Search Results (2,436)

The retrofitting of existing stadiums with retractable roof systems presents a complex interdisciplinary challenge, requiring the reconciliation of aged structural capacity with modern performance demands. This paper investigates the engineering design and analysis of a new retractable roof system for the Ningbo (Yinzhou) Tennis Center, a facility originally completed in 2007 and now requiring an upgrade to host higher-tier WTA 500 events. The retrofit is further complicated by increased seismic design requirements and the need to preserve the existing structure. To address these constraints, this study proposes a novel, structurally independent roof system comprising 12 radially deployable units supported by an external single-layer spatial grid and lambda-shaped columns. A multidisciplinary approach integrates structural engineering, mechanical systems, and architectural technology. Key innovations include (1) the selection and detailed modeling of a rack-and-pinion drive mechanism, with a floating engagement design to accommodate dynamic load transfer; (2) a two-stage analytical framework employing both sub-assembly and integrated assembly finite element models to capture the unique mechanical behavior and coupling effects between the new and existing structures; (3) the strategic implementation of circumferential hoop cables to counteract uplift forces and redirect the internal force distribution in the supporting bifurcated columns; and (4) the validation of structural integrity through comprehensive static, stability, and seismic gap analyses, informed by wind tunnel testing. The results demonstrate that the proposed system satisfies all strength, stiffness, and stability criteria under multiple operational states (open, closed, and transitional) and meets the enhanced seismic fortification standards. This research provides a validated theoretical foundation and practical implementation guidelines for this specific stadium retrofit, demonstrating a viable pathway for extending the service life of aging sports infrastructure, with insights that may inform similar urban renewal projects under comparable conditions. Full article

The Aedes aegypti mosquito exhibits a critical behavioral adaptation through its oviposition strategy, laying eggs in dry and wet environments just above the water level, allowing eggs to resist desiccation and hatch only when submerged by rain. To investigate this mechanism, we developed a nonlinear dynamic model incorporating climate-driven parameters affecting egg hatching and adult emergence. Theoretical analysis revealed an imperfect pitchfork bifurcation giving rise to a phenomenon we term basin-mediated hysteresis. Unlike classical hysteresis, which relies on coexisting stable states, this mechanism results from the progressive collapse of the extinction basin boundary. As the control parameter approaches its critical value, the basin of attraction of the trivial equilibrium shrinks. Once the population establishes itself above the threshold, returning the parameter below unity does not restore extinction, leading to an irreversible transition governing population persistence. The model was validated using field data from mosquito traps in a Brazilian city, showing strong agreement with observed seasonal patterns of female captures. Parameters were optimized using the Differential Evolution algorithm, yielding high correlation between model and field data. The results demonstrate that the dual oviposition strategy underlies population persistence and seasonal peaks, providing information for planning interventions amid global arbovirus expansion. Full article

In deep geothermal engineering, concrete slabs are prone to thermal cracking. The aggregates and pores are the core influencing factors for this failure behavior. However, existing research methods are unable to accurately capture the microscopic evolution process of thermal cracking and cannot clarify the intrinsic mechanism of how the characteristics of aggregates and pores affect the initiation and propagation of cracks. This limitation restricts the in-depth understanding of the laws of concrete thermal cracking. To address this deficiency, this study employs the discrete element method (DEM) and combines the particle flow program PFC2D to construct a microscopic model of concrete disks. By setting reasonable temperature parameters and thermal load boundaries, a numerical simulation system matching the actual deep geothermal high-temperature environment is established. Three sets of quantitative variables were designed: aggregate particle size (0.003, 0.004, 0.005, 0.006), aggregate volume fraction (0.35, 0.40, 0.45, 0.50), and porosity (0.11, 0.12, 0.13, 0.14). Through controlled variable simulations, the influence laws of each variable on the formation, propagation path, and time evolution of concrete thermal cracks were explored. The quantitative research results show that an increase in aggregate particle size significantly accelerates the generation and propagation of cracks. When the particle size is 0.006, the number of cracks is the highest and the propagation rate is the fastest. The aggregate volume fraction is negatively correlated with the final number of cracks, and 0.50 is the optimal fraction, at which the number of cracks is the smallest. A decrease in the fraction will lead to intensified stress concentration in the cement paste and a sudden increase in the number of cracks. An increase in porosity significantly disrupts the material continuity. When the porosity is 0.14, the bifurcation and connection of cracks are the most significant, while a low porosity of 0.11 can effectively inhibit the overall development process of thermal cracks. In addition, compared with traditional experimental methods and continuous medium numerical simulation techniques, the discrete element method has unique advantages in revealing the internal mechanism of concrete thermal cracking at the microscopic level. It can achieve real-time tracking of the evolution of discrete micro-cracks and the internal stress distribution characteristics. This study enriches the microscopic theoretical system of concrete thermal cracking and provides reliable quantitative references and technical support for the design of thermal crack resistance of concrete in deep geothermal engineering and the optimization of material composition. Full article

A study was conducted to evaluate the effect of neutral detergent fiber (NDF) levels of calf starter and weaning time on growth, rumen fermentation characteristics, serum metabolites, and rumen microbial diversity of Holstein calves. A total of 24 newly born male Holstein calves were randomly distributed to four groups in a completely randomized design with a 2 × 2 factorial arrangement of NDF levels (14% and 24%) and weaning time (d 44 and d 54). There was no interaction between starter NDF levels and weaning time for any trait except rumen acetic acid in the immediate post-weaning phase (p = 0.013). Starter NDF levels had no effect on growth, feed intake, and hay intake. Late-weaned calves had greater (p = 0.050) weight gain in the pre-weaning phase whereas, early-weaned calves showed greater weight gain (p = 0.004) and starter intake (p = 0.004) in the post-weaning phase although overall weight gain, and starter and hay intakes were not affected by weaning time. Rumen pH, ammonia nitrogen, and most volatile fatty acids remained unaffected by starter NDF levels and weaning except isobutyric acid which was greater in calves fed 24% NDF starter (p = 0.001) in the immediate post-weaning and isovaleric acid which was greater in early-weaned calves (p = 0.044) at the end of experiment. Serum metabolites were largely affected (p < 0.05) by starter NDF levels and weaning time in the pre-weaning phase only. Alpha diversity of rumen microbes was greater and chaotic in 14% NDF starter group (early- and late-weaned) in the pre-weaning phase which converged in the immediate post-weaning phase and diverged on starter NDF basis at the end of experiment. Microbial ecology at phylum and genus levels composition were greatly driven by starter NDF levels in the pre-weaning phase, by weaning time in the immediate post-weaning phase, and two distinct bifurcated microbial ecologies based on starter NDF levels appeared at the end of experiment. In conclusion, the comparable growth with distinct microbial diversity but largely in favor of 24% NDF starter suggests that calves can be subjected to early weaning with 24% starter NDF levels for smooth transition from liquid to solid feed in Holstein calves. Full article

Traditional analyses of transport phenomena rely on prescribed geometric boundaries, yet natural flow systems dynamically evolve their architecture to maximize access to currents. To address this disparity, we propose a field-theoretic framework for the constructal law that treats physical geometry as a dynamic state variable, represented by a time-dependent conductivity tensor. Using a variational approach grounded in non-equilibrium thermodynamics, we derive a general tensor evolution equation. Within this framework, macroscopic flow architecture emerges deterministically from the continuous competition between non-linear flux-induced accretion, linear entropic relaxation, and spatial smoothing. Scaling analysis reduces this dynamic to a tri-parameter dimensionless phase space: a morphogenic number driving structural growth, a structural diffusion number governing spatial coherence, and a stochastic intensity number providing the microscopic seeds for symmetry breaking. Our principal result is the analytical prediction of a critical bifurcation. When the local morphogenic number strictly exceeds unity, the system escapes its stable, isotropic configuration and branches into highly conductive, anisotropic architectures. We demonstrate the predictive validity and trans-scalar applicability of this continuum theory by mapping it to highly diverse phase transitions, successfully capturing phenomena ranging from microscopic aerosol agglomeration and microbial resistance, to macroscopic coral plasticity and crystal growth instabilities, and finally to the astrophysical launching of relativistic jets from black holes. Full article

In this work, we present a numerical proof-of-concept study of a device for nanoparticle sorting, targeting size ranges relevant to exosome-like dimensions (typically 40–200 nm), which remains challenging for passive sorting techniques. The system consists of three silicon waveguides embedded in a CYTOP layer and arranged in a two-step directional-coupler configuration, integrated with a microchannel that carries a water-based buffer as the carrier fluid, transporting the suspended nanoparticles. Three-dimensional Finite Element Method (3D-FEM) simulations were performed, incorporating both optical and hydrodynamic forces to track particle dynamics within the microchannel and demonstrate controlled, size-selective particle deflection. First, numerical simulations show that nanospheres with diameters ranging from 500 nm to 700 nm can be effectively separated by the transverse trapping force at a 4:1 power-splitting ratio. Then, to extend the concept toward smaller size ranges, a bifurcated microchannel is introduced, enabling fluid-assisted transport in low-optical-field regions and allowing reliable separation of particles with smaller diameters (between 200 nm and 400 nm), accompanied by an 8:1 power-splitting ratio. These results demonstrate, within a numerical framework, the feasibility of an integrated photonic–microfluidic approach for size-selective nanoparticle sorting. The proposed strategy may support future pre-processing steps in liquid biopsy workflows, particularly for enriching nanoscale components such as exosome-sized vesicles, rather than constituting a direct diagnostic tool. Full article

This study proposes a novel image encryption algorithm based on a two-dimensional discrete chaotic system that integrates cellular automata (CA) with a tent map. The algorithm addresses security vulnerabilities in digital image transmission and storage across open networks or cloud environments. It employs a three-phase encryption process: coordinate permutation, spatial permutation, and diffusion. Sequential application of Arnold’s coordinate scrambling, maze traversal-based spatial rearrangement, and a CA-driven diffusion mechanism enhances robustness against noise, differential attacks, and partial cropping. A Dynamic CA–Tent Map (DCA–TM) hybrid chaotic system is designed to overcome periodicity and limited key space issues inherent in conventional chaotic encryption. The permutation stage is refined into coordinate and spatial phases to achieve comprehensive pixel randomization. During diffusion, CA rules are selected dynamically based on the iteration counts of the initial parameters, yielding an adaptive encryption system with a variable key space. Performance evaluations—including Lyapunov exponent tests, bifurcation analysis, information entropy measurement, and pixel correlation assessment—confirm the strong chaotic behavior and high security of the proposed scheme. Full article

Transcriptional and translational inhibition are fundamental regulatory mechanisms in gene networks, governing diverse processes from viral replication to neuroplasticity. Two-component genetic oscillators based on the “activator–repressor” motif serve as ideal models for studying biological rhythms due to their simplicity and rich dynamics. However, systematic theoretical comparisons of distinct inhibitory mechanisms—particularly using inhibition strength as a control variable—remain lacking. Addressing this gap, we present a comprehensive bifurcation analysis of the post-translational repression model, proving the existence and uniqueness of its positive equilibrium, deriving Hopf bifurcation conditions, and identifying critical parameter ranges for sustained oscillations. Using inhibition strength as a key comparator, we systematically contrast transcriptional and post-translational repression, elucidating how different inhibitory mechanisms modulate oscillation initiation and amplitude. We further reveal distinct symmetry–asymmetry patterns in their bifurcation dynamics: transcriptional repression exhibits asymmetric bistable regimes, while post-translational repression manifests narrow, nearly symmetric oscillatory intervals. This unified analytical framework not only advances the theoretical understanding of two-component genetic oscillators but also provides a generalizable paradigm for dissecting complex gene regulatory dynamics. Full article

Alzheimer’s disease (AD) develops as a progressive dementia condition through the step-by-step breakdown of nerve cells. Neurodegeneration in this context primarily results from metal ions, including copper, iron, zinc, and aluminum, building up in the system. The aggregation of amyloid-beta (Aβ) peptides and oxidative stress generation stem from metal ion involvement acting as defining characteristics of Alzheimer’s disease pathology. We developed a comprehensive mathematical model based on 24 coupled ordinary differential equations (ODEs) to represent the interactions between metal ions, Aβ peptides, reactive oxygen species (ROS), antioxidant defenses, and tau protein phosphorylation. The mathematical model monitors how metal ion concentrations change over time and examines their competitive binding effects, which trigger a series of reactions, resulting in oxidative stress and subsequent tau protein damage. The model uses analytical and numerical mathematical methods to expose nonlinear behaviors and threshold effects while offering mechanistic insights into the course of disease development. This model functions as a quantitative framework for assessing how therapeutic interventions that target metal dyshomeostasis and oxidative stress can potentially affect outcomes. Full article

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) coupled with methanol reforming hold promise for distributed energy systems, yet channel hydrodynamics and geometry optimization remain underexplored. This study develops a 3D multiphysics model to investigate coupled behaviors in HT-PEMFCs fueled by methanol reformate. Results reveal bifurcation-induced Dean vortices have dual effects: they cause flow maldistribution (15–18% velocity deviation) and contribute 50% of inlet pressure loss, while generating a lateral pumping effect that enhances local mass transfer. A continuous parametric sweep of channel widths (0.9–1.9 mm) identifies a voltage-dependent performance crossover—narrower channels (1.3 mm) excel at high voltages by improving electronic conduction, whereas wider channels (1.5 mm) perform better at low voltages by mitigating mass transfer limitations. These findings provide quantitative design criteria for optimizing flow field geometry in HT-PEMFC stacks. Full article

In this paper, based on the Caputo-like delta fractional difference operator, we will present a fractional discrete model of a 4D Power System. We present an extension of the popular integer-order single-machine infinite-bus formulation to two fractional cases, one with commensurate (equal) fractional orders and another incommensurate (not equal). This extension captures long-memory effects in dynamics and thus offers a consistent mathematical description of the nonlinear behavior of power systems. The orders of the fractional models are analyzed numerically. Using time series evolution, phase-space plots, bifurcation maps, Lyapunov spectra, and the 0–1 chaos test, spectral entropy and $C_0$ complexity metrics, we identify chaotic regimes. Additionally, techniques for controlling chaos are explored to stabilize and regulate the dynamics of the system. Both the fractional formulations exhibit richer dynamical features than their integer counterparts, and for the incommensurate case, the sensitivity to the fractional variations is larger, generating complex nonlinear oscillations. The fractional discrete power system framework provides a new perspective for studying instability, the voltage collapse phenomenon, and chaotic oscillations in power engineering applications. Full article

In flexible manufacturing systems, the composite mobile manipulator (CMM) is subject to nonlinear inertial disturbances arising from the dynamic coupling between the mobile platform and the robotic arm. These disturbances significantly impair positioning precision during grasping tasks. This paper addresses the dynamic decoupling of multi-body nonlinear inertial disturbances within CMM systems. Departing from the conventional “stop-then-plan” serial execution paradigm, we propose a full-cycle spatiotemporally coupled trajectory optimization method. The operation cycle is bifurcated into two synergistic stages: “dynamic calibration” and “static execution.” The dynamic calibration trajectory is pre-planned and executed synchronously during platform movement to actively compensate for inertial-induced pose deviations. Concurrently, the static execution trajectory is optimized and then triggered immediately upon platform standstill, ensuring a seamless and precise transition to the “Grasping Pose”. It is worth noting that the temporal characteristic central to this framework lies in the concurrent execution of static trajectory optimization and platform transit: by the time the platform reaches its destination, the pre-planned trajectory is already available for immediate triggering, achieving zero task-switching wait time at the planning layer. The term “zero-latency” here does not imply a fixed-cycle real-time response at the control layer, but rather the complete elimination of decision latency afforded by the parallel planning architecture. This framework eliminates computational latency, markedly enhancing operational efficiency. Key innovations include two novel constraints. First, the Adaptive Task-space Bounded Search Constraint (ATBSC) framework restricts optimization to a geometry-inspired search region, thereby enhancing search efficiency and ensuring controllable deviations. Second, the Multi-Rigid-Body Coupling Constraint (MRBCC) system explicitly models inertial transmission across motion phases to suppress pose fluctuations. The proposed framework is developed and validated within an obstacle-free workspace. In simulation-based validation on a UR10 6 degree-of-freedom manipulator model, experimental results indicate that ATBSC increases valid solution density to 84.7% and reduces average deviation by 72.8%. Furthermore, under the tested conditions, MRBCC mitigates end-effector position errors by 79.7–81.0% with a 97.5% constraint satisfaction rate. The improved Cuckoo Search algorithm (ICSA), serving as the solver component of the proposed framework, achieves an 11.9% lower fitness value and a 13.1% faster convergence rate compared to the standard Cuckoo Search algorithm in the tested scenarios, suggesting its effectiveness as a reliable solver for the constrained multi-objective trajectory optimisation problem. Full article

Background/Objectives: Sarcopenia is a progressive skeletal muscle disorder linked to adverse outcomes. Computed Tomography (CT) can quantify skeletal muscle, while the Charlson Comorbidity Index (CCI) predicts mortality by categorising comorbidities. This study examined whether Computed Tomography of the Kidneys, Ureters, and Bladder (CT-KUB)-derived skeletal muscle measurements correlate with CCI scores in hospitalised patients. Methods: This retrospective study included all patients admitted with renal colic to the Urology Department, Blacktown Hospital and underwent cystoscopy between June 2022 and June 2025. Data were obtained from electronic medical records. CCI scores, incorporating age and comorbidities, generated 10-year survival estimates. CT-KUB scans were reviewed for psoas muscle perimeter, area, height, width and Hounsfield unit at the aortic bifurcation. Skeletal Muscle Index (SMI) was calculated as skeletal muscle area (SMA)/height². Associations between CCI, psoas muscle metrics and outcomes (length of stay, Intensive Care Unit (ICU) admission, Emergency Department (ED) re-presentation) were assessed using Pearson’s correlations and between-group comparisons. Results: A total of 397 patients were analysed. Median Length of Stay (LOS) was 1 day (mean = 1.92, SD = 1.88). ICU admission occurred in 2.3% of patients, and 18.6% re-presented to ED within 30 days. Both CCI survival percentage and psoas muscle metrics (including SMI) were significantly associated with LOS. Lower SMA, Hounsfield unit (HU), length and perimeter were linked to higher ICU admission risk. Neither CCI nor muscle measures predicted ED re-presentation. Conclusions: CCI and CT-derived muscle metrics were independently associated with outcomes such as LOS and ICU admission. Combining these measures may improve risk stratification, warranting further prospective evaluation. Full article

In this paper, a supply–demand–price network model incorporating a marginal feedback mechanism is proposed to characterize the evolution of market prices. Unlike classical supply–demand models, the marginal effect of excess demand, defined as the rate of change in excess demand, is explicitly introduced into the price adjustment process. As the coefficient of the marginal feedback term varies, the system exhibits rich and complex nonlinear dynamics. In particular, the model gives rise to a centrally symmetric double-wing chaotic attractor, as well as a pair of coexisting single-wing chaotic attractors. The transition routes among different dynamical regimes are systematically analyzed using phase portraits, bifurcation diagrams, and Lyapunov exponents. Furthermore, multistability phenomena are observed, including the coexistence of equilibrium points, limit cycles, and chaotic attractors. The corresponding basins of attraction are illustrated to reveal their intricate and interwoven structures. In addition, the emergence of endogenous chaos is investigated through both theoretical analysis and numerical simulations. Finally, the consistency between the model dynamics and real market data provides empirical evidence supporting the validity and applicability of the proposed framework. Full article

In this paper, we investigate the multi-scale dynamics of a singularly perturbed Rosenzweig–MacArthur model with a generalist predator and identify dynamical phenomena, including equilibrium bifurcations, supercritical or subcritical singular Hopf bifurcations, canard explosion bifurcations and homoclinic bifurcations. Specifically, the system exhibits a globally stable node, a headless canard cycle evolving into a homoclinic cycle, a headed canard cycle encompassing either a headless canard cycle or a homoclinic cycle, and so on. Notably, near the boundary equilibrium, these cycles exhibit a diminutive beard-shaped structure whenever it aligns with the transcritical non-normally hyperbolic point. The numerical simulations confirm the occurrence of a canard explosion, relaxation oscillation, and an inverse canard explosion phenomena not previously reported in singularly perturbed systems with both a transcritical point and a canard point. In brief, our results demonstrate that the generalist predation can cause richer bifurcations and dynamics. Full article