surface goaf beneath highways can result in instability and damage to roadbeds. However, filling the goaf areas with foam concrete can significantly enhance the stability of the roadbeds while considerably reducing the costs of filling materials. This study analyzes the effects on destructive characteristics, mechanical properties, stress-strain curve features, and relevant metrics, while also observing the microstructure of basalt fiber-calcined gangue-silty clay foam concrete (BF-CCG-SCFC). The results indicate that the water-binder ratio significantly influences the cubic compressive strength, split tensile strength, and fluidity of BF-CCG-SCFC. Silty clay reduces the cubic compressive strength, split tensile strength, and fluidity of BF-CCG-SCFC. Conversely, an appropriate amount of calcined gangue and basalt fiber significantly increases the cubic compressive strength and split tensile strength, while decreasing fluidity. To satisfy the strength and fluidity requirements of the filler material in hollow areas, the optimal water-binder ratio for BF-CCG-SCFC is 0.55, the ideal mixing ratio of calcined gangue to silty clay is 2:2, and the basalt fiber content should be 1%. The study examines the influence of varying water-binder ratios, the combined proportions of calcined gangue and silty clay, and different basalt fiber contents on the elastic modulus, peak stress, and peak strain of BF-CCG-SCFC. Additionally, the water-binder ratio influences the matrix strength through the non-hydration reactions of doped particles, while gangue and clay induce a "gradient hydration effect" during the hydration process. The incorporation of basalt fibers enhances the mechanical interlocking between the fibers and the matrix.

Study on the dual-segment arctangent model of magnetorheological damper (MRD)

Abstract Magnetorheological fluid damper (MRD) is a damping device that utilizes the instantaneous variable characteristics of magnetorheological fluid (MRF) in magnetic field to control damping force. At present, there are some problems with the existing mechanical parametric models of MRD, such as the complexity of parameters in the Bouc-Wen model, low model accuracy, and the inability of the Bingham model to accurately capture the hysteresis characteristics of damping force with velocity variation. In response to these issues, on the base of MRD performance testing, a dual-segment arctangent model based on arctangent function is proposed. This model uses the arctangent function to describe the nonlinearity of the damping force output curve. And using piecewise fitting method to accurately capture the hysteresis characteristics of the output curve. Compared with existing parametric models such as the Bingham model, Sigmoid model, Bouc-wen improved model, et.al., the dual-segment arctangent model shows simpler parameters and higher model fitting accuracy. The comparative analysis of the fitting results based on experimental data confirms the effectiveness and accuracy of the proposed model, providing valuable reference for the development of high-precision MRD mechanical models.&amp;#xD;

Development of a Generalized Partition Curve Model for Hydrocyclones

ABSTRACT Partition curves associated with hydrocyclone classification processes have been known to deviate from the typical S-shape by exhibiting asymmetric and non-monotonic behaviors, making their mathematical modeling challenging. In addition to the well-documented phenomenon of fish-hooks at the finer end, the partition curves can also sometimes exhibit fat-tailed behavior at the coarser end of the size spectrum, which has not been extensively highlighted in the literature. This study aimed to develop a parametric model for the partition curves which can systematically and effectively accommodate both these irregularities at the coarser and finer ends. Instead of adopting a piece-wise modeling approach for the task, a continuous model was successfully developed in the form of the addition of three component functions, each affecting different regions and features of the partition curve with a total of 7 fitting parameters. Two of the component functions were modified versions of the cumulative density functions of the Weibull distribution while the third was the modified solution of a single hyperbolic branch having a horizontal and a slant asymptote to accommodate the observed fat-tailed behavior. The model exhibited remarkable fitting performance for both experimentally generated and literature data. An alternative method of defining the separation cut size has also been proposed in this study to overcome the limitations of the classical concept of the d50. It was also shown how the developed model can be utilized for quantitative analysis of the critical aspects of the partition curve such as the cut size, bypass, and the dip point.