Search Results (118)

Background: Although B vitamins are implicated in cardiovascular regulation, the associations between serum thiamine (vitamin B1) and blood pressure (BP) remain unclear, particularly among women who are at high risk for hypertension-related complications. This study aimed to investigate relationships between serum thiamine levels and BP outcomes among middle-aged and elderly women in eastern China. Methods: A community-based cross-sectional study was conducted among 2015 women aged 45–69 years in Zhejiang Province, China. Serum thiamine levels were quantified using liquid chromatography tandem mass spectrometry (LC-MS/MS). Hypertension was defined as measured BP ≥ 140/90 mmHg, or current use of antihypertensive medications. Multivariate logistic and linear regression models were used to assess associations of thiamine with hypertension prevalence and BP levels, respectively. Dose–response relationships were evaluated using restricted cubic splines (RCSs). Results: Higher thiamine levels were significantly associated with reduced hypertension prevalence (adjusted OR per SD increase: 0.87; 95%CI: 0.77, 0.97), with RCSs confirming linear dose–response (p-overall < 0.05, p-nonlinearity > 0.05). Compared with the lowest tertile, participants in the highest thiamine tertile had a 25% lower hypertension risk. Thiamine levels also showed negative associations with systolic BP (adjusted coef: −1.51 mmHg per SD; 95% CI: −2.33, −0.68), with the participants in the highest tertile showing a 3.94 mmHg reduction (95%CI: −5.97, −1.92). No significant relationship was found for diastolic BP. Conclusions: Serum thiamine is inversely associated with both hypertension prevalence and systolic BP in middle-aged and elderly women. This study supports the potential of serum thiamine as a modifiable biomarker in hypertension prevention strategies, particularly among aging women. Full article

Transfinite interpolation, originally proposed in the early 1970s as a global interpolation method, was first implemented using Lagrange polynomials and cubic Hermite splines. While initially developed for computer-aided geometric design (CAGD), the method also found application in global finite element analysis. With the advent of isogeometric analysis (IGA), Bernstein–Bézier polynomials have increasingly replaced Lagrange polynomials, particularly in conjunction with tensor product B-splines and non-uniform rational B-splines (NURBSs). Despite its early promise, transfinite interpolation has seen limited adoption in modern CAD/CAE workflows, primarily due to its mathematical complexity—especially when blending polynomials of different degrees. In this context, the present study revisits transfinite interpolation and demonstrates that, in four broad classes, Lagrange polynomials can be systematically replaced by Bernstein polynomials in a one-to-one manner, thus giving the same accuracy. In a fifth class, this replacement yields a robust dual set of basis functions with improved numerical properties. A key advantage of Bernstein polynomials lies in their natural compatibility with weighted formulations, enabling the accurate representation of conic sections and quadrics—scenarios where IGA methods are particularly effective. The proposed methodology is validated through its application to a boundary-value problem governed by the Laplace equation, as well as to the eigenvalue analysis of an acoustic cavity, thereby confirming its feasibility and accuracy. Full article

Background: The Pearl River Delta (PRD) region in Guangdong, China, is urbanized and economically significant. Rapid development has shaped diverse dietary habits. In this densely populated area, there is an urgent need to assess vitamin status and its impact on age-related diseases. Methods: A total of 2646 participants (age: 50.92 ± 9.30 years; male: 64.06%) were recruited from the Pearl River Delta (PRD) region. Participants were included from 1 December 2020 to 30 November 2021. Three restricted cubic spline logistic models, interaction terms, and mediated effects analyses were used to assess the association between vitamin A, B, E, B₁, B₂, B₃, B₅, B₆, and B₉ between five age-related diseases: cerebrovascular disease (CVD), coronary heart disease (CHD), hypertension (HTN), dyslipidemia (DYS), and type 2 diabetes mellitus (T2DM). Results: Blood concentrations of nine vitamins showed a right-skewed distribution. Significant correlations were found between vitamin levels and age-related diseases across nine groups (p < 0.05). A J-shaped relationship was observed between vitamin levels and the risk of age-related diseases, except for the Vitamin A-HTN/T2DM, which showed Maximum Effective Concentration (MEC). Specific thresholds included: Vitamin A: 1080 ng/mL (DYS); Vitamin B₁: 77 ng/mL (CVD), 75.5 ng/mL (HTN); Vitamin B₅: 900 ng/mL (CVD), 600 ng/mL (HTN), 690 ng/mL (DYS); Vitamin B₆: 82 ng/mL (CVD). The protective effect of vitamins against age-related diseases decreased with age, and higher levels of vitamins A and B₁ correlated with increased hypertension risk in older adults (P_interaction < 0.01). Low Body Resilience Index (BRI) and physical activity mediated the protective effects of vitamins A and B₅ on HTN and DYS, while no mediating effects were found for smoking and alcohol consumption. Conclusions: The effectiveness of multivitamin supplementation in preventing cardiovascular, cerebrovascular, and metabolic diseases may be limited in healthy aging populations. Health professionals should consider patients’ physiological conditions and blood vitamin levels to avoid overdose. More interventional studies are needed to establish causal relationships. Full article

To address the challenge of optimizing system adaptability, disturbance rejection, control precision, and convergence speed simultaneously in four-wheel steering (4WS) stability control, a 4WS controller with a variable steering ratio (VSR) strategy and fast adaptive super-twisting (FAST) sliding mode control is proposed to control and output the steering angles of four wheels. The ideal VSR strategy is designed based on the constant yaw rate gain, and a cubic quasi-uniform B-spline curve fitting method is innovatively used to optimize the VSR curve, effectively mitigating steering fluctuations and obtaining precise reference front wheel angles. A controller based on FAST is designed for active rear wheel steering control using a symmetric 4WS vehicle model. Under double-lane change conditions with varying speeds, the simulations show that, compared with the constant steering ratio, the proposed VSR strategy enhances low-speed sensitivity and high-speed stability, improving the system’s adaptability to different operating conditions. Compared with conventional sliding mode control methods, the proposed FAST algorithm reduces chattering while increasing convergence speed and control precision. The VSR-FAST controller achieves optimization levels of more than 7.3% in sideslip angle and over 41% in yaw rate across different speeds, achieving an overall improvement in the stability control performance of the 4WS system. Full article

This paper proposes an enhanced RRT* algorithm (XN-RRT*) to address the challenges of low path planning efficiency and suboptimal picking success rates in complex pitaya harvesting environments. The algorithm generates sampling points based on normal distribution and dynamically adjusts the center and range of the sampling distribution according to the target distance and tree density, thus reducing redundant sampling. An improved artificial potential field method is employed during tree expansion, incorporating adjustment factors and target points to refine the guidance of sampling points and overcome local optima and infeasible targets. A greedy algorithm is then used to remove redundant nodes, shorten the path, and apply cubic B-spline curves to smooth the path, improving the stability and continuity of the robotic arm. Simulations in both two-dimensional and three-dimensional environments demonstrate that the XN-RRT* algorithm performs effectively, with fewer iterations, high convergence efficiency, and superior path quality. The simulation of a six-degree-of-freedom robotic arm in a pitaya orchard environment using the ROS2 platform shows that the XN-RRT* algorithm achieves a 98% picking path planning success rate, outperforming the RRT* algorithm by 90.32%, with a 27.12% reduction in path length and a 14% increase in planning success rate. The experimental results confirm that the proposed algorithm exhibits excellent overall performance in complex harvesting environments, offering a valuable reference for robotic arm path planning. Full article

This paper presents a novel gait design for serpentine robots to smoothly wrap around and traverse vibration-damping hammers along overhead power lines. Cubic quasi-uniform B-spline curves are utilized to seamlessly transition between helical segments of varying diameters during obstacle crossing, effectively reducing motion-induced impacts. The design begins by determining the control points of the B-spline curves to ensure posture continuity and prevent collisions with surrounding hardware obstacles, resulting in the derivation of an obstacle-crossing curve equation. Using this equation, the node coordinates and postures of individual robot units are computed, followed by the calculation of joint angles via inverse kinematics. A dual-chain Hopf oscillator is then employed to generate the obstacle-crossing gait. The feasibility of the proposed gait is validated through simulations in CoppeliaSim and Simulink, which model the robot’s motion as it wraps around and crosses eccentric obstacles with varying diameters. Additionally, a simulation platform is developed to analyze variations in joint angles and angular velocities during obstacle traversal. Results demonstrate that the gait, generated by combining cubic quasi-uniform B-spline curves with a dual-chain Hopf oscillator, achieves smooth and stable wrapping and crossing of vibration-damping hammers. The robot exhibits no abrupt changes in joint angles, smooth angular velocity profiles without sharp peaks, and impact-free joint interactions, ensuring reliable performance in complex environments. Full article

This paper proposes an improved RRT*-Connect algorithm (IRRT*-Connect) for robotic arm path planning in narrow environments with multiple obstacles. A heuristic sampling strategy is adopted with the integration of the ellipsoidal subset sampling and goal-biased sampling strategies, which can continuously compress the sampling space to enhance the sampling efficiency. During the node expansion process, an adaptive step-size method is introduced to dynamically adjust the step size based on the obstacle information, while a node rejection strategy is used to accelerate the search process so as to generate a near-optimal collision-free path. A pruning optimization strategy is also proposed to eliminate the redundant nodes from the path. Furthermore, a cubic non-uniform B-spline interpolation algorithm is applied to smooth the generated path. Finally, simulation experiments of the IRRT*-Connect algorithm are conducted in Python and ROS, and physical experiments are performed on a UR5 robotic arm. By comparing with the existing algorithms, it is demonstrated that the proposed method can achieve shorter planning times and lower path costs of the manipulator operation. Full article

Urban drone applications require efficient path planning to ensure safe and optimal navigation through complex environments. Drawing inspiration from the collective intelligence of animal groups and electoral processes in human societies, this study integrates hierarchical structures and group interaction behaviors into the standard Particle Swarm Optimization algorithm. Specifically, competitive and supportive behaviors are mathematically modeled to enhance particle learning strategies and improve global search capabilities in the mid-optimization phase. To mitigate the risk of convergence to local optima in later stages, a mutation mechanism is introduced to enhance population diversity and overall accuracy. To address the challenges of urban drone path planning, this paper proposes an innovative method that combines a path segmentation and prioritized update algorithm with a cubic B-spline curve algorithm. This method enhances both path optimality and smoothness, ensuring safe and efficient navigation in complex urban settings. Comparative simulations demonstrate the effectiveness of the proposed approach, yielding smoother trajectories and improved real-time performance. Additionally, the method significantly reduces energy consumption and operation time. Overall, this research advances drone path planning technology and broadens its applicability in diverse urban environments. Full article

The tubercles on the flipper of humpback whales are beneficial for improving their locomotion performance. Based on biomimetic design, the bulge model was developed to mimic this function through cubic B-spline curve fitting, aiming to improve the stall performance of the two-element wingsail. The numerical calculation method was validated against experiments to ensure the reliability of the numerical results. Five models of the bulges of the main wing were developed, and the influence of different bulges on the stall performance of the two-element wingsail under logarithmic gradient wind conditions was examined. By analyzing its lift and drag characteristics, pressure load distribution, and flow field near the stall angle, the mechanism by which the bulges improved the stall characteristics of the two-element wingsail was revealed. The result indicated that the two-element wingsail in the Case 5 scheme has a maximum lift coefficient of 1.25, and that the lift reduction in the early stage of stall is only 8.8%, which is 43.6% less than the original wingsail lift reduction. As the bulge size increases the strength of the forward vortex created by the middle larger bulge increases, resulting in the absence of a symmetrical vortex structure on the suction surface of the wingsail, causing high fluid momentum band deflection. The energy of the boundary layer is supplemented by vorticity transport, promoting the formation of attached flow on the side of the smaller bulge and improving the lift coefficient. Full article

This work aims to provide approximate solutions for singularly perturbed problems with periodic boundary conditions using quintic B-splines and collocation. The well-known Shishkin mesh strategy is applied for mesh construction. Convergence analysis demonstrates that the method achieves parameter-uniform convergence with fourth-order accuracy in the maximum norm. Numerical examples are presented to validate the theoretical estimates. Additionally, the standard hybrid finite difference scheme, a cubic spline scheme, and the proposed method are compared to demonstrate the effectiveness of the present approach. Full article

The static aeroelastic characteristics of the distributed propulsion wing (DPW) were studied using the CFD/CSD loose coupling method in this study. The momentum source method of the Reynolds-averaged Navier–Stokes equation based on the k-ω SST turbulence model solution was used as the CFD solution module. The upper and lower surfaces of the DPW were established using the cubic B-spline basis function method, and the surfaces of the inlet and outlet were established using the fourth-order Bezier curve. Finally, a three-dimensional parametric model of the DPW was established. A structural finite-element model of the DPW was established, a multipoint array method program based on the three-dimensional radial basis function (RBF) was written as a data exchange module to realize the aerodynamic and structural data exchange of the DPW’s static aeroelastic analysis process, and, finally, an aeroelastic analysis of the DPW was achieved. The results show that the convergence rate of the CFD/CSD loosely coupled method is fast, and the structural static aeroelastic deformation is mainly manifested as bending deformation and positive torsion deformation, which are typical static aeroelastic phenomena of the straight wing. Under the influence of static aeroelastic deformation, the increase in the lift characteristics of the DPW is mainly caused by the slipstream region of the lower surface and the non-slipstream region of the upper and lower surface. Meanwhile, the increase in its nose-up moment and the increase in the longitudinal static stability margin may have an impact on the longitudinal stability of the UAV. To meet the requirements of engineering applications, a rapid simulation method of equivalent airfoil, which can be applied to commercial software for analysis, was developed, and the effectiveness of the method was verified via comparison with the CFD/CSD loose coupling method. On this basis, the static aeroelastic characteristics of the UAV with DPWs were studied. The research results reveal the static aeroelastic characteristics of the DPW, which hold some significance for engineering guidance for this kind of aircraft. Full article

Background: Chronic hepatitis B (CHB) in children presents a significant global health challenge, with liver inflammation and fibrosis being critical concerns for disease progression and long-term outcomes. Methods: This retrospective study analyzed 1629 pediatric CHB patients from the Fifth Medical Center of Chinese PLA General Hospital, spanning from January 2000 to December 2021. Liver biopsies were performed to assess the severity of liver inflammation and fibrosis, which were graded using the Scheuer scoring system. Key clinical indicators, including age, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT), were evaluated for their predictive value in determining disease severity using restricted cubic spline regression models. Results: Significant nonlinear associations were found between the clinical indicators and liver pathology. Older age was strongly associated with increased risks of moderate to severe inflammation (OR 2.21, 95% CI: 1.34–3.63, p = 0.002) and significant fibrosis (OR 2.22, 95% CI: 1.31–3.77, p = 0.003). Elevated ALT levels (≥80 U/L) were correlated with a higher likelihood of moderate to severe inflammation (OR 1.82, 95% CI: 1.05–3.15, p = 0.033), while higher GGT levels (≥50 U/L) were significantly associated with advanced fibrosis (OR 2.62, 95% CI: 1.72–3.99, p < 0.001). Conclusions: Regular monitoring of clinical indicators such as ALT, AST, and GGT levels plays a critical role in identifying pediatric CHB patients at higher risk of moderate to severe inflammation and significant fibrosis. Our findings highlight the value of integrating age and key biochemical markers into non-invasive diagnostic algorithms for the early detection and management of liver pathology in children. Full article

The risk-neutral density is a fundamental concept in pricing financial derivatives, risk management, and assessing financial markets’ perceptions over significant political or economic events. In this paper, we propose a new nonparametric method for estimating the risk-neutral density using natural cubic splines (NCS). The estimated density is twice continuously differentiable with linear tails at both ends. Our method targets the logarithm of the underlying asset price, releasing the restriction to the positive domain. We theoretically prove the consistency of our NCS method. We conduct a comprehensive empirical study comparing the proposed NCS method with a piecewise constant method, a uniform quartic B-spline method, and a cubic spline method from the literature using 20 years of S&P 500 index option data. The empirical results show that our NCS method is more robust than the piecewise constant method, which can only produce a discontinuous density, especially for options with maturities longer than six months. Moreover, our NCS method outperforms other historical continuous methods in terms of optimization feasibility and option price estimation. Full article

To improve the safety and reliability of robotic manipulators during high-speed precision movements, this paper proposes a method for smooth and time-optimal trajectory planning incorporating kinodynamic constraints. The primary objective is to use an evolutionary algorithm to determine a trajectory by considering time and jerk within the feasible path-pseudo-velocity phase plane region. Firstly, the path parameterization theory extracted the maximum pseudo-velocity projection curve from the kinodynamic constraints. Subsequently, the feasible region in the phase plane was defined through reachability analysis of discrete linear systems. Thereafter, we constructed the trajectory function using a cubic B-spline curve, optimizing its control points with an improved carnivorous plant optimization algorithm. Finally, the effectiveness and practicality of this method were verified through simulations on a 6-DOF manipulator. Full article

Background: Studies on the association between serum vitamin B₆ status and colorectal cancer prognosis are limited and have yielded inconsistent results. This study investigated the association of pyridoxal 5′-phosphate (PLP) and pyridoxic acid ratio (PAr) index with colorectal cancer survival. Methods: A total of 1286 colorectal cancer patients diagnosed since 2010 were selected from the Guangdong Colorectal Cancer Cohort study. Serum levels of PLP, pyridoxal, and 4-pyridoxic acid were measured using ultra-high-performance liquid chromatography–tandem mass spectrometry. The study followed overall mortality and colorectal cancer-specific mortality until December 2023. Multivariable Cox proportional hazards regression models were applied to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs). Restricted cubic spline and stratified analysis were performed. Results: During a median follow-up of 77.36 months, 331 deaths were recorded, with 293 specifically attributed to colorectal cancer. Higher PLP levels were associated with a longer overall survival (HR_{Q4 vs. Q1}, 0.63; 95% CI: 0.46, 0.87; p for trend = 0.008) and colorectal cancer-specific survival (HR_{Q4 vs. Q1}, 0.62; 95% CI: 0.44, 0.87; p for trend = 0.006). Non-linear associations were observed between serum PLP and overall and colorectal cancer-specific survival (p for non-linear < 0.05). However, PAr was not significantly associated with either overall survival (HR_{Q4 vs. Q1}, 1.03; 95% CI: 0.75, 1.41) or colorectal cancer-specific survival (HR_{Q4 vs. Q1}, 1.01; 95% CI: 0.72, 1.42). The association between serum PLP and both overall survival and colorectal cancer-specific survival (p for interaction < 0.05) varied by alcohol drinking status. Conclusions: Higher serum PLP levels, but not PAr, may be associated with improved overall and colorectal cancer-specific survival. Full article