Search Results (644)

Background: Age-related differences in neuromuscular coordination during multi-joint tasks are reported, but phase-specific evidence during maximal sprinting is limited. Aim: The aim of this study was to investigate phase-specific age differences in agonist–antagonist coordination of the biarticular thigh muscles during 50 m sprinting. Methods: Thirty-eight healthy trained track athletes (Adults: n = 21, age = 23.32 ± 2.98 years; Adolescents: n = 17, age = 13.65 ± 0.76 years) performed maximal 50 m sprints over force plates. Bilateral rectus femoris (RF) and biceps femoris (BF) sEMG and ground reaction forces were recorded; each stride was segmented into seven phases, and an RF–BF co-contraction index (CCI) was calculated per phase. Between-group differences in phase mean CCI were tested (α = 0.05) and quantified with Hedges’ g. Speed- and frequency-dependent modulation of CCI was evaluated using linear mixed-effects models (LME; random intercepts for participant) with Frequency × Group and Speed × Group interaction terms; ordinary least squares (OLS) fits on stride cycle-level group means were descriptive. Linear and single-breakpoint segmented models were compared using the corrected Akaike information criterion (AICc) and Akaike weights. Results: Adolescents showed higher CCI in contact (right: Adults 0.09 ± 0.05 vs. Adolescents 0.13 ± 0.07, g = 0.68; left: Adults 0.08 ± 0.04 vs. Adolescents 0.12 ± 0.06, g = 0.84) and propulsive phases (right: Adults 0.08 ± 0.05 vs. Adolescents 0.13 ± 0.08, g = 0.68; left: Adults 0.07 ± 0.04 vs. Adolescents 0.12 ± 0.07, g = 0.84; p < 0.05 for both legs in both phases). LME identified Frequency × Group interactions in the stride cycle (ΔSlope = 0.10, p < 0.001) and late swing (ΔSlope = 0.12, p < 0.05) and a Speed × Group interaction in mid swing (ΔSlope = 0.01, p < 0.05). Mid swing showed a positive CCI–speed/frequency relationship in both groups, whereas across most other phases Adults downregulated CCI as speed/frequency increased while Adolescents tended to increase CCI. Model selection supported phase-dependent single-breakpoint patterns, with breakpoints around 2.19–2.21 Hz and 6.11–9.51 m·s⁻¹ in Adults and around 2.11 Hz and 7.13–7.59 m·s⁻¹ in Adolescents. Conclusions: Maximal sprinting revealed phase-specific age differences in BF–RF co-contraction and its scaling with speed/frequency, which may help guide age-informed monitoring and training considerations in developing athletes. Full article

Aim: Rapid maxillary expansion (RME) is a widely used interceptive orthodontic procedure in pediatric patients that is often associated with discomfort and pain, particularly during the initial phase of treatment. The present study aims to analyze the intensity and temporal trend of pain perceived by pediatric patients undergoing rapid palatal expansion (RME) by evaluating the influence of factors such as age, sex, type of maxillary transverse deficit, palatal expander, and dental anchorage. Materials and Methods: A prospective observational study was conducted on 134 pediatric patients (mean age 8 years; range 6–14 years) diagnosed with transverse maxillary contraction. Patients were treated with tooth-borne Haas or Hyrax expanders. Pain perception was monitored daily using a specific questionnaire with answers based on the Wong–Baker FACES scale. Collected data were analyzed by using the ANOVA test (p < 0.05). Results: Pain was a common symptom, with greater intensity in the first days of treatment. The Hyrax expander was associated with significantly greater initial pain than the Haas one (p < 0.001). Tooth-borne expanders on the first permanent molars resulted in greater initial pain than anchorage on the second primary molars (p < 0.001). Patients with unilateral posterior crossbite and anterior crossbite reported higher average pain levels (p < 0.001). Age emerged as a significant modulator of pain (p < 0.001), while no significant differences were found based on sex (p = 0.287). Conclusions: Expander type, tooth-anchorage type, maxillary transverse contraction type, and patient age significantly influenced pain perception during pediatric RME. These results provided useful indications for the clinical management of the patient, for the choice of expander and anchorage type and for the timing of intervention. Full article

Global warming profoundly affects hydrological processes and regional aridity. However, the shifts in the arid–humid transition zone and its relationship to divergent surface and subsurface hydrological responses remain not fully understood. This study investigates the spatiotemporal aridity changes in China using hydroclimate datasets (1950–2022) and examines associated hydrological responses via remote sensing (RS) since the early 2000s. The results reveal that: (1) a pronounced ~32-year oscillatory pattern governs both the expansion and contraction of drylands and non-drylands, with China currently in a wetting phase; (2) a distinct climatic transitional zone is identified, and a distinct boundary emerges separating drylands and non-drylands, here referred to as China’s Arid–Humid Divide, reflecting the climatic equilibrium shaped by multiple monsoon systems and local topography; and (3) the nationwide expansion of surface water bodies, following the increase of groundwater storage in partial areas, was detected via recent RS data. These findings provide new insights into the mechanisms driving long-term aridity transitions and support climate adaptation and sustainable land management in China. Full article

Construction disputes remain a major barrier to project success, particularly in international contexts characterized by diverse stakeholder expectations and high uncertainty. Although numerous studies have examined dispute causes, existing research is frequently limited by regional focus, phase-specific analysis, or delivery-method constraints. This study addresses these limitations by developing a lifecycle-based understanding of dispute causation through a semi-automated systematic literature review. A total of 6603 records were retrieved from Scopus and Web of Science, and after applying PRISMA-aligned screening and citation tracking, 52 peer-reviewed articles published between 2000 and 2024 were included. Bibliometric analysis was used to map publication trends, geographic distribution, journal contribution, and keyword networks, while content analysis supported the identification and consolidation of dispute causes across lifecycle phases. The results show that early project stages are dominated by unfair risk allocation, ambiguous contract documents, design errors, and unclear technical specifications, whereas the Execution phase is driven by variation orders, payment delays, ineffective communication, and unforeseen site conditions. Disputes in the Close-out phase remain underexplored, indicating a clear research gap. By linking dispute causes to specific lifecycle stages, the study provides a structured foundation for proactive dispute-prevention strategies and supports more effective management of construction projects worldwide. Full article

Studies examining the electromyographic activation of pectoralis major (PM) and triceps brachii (TB) muscles during push-ups of varied hand positions are limited, and findings are inconsistent. The aim was to investigate the electromyographic activation of PM and TB during standard, diamond, and wide hand position push-ups. Twenty young males performed six repetitions of each push-up variation while the electrical activity of PM and TB was recorded, averaged, and normalized to the peak root mean square (RMS) across repetitions for each push-up. RMS (mV) and normalized RMS (%) were calculated for each muscle, push-up variation, and contraction phase (eccentric/concentric). Two separate three-way ANOVAs with Bonferroni post hoc correction were used (α = 0.05). TB demonstrated statistically significantly higher RMS (mV) and normalized RMS (%) than PM (p < 0.05), in diamond, followed by standard and wide push-ups. A statistically significant higher activation of RMS (mV) was observed in concentric compared to eccentric (p < 0.05); however, after normalizing RMS (%), contraction phase had no effect (p > 0.05) and there was no significant three-way interaction (p > 0.05). Diamond push-ups elicited the highest relative activation for both the PM and TB. Normalized RMS revealed the consistency of muscle effort in both contraction phases, sustaining near-maximal activation regardless of hand position. These findings support adaptable training strategies, with potential applications in rehabilitation and strength training contexts. Full article

Accurately characterizing spatiotemporal patterns of carbon emissions and their driving mechanisms is essential for advancing regional low-carbon transitions. Focusing on northeast China, a representative old industrial base, this study develops a spatialized carbon emission estimation framework using an XGBoost model that integrates nighttime light data, land-use information, population, and economic indicators. A 1 km resolution carbon emission dataset spanning 2000 to 2021 is generated, and the SHAP method reveals nonlinear responses and stage-dependent evolutions of key driving factors. The results demonstrate three key findings. Carbon emissions in northeast China increased from 636 Mt in 2000 to 1131 Mt in 2021, exhibiting three distinct phases: rapid expansion (2000–2010, +36%), peak stabilization (2010–2015, +13%), and localized contraction (2015–2021, +3%). Liaoning Province contributed 46% of total emissions in 2021, while Jilin showed the fastest growth rate at 92%. County-level Moran’s I values (0.292–0.349) remain substantially lower than city-level values (0.642–0.700), revealing scale-dependent spatial clustering. High–high clusters concentrated persistently in southern Liaoning, encompassing eight cities by 2010, whereas low–low clusters dominated northern Heilongjiang. Population and GDP exhibited saturating marginal effects after 2015, with SHAP values plateauing beyond thresholds of approximately 450,000 persons and 420 billion CNY respectively, indicating gradual decoupling between economic growth and emissions. Industrial mining land influence declined by 68% from 2005 to 2020, while urban land-use ratio maintained stable contributions. This high-resolution spatiotemporal dataset provides empirical evidence for designing threshold-based emission reduction policies, identifying regional transfer risks, and implementing county-level differentiated strategies in old industrial bases undergoing low-carbon transition. The XGBoost–SHAP framework demonstrates transferability to other heavy industrial regions facing similar structural transformation challenges. Full article

This study investigates the pyrolysis behavior of loblolly pine through thermogravimetric (TGA) and derivative thermogravimetric (DTG) analysis under varying nitrogen flow rates of 5–40 mL min⁻¹ and heating rates of 5–20 °C min⁻¹. The pyrolysis proceeded through three distinct phases: Phase I: initial moisture release, Phase II: active devolatilization, and Phase III: char formation. Kinetic modeling using both integral and differential forms of the Coats–Redfern method revealed distinct mechanistic interpretations. The integral approach primarily identified diffusion-controlled models (D1, D3) during moisture and char stages and reaction-order or contraction models (F2, R2) during devolatilization, with activation energies ranging from 8.89 to 70.48 kJ mol⁻¹. In contrast, the differential method captured sharper transitions and favored complex nucleation and growth mechanisms (A3, A4) and power laws (P3, P4), yielding higher activation energies up to 111.29 kJ mol⁻¹ in Phase II. These results underscore the influence of both inert gas flow and thermal ramp on pyrolysis reactivity and demonstrate that kinetic model selection significantly affects activation energy interpretation. The findings contribute to a more nuanced understanding of biomass pyrolysis and offer insights into reactor design and process optimization in thermochemical conversion systems. Full article

The growing demand for marine resource development and in-depth exploration of the marine environment has positioned soft biomimetic underwater vehicles (SBUVs) as a research hotspot in the fields of underwater equipment and soft robotics. SBUVs are characterized by bodies made of flexible and extensible materials, integrating the dual advantages of softness and biomimetics. They can achieve muscle-like continuous deformation to efficiently absorb collision energy, while mimicking the propulsion mechanisms of marine organisms—such as fish and jellyfish—through undulating body movements or cavity contraction and relaxation. Such biomimetic propulsion is highly compatible with the flexible actuation of soft materials, enabling excellent environmental adaptability while maintaining favorable propulsion efficiency. Compared with traditional rigid underwater vehicles, SBUVs offer higher degrees of freedom, superior environmental adaptability, enhanced impact resistance and greater motion flexibility. This review systematically summarizes typical actuation methods for SBUVs—including fluid-powered actuation, shape memory alloy actuation, and electroactive polymer actuation—elaborating on their working principles, key technological advances, and representative application cases on SBUVs. These actuation mechanisms each offer distinct advantages. Fluid-powered systems are valued for high power density and precise motion control through direct fluidic force transmission. Shape memory alloys provide high force output and accurate positional recovery via controlled thermal phase changes. Meanwhile, electroactive polymers stand out for their rapid (often millisecond-scale) dynamic response, low hysteresis, and fine, muscle-like deformation under electrical stimuli. Current challenges are also analyzed, such as limited actuation efficiency, material durability issues, and system integration difficulties. Despite these constraints, SBUVs show broad application prospects in marine resource exploration, ecological monitoring, and underwater engineering operations. Future research should prioritize the development of novel materials, coordinated optimization of actuation and control systems, and breakthroughs in core technologies to accelerate the practical implementation and industrialization of SBUVs. Full article

Biological muscles generate tension from the combined contribution of the passive elastic recoil and the actively controlled contractile mechanisms. Understanding and replicating these passive and active tensions is necessary and beneficial for designing soft robotic actuators that emulate muscle-like behavior. In the current work, the aim is to develop a mathematical framework for modeling both the passive and active tensions in a biological muscle as functions of muscle length and contraction velocity. We will describe the passive tension by a nonlinear monotonically increasing function of length with threshold behavior in order to capture the experimentally observed stiffening occurring in stretched biological muscles. We will model the active tension using the superposition of Gaussian functions that relate bell-shaped tension-length with a flat plateau over the optimal length of the sarcomere. The parameters of this Gaussian representation of the active tension-length relation are determined from formulating a least-squares optimization problem, such that a Characteristic (indicator) function is approximated globally over the optimal length range of the sarcomere by summation of some Gaussian functions. The closed-form formulations for the required integrals are derived using the integral of the product of two Gaussian functions over ${\mathbb{R}}^n$ as well as the error function which enables efficient parameter identification. We will also propose a symmetric tension–velocity relation that distinguishes three phases of concentric, eccentric and isometric contractions, and is parametrized directly by measurable quantities of isometric tension and maximum shortening velocity. The passive and active tensions are finally combined into a unified comprehensive tension model in which the exponentially modeled passive tension is added up to the active contribution, formulated as the product of the activation level, a normalized length-dependent factor and a normalized velocity-dependent factor. The resulting model reproduces canonical tension-length and tension-velocity relations and provides an analytically tractable comprehensive tension model that can be embedded in the dynamics of soft and continuum robot actuators inspired by biological muscles. Full article

Background/Objectives: The calf muscles are vital for generating propulsive force during walking. This power is produced from calf muscle contractions and elastic strain energy release. However, the impact of walking speed on these power-generation mechanisms is understudied. This study aimed to investigate how different walking speeds affect calf muscle activation and ankle power generation. Methods: In this study, we analyzed electromyography (EMG) signals from the gastrocnemius (GAS) and soleus (SOL) muscles of 55 healthy individuals walking at various speeds. C1: household ambulators (0–0.4 m·s⁻¹), C2: limited community ambulators (0.4–0.8 m·s⁻¹), C3: community ambulators (0.8–1.2 m·s⁻¹), C4: self-selected usual speed, and C5: self-selected fast speed. Results: Deviating from a participant’s self-chosen pace led to increased cumulative muscle activity and prolonged plantar flexor activation. Optimal muscle activation was observed at speeds between 0.8–1.2 m·s⁻¹. A second-degree polynomial mixed model best captured the relationship between muscle activation duration and integrated EMG in the ankle power generation phase in late stance, demonstrating the nonlinear relationship between walking speed and calf muscle activation in this phase. Statistically significant models (p < 0.001) explained over 50% of the variability in GAS activation duration (R² = 0.55) and integrated EMG (R² = 0.56), as well as SOL activation duration (R² = 0.52) and integrated EMG (R² = 0.72). Conclusions: The nonlinear relationship between walking speed and calf muscle activation indicates that normal walking speed optimizes the utilization of elastic strain energy in the ankle power generation phase. Full article

This study investigates the dynamics of electricity consumption in Brazil over the past two decades, with a focus on the persistent slowdown in consumption growth observed since 2013. Using segmented regression and interrupted time series (ITS) modeling, the research identifies statistically significant structural breakpoints in national and regional electricity demand. The main novelty of this study lies in the integrated use of segmented regression, ITS, and seasonal SARIMA models to systematically characterize asymmetric and phase-dependent demand behavior rather than to produce short-term forecasts. Seasonal Autoregressive Integrated Moving Average (SARIMA) models reveal that monthly seasonality plays a dominant role in electricity consumption dynamics, with seasonal specifications consistently outperforming non-seasonal alternatives. The results show that Brazil’s electricity demand evolution is best explained by three distinct phases: (i) a stagnation of industrial demand associated with deindustrialization prior to 2013; (ii) an abrupt contraction in commercial and residential demand during the 2014–2016 economic crisis; and (iii) a permanently lower growth trajectory driven by energy efficiency policies under the Brazilian National Electric Energy Conservation Program (PROCEL) and the expansion of solar distributed generation. The findings demonstrate that policy and structural interventions exert gradual, cumulative effects on electricity consumption rather than immediate shifts, providing critical insights for long-term energy planning and policy design in emerging economies. Full article

The widespread adoption of electricity market trading platforms has enhanced the standardization and transparency of trading processes. As markets become more liberalized, regulatory policies are phasing out protective electricity pricing mechanisms, leaving retailers exposed to price volatility risks. In response, demand for risk management tools has grown significantly. Futures contracts serve as a core instrument for managing risks in the energy sector. This paper proposes a futures-based risk hedging model grounded in electricity price forecasting. A price prediction model is constructed using historical data from electricity markets and energy futures, with SHAP values used to analyze the transmission effects of energy futures prices on monthly electricity trading prices. The Monte Carlo simulation method, combined with a t-GARCH model, is applied to calculate CVaR and determine optimal portfolio weights for futures products. This approach captures the volatility clustering and fat-tailed characteristics typical of energy futures returns. To validate the model’s effectiveness, an empirical analysis is conducted using actual market data. By forecasting electricity price trends and formulating futures strategies, the study evaluates the hedging and profitability performance of futures trading under different market conditions. Results show that the proposed model effectively mitigates risks in volatile market environments. Full article

Freeze-thaw (F-T) cycles in seasonally frozen regions induce progressive volumetric strains leading to degradation of soils’ mechanical properties and performance of earthen infrastructure. Conventional chemical stabilization techniques often are not adaptive to cyclic thermal stresses and do not address the fundamental phase changes of porous media, underscoring the need for sustainable alternatives. This study explores the potential of extracellular polymeric substances (EPS) produced by the psychrophilic bacterium Polaromonas hydrogenivorans as a bio-mediated soil treatment to enhance freeze-thaw durability. Two EPS formulations were examined—EPS 1 (high ice-binding activity) and EPS 2 (low ice-binding activity)—to evaluate their effectiveness in improving volumetric stability and thawing strength of silty soil subjected to ten F-T cycles. Tests were conducted at four moisture contents (12%, 18%, 24%, and 30%) and three EPS concentrations (3, 10, and 20 g/L). Volumetric strain measurements quantified freezing expansion and thawing contraction, while unconfined compressive strength assessed post-thaw mechanical integrity. The untreated soils exhibited maximum net volumetric strains (γ_Net) of 5.62% and only marginal strength recovery after ten F-T cycles. In contrast, EPS 1 at 20 g/L mitigated volumetric changes across all moisture contents and increased compressive strength to 191.2 kPa. EPS 2 yielded moderate improvements, reducing γ_Net to 0.98% and enhancing strength to 183.9 kPa at 30% moisture. Lower EPS concentrations (3 and 10 g/L) partially mitigated volumetric strain, with performance strongly dependent on moisture content. These results demonstrate that psychrophilic EPS, particularly EPS 1, effectively suppresses ice formation within soil pores and preserves mechanical structure, offering a sustainable, high-performance solution for stabilizing frost-susceptible soils in cold-regions. Full article

Road infrastructure underpins Nigeria’s economic competitiveness, yet Public–Private Partnership (PPP) performance is constrained not by inadequate legislation but by persistent weaknesses in enforcement and governance. Transparency deficits across procurement, design management, certification, and toll-revenue reporting have produced chronic delays, cost overruns, and declining public trust. This study offers the first empirical investigation of blockchain–Building Information Modelling (BIM) integration as a transparency-enhancing mechanism within Nigeria’s PPP road sector, focusing on Lagos State. Using a qualitative design, ten semi-structured interviews with stakeholders across the PPP lifecycle were thematically analysed to diagnose systemic governance weaknesses and assess the contextual feasibility of digital innovations. Findings reveal entrenched opacity rooted in weak enforcement, discretionary decision-making, and informal communication practices—including biased bidder evaluations, undocumented design alterations, manipulated certifications, and toll-revenue inconsistencies. While respondents recognised BIM’s potential to centralise project information and blockchain’s capacity for immutable records and smart-contract automation, they consistently emphasised that technological benefits cannot be realised absent credible institutional foundations. The study advances an original theoretical contribution: the Codify–Condition–Capacitate framework, which explains the institutional preconditions under which digital governance tools can improve transparency. This framework argues that effectiveness depends on: codifying digital standards and legal recognition; conditioning enforcement mechanisms to reduce discretionary authority; and capacitating institutions through targeted training and phased pilots. The research generates significant practical implications for policymakers in Nigeria and comparable developing contexts seeking institution-aligned digital transformation. Methodological rigour was ensured through purposive sampling, thematic saturation assessment, and documented analytical trails. Full article

Background/Objectives: Magnetic resonance imaging (MRI) can be used to assess muscle function while performing a motion task within the scanner. Quantitative measures such as contraction velocity and strain can be derived from the images. Cine phase contrast (PC) MRI for time-resolved imaging of muscle function relies on the consistently repeated execution of the motion task for several minutes until data acquisition is complete. This may be difficult for patients with neuromuscular dysfunctions. To date, this approach has been applied only in adults, but not pediatric populations. The aim of this pilot study was to investigate the feasibility of PC MRI for assessing calf muscle function during electrically evoked and voluntary motion in children with cerebral palsy (CP) using open-source hardware and software. Methods: Cine PC MRI was performed at 3T in ambulatory pediatric patients with CP and typically developing children under electrical muscle stimulation (EMS) (n = 14/13) and during voluntary plantarflexion (n = 4/4) using a home-built pedal with a force sensor. A visual feedback software was developed to enable synchronized imaging of voluntary muscle contractions. Muscle contraction velocity and strain were calculated from the MRI data. Data quality was rated by two readers. Results: During EMS, the velocity data quality was rated as sufficient in 21% of scans in patients compared with 82% of scans in controls. During the voluntary task, all patients demonstrated increased compliance and greater generated force output than during EMS. Voluntary motion imaging was successful in all controls but none of the patients, as motion periodicity in patients was worse during voluntary than during stimulated contraction. Conclusions: Cine phase-contrast MRI combined with EMS or voluntary motion proved challenging in pediatric patients with CP, particularly in those with more severe baseline muscle dysfunction or reduced tolerance to stimulation. In contrast, the approach was successfully implemented in typically developing children. Although the scope of the patient-based findings is limited by data heterogeneity, the method demonstrates considerable potential as a tool for monitoring treatment-related changes in muscle function, particularly in less severely affected patients. Further refinement of the EMS and voluntary motion protocols, together with a reduction in MRI acquisition time, is required to improve motion periodicity, tolerability, and consequently the overall success rate in the intended pediatric patient cohort. Full article