External Load Research Articles

Kinematics-Based Predictions of External Loads during Handcycling.

The increased risk of cardiovascular disease in people with spinal cord injuries motivates work to identify exercise options that improve health outcomes without causing risk of musculoskeletal injury. Handcycling is an exercise mode that may be beneficial for wheelchair users, but further work is needed to establish appropriate guidelines and requires assessment of the external loads. The goal of this research was to predict the six-degree-of-freedom external loads during handcycling from data similar to those which can be measured from inertial measurement units (segment accelerations and velocities) using machine learning. Five neural network models and two ensemble models were compared against a statistical model. A temporal convolutional network (TCN) yielded the best predictions. Predictions of forces and moments in-plane with the crank were the most accurate (r = 0.95-0.97). The TCN model could predict external loads during activities of different intensities, making it viable for different exercise protocols. The ability to predict the loads associated with forward propulsion using wearable-type data enables the development of informed exercise guidelines.

Disentangling external loadings, hydrodynamics and biogeochemical controls on the fate of nitrate in a coastal embayment

Nitrogen, as an essential nutrient, largely contributes to the coastal eutrophication. However, the accurate depiction and evaluation of how external loadings, hydrodynamics, and biogeochemical reactions mediate the occurrence, transport, and transformation of nitrate (NO3-) within coastal embayment still pose ongoing challenges to date. In this study, we took advantage of dual isotopes of NO3- to track external NO3- loadings, radium and dual isotopes of H2O to characterize the influences of hydrodynamic on NO3- transport, δ18O-NO3- and δ18O-H2O along with microbial analysis to explore major NO3- biogeochemical reactions in Tolo Harbour, Hong Kong. The multiple isotopic evidence showed that NO3- in surface harbour water was predominantly contributed by precipitation in wet season and its impact was strengthened by stratification. In dry season, NO3- in the surface harbour water became largely influenced by benthic input and biogeochemical reactions due to intensified vertical mixing. Based on NO3- mass balance model, biogeochemical reaction, especially nitrification, was found to be the major process to secure the closure of NO3- budget and increase NO3- inventory from wet to dry season. Hydrodynamics redistributed the external NO3- loadings and mediated nitrogen biogeochemical reactions, both of which further synergistically regulated the fate of NO3- in the embayment.

FLEXIBILITY STUDY OF A PIPELINE SYSTEM IN FIBER-REINFORCED POLYMER

This study evaluates the flexibility of a fiber-reinforced polymer (FRP) pipeline system, focusing on its ability to withstand various loads and stresses while maintaining structural integrity. Key aspects include analyzing FRP material properties, assessing pipe geometry, evaluating external and internal loads, and performing a flexibility analysis using CAESAR II software. The initial findings indicated that the stress levels exceeded permissible limits, necessitating adjustments in support positions and types. These adjustments successfully reduced stress levels to acceptable thresholds, ensuring reliable system performance. This study highlights the importance of meticulous design and continuous optimization to guarantee the safety and durability of FRP pipeline installations.

Multi-scale FE analysis of coupled load-moisture mechanical behavior of saturated asphalt pavements considering transversely isotropic permeability

Assessing the collective impacts of external loading and void pressure on the mechanical behavior of porous media presents a significant challenge due to its inherent heterogeneity and complex multi-physical field coupling mechanisms. This study addresses this challenge by developing a novel multiscale hydraulic-mechanical modeling framework to investigate the structural response of water-saturated asphalt pavement under sequential coupling hydro-mechanical loading. The framework comprises three key components. Firstly, incorporating an upscaling homogenization approach to establish the linkage of material properties between different scales; secondly, developing a downscaling transfer procedure to transfer the structural response across scales for insight into its multiphysics mechanisms; and finally, proposing a new sequential coupling algorithm in multiscale simulations for comprehensive multi-field coupling calculations. The primary outcomes of this study demonstrate that asphalt concrete (AC)-graded pavements are susceptible to “down-top” cracks under hydro-mechanical loading, while open graded friction course (OGFC)-graded pavements have the potential to develop both “top-down” and “down-top” cracks. In AC-graded pavements, increasing the hydraulic head reduces stress concentrations, while in OGFC-graded pavements, changes in the permeability coefficient have a lesser impact on mechanical response. At the mesoscopic level, tensile stress concentrations in the asphalt mortar decrease significantly at higher temperatures. Furthermore, the OGFC-graded RVE model exhibits higher tensile stresses in the asphalt mortar compared to the AC-graded RVE model.

Long-term responses of internal environment dynamics in a freshwater lake to variations in external nutrient inputs: A model simulation approach

Lake restoration usually focuses on reducing external nutrient sources. However, when sediments contain nutrients accumulated over multiple years, internal nutrient release can delay restoration progress. In lake restoration and management, it is important to understand the dynamic relationship between nutrient concentrations in a lake and internal and external nutrient sources. In this study, we quantified external nutrient inputs through measurements and compared them with internal sediment release from simulation using the PCLake+ model. Additionally, we evaluated alterations in the internal nutrient release, lake nutrient concentrations, and algae biomass (chlorophyll-a) within the lake following varying degrees of reduction in external nutrient loads. The results demonstrate that the PCLake+ effectively simulated the lake's nutrient concentration and algae biomass. Based on the PCLake+ estimates, internal nutrient loads accounted for 51 % of the total nitrogen (N) and 80 % of the total phosphorus (P) loadings in Lake Erhai in 2019. In 2020, the total contributions were 43 % for TN and 72 % for TP. We simulated four scenarios where external nutrient inputs were reduced to 25 %, 50 %, 75 %, and 99.99 % of their original levels. The 40-year simulation showed that the lake's ecological system initially exhibited a fast internal response but reached equilibrium after eight years. P concentrations took longer to reach equilibrium compared to N concentrations, probably due to the stronger binding characteristics of P. To meet the water quality target in the future, it is necessary to reduce external N and P inputs into Lake Erhai by at least 23 % and 15 %, respectively, under current conditions. Although reducing external nutrient loads can indirectly lower internal nutrient loads, water management should address both external and internal loads simultaneously, as internal release cannot be effectively reduced by external reductions alone. Additionally, the lake's internal release may continue for several years, even with reductions in external inputs.

Multi-scale approach to hydrogen susceptibility based on pipe-forming deformation history

Hydrogen-induced-cracking initiates without external loading due to residual stresses. Pipe manufacturing process composed of crimping, U-ing, O-ing, and expansion has a major impact on local hydrogen concentration, as strain pattern evolves from one forming step to another, causing residual stresses that serve as driving force for hydrogen diffusion. The novelty of the presented work lies in the development of a multi-scale approach that links the residual stresses from the macroscopic pipe-forming process with locally dissolved hydrogen atoms in microstructure under the consideration of microstructural heterogeneities to identify areas susceptible to hydrogen-induced-cracking. First, a 3d-pipe-forming-model was built. Second, representative volume elements with lattice defects were generated to analyze hydrogen trapping in microstructure. Third, representative volume elements were placed in the pipe via sub-modeling, so that local loading history of the pipe was assigned to microstructure models. At the end of the pipe-forming process, representative volume elements were loaded with hydrogen on the surface and final hydrogen concentration was simulated based on residual stresses, considering microstructural effects such as grain size/shape, crystallographic texture and hydrogen traps, e.g. dislocations, voids and inclusions. On meso-/macroscale, a combined isotropic–kinematic hardening material model was implemented, while on microscale, a phenomenological crystal-plasticity-hydrogen-diffusion model was coded. According to the multi-scale simulations under the consideration of microstructural effects the bottom center position in the pipe was detected to be critical to hydrogen-induced-cracking as the maximum local hydrogen concentration was predicted at that location. Based on the loading history hydrogen-induced-cracking susceptibility increases from voids to hard and soft non-metallic inclusions.

Improving seismic performance for inclined historical building by using external protection structure: Case study of Yingxian wooden pagoda, China

Historical wooden buildings constitute a significant segment of the architectural heritage worldwide. However, these structures are susceptible to component deterioration and structural inclination, potential collapse due to material degradation and the impact of external loads. The fundamental objective in conserving these historical wooden buildings is to safeguard them from such catastrophic failures, thereby preserving their intrinsic value and extending their longevity. To address this issue, a scientific control method based on the principle of minimum intervention has been proposed, termed the “zero-interference method”. This approach is designed to mitigate the progression of structural inclination and enhance the seismic resilience of ancient wooden structures without imposing any disruptive influences. The ancient wooden building is surrounded by an external protection structure (EPS) that is connected to the inclined part. This study uses the FE model of the Yingxian wooden pagoda in China to analyze the structural responses in both pre- and post-reinforcement, validating the effectiveness of the method. Additionally, the parameters of the EPS are discussed. The results reveal that the zero-interference method can effectively mitigate the progression of structural inclination and reduce the seismic responses of the wooden pagoda. The maximum reduction of story drift can reach over 50 %. The wooden pagoda is connected to an EPSwith concentrically braced support by using BRBs, improving the seismic performance. Notably, this study offers a valuable contribution to the field, presenting a methodological framework for augmenting the structural rigidity and curtailing displacement in historical wooden buildings.

Seismic rehabilitation of RC frames with innovative precast U-shaped UHPC jackets: Experimental evaluation and computational simulation

The rehabilitation of post-earthquake reinforced concrete (RC) frames is crucial for both restoring structural integrity and enhancing seismic resilience against future seismic events. Ultra-high-performance concrete (UHPC) is distinguished by its exceptional strength, crack-control capabilities, ductility, and durability. Despite numerous studies on its use for structural retrofitting, its application in rehabilitating damaged RC frames remains limited. This study introduced a novel precast U-shaped UHPC jacket designed for the post-earthquake rehabilitation of RC frames. The jacketing method promotes composite action in rehabilitated members through lap splicing and dowel bars, complemented by cast-in-place connections using UHPC to minimize splice length and strengthen potential weak areas under external loads. The efficacy of this jacketing approach was rigorously evaluated through cyclic loading experiments on two RC frame specimens. Results indicated that the UHPC rehabilitation method not only recovered but significantly enhanced the seismic performance of the previously damaged frame, improving initial stiffness, yield strength, peak strength, displacement ductility, and energy dissipation capacity. However, the rehabilitated frame showed a reduced yield drift and increased residual displacement compared to the as-built frame. The experimental results also revealed the necessity of accounting for bond slip in structural rehabilitation analysis and design to prevent overestimating lateral stiffness. Furthermore, the study developed a computational model that incorporates flexure, bond slip, and shear responses, aiming to effectively simulate the load-displacement behavior of rehabilitated RC frames with reasonable accuracy.

Synthesis and Characterization of Electrospun Ni-BZY Nano-Fiber Anodes

Solid oxide fuel cell (SOFC) and related Protonic Ceramic Fuel Cell (PCFC) technologies have demonstrated significant promise for the efficient and clean electrochemical conversion of stored energy held in a wide variety of renewable fuels, decreasing dependence on traditional fossil fuels. The high efficiencies of both devices arise from the direct chemical-to-electrical energy transformation, achieved without moving parts and the losses inherent to combustion technologies. As in all fuel cells, electrons are generated via oxidation of fuel at the anode to power an external load before returning to the cathode to reduce an oxidant, usually O2. Separating the two electrodes is a dense, gas-tight, electronically insulating electrolyte that permits ion diffusion to complete the circuit. The SOFC’s solid oxide electrolyte passes oxides from the cathode to the anode, but the large activation barrier associated with this process requires high operating temperatures (≥700 ˚C), exacerbating degradative processes and adding challenges for thermal management. In contrast, the PCFC’s perovskite electrolyte permits protonic diffusion from the anode to the cathode, with a smaller activation barrier leading to lower operating temperatures (450 – 700 ˚C). Despite recent advancements in emerging PCFC materials, the overall efficiency and long-term stability of the device is still impacted in part by the anode’s ability to catalyze fuel oxidation, generate protons, and shuttle electrons to an attached current collector. These processes in turn are strongly linked to the morphology and stability of the anode—often a cermet composed of a Ni catalyst/electronic conductor and protonic ceramic such as yttrium-doped barium zirconate (BZY). In particular, continuity is needed for the Ni, BZY, and pore networks while maximizing boundaries between each phase (three-phase boundary). Traditionally, anodes are fabricated by mixing appropriate powders together without much control over the morphology over the micron-sized components. In this study, we explore an alternative approach to systematically engineer Ni-BZY nanofibers within the anode to enhance overall device performance through improving the underlying electrochemical processes at the anode. Low nickel-content BZY anodes (<40 wt. % Ni) for PCFCs are fabricated through electrospinning, with two distinct methods evaluated for nickel loading. First, uniform BZY nanofibers are synthesized by electrospinning a gel containing BZY metal cations and 5 wt. % Polyvinylpyrrolidone (PVP) as dispersant in ethanol/acetic acid solution followed by sintering at 900°C for 3 h in air, and subsequent electroless deposition of nickel on the fiber surfaces. Second, Ni-BZY is prepared by electrospinning a polymer containing a nickel salt and the same BZY precursors followed by co-sintering at 900°C for 3 h. The Ni-BZY fibers underwent morphological, crystallinity and elemental characterization via SEM, XRD, TEM and Raman microscopy. Initial comparison of the fibers fabricated by both methods has shown that uniform nickel loading of ~35 wt. % on the fibers was achieved in the second method. Slurries containing fibers made from both methods are deposited as anodes onto BZY electrolytes, and the complete cells are tested electrochemically under hydrogen at elevated temperature and compared with a control PCFC constructed using conventional powder materials with comparable nickel loading. In summary, electrospun nanofibers, known for their excellent permeability and faster charge transfer due to their porous structure, present an intriguing alternative for high-performance PCFC anode materials. Figure 1

Characterizing PFASs in aquatic ecosystems with 3D hydrodynamic and water quality models

Understanding how per- and polyfluoroalkyl substances (PFASs) enter aquatic ecosystems is challenging due to the complex interplay of physical, chemical, and biological processes, as well as the influence of hydraulic and hydrological factors and pollution sources at the catchment scale. The spatiotemporal dynamics of PFASs across various media remain largely unknown. Here we show the fate and transport mechanisms of PFASs by integrating monitoring data from an estuarine reservoir in Singapore into a detailed 3D model. This model incorporates hydrological, hydrodynamic, and water quality processes to quantify the distributions of total PFASs, including the major components perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), across water, particulate matter, and sediments within the reservoir. Our results, validated against four years of field measurements with most relative average deviations below 40%, demonstrate that this integrated approach effectively characterizes the occurrence, sources, sinks, and trends of PFASs. The majority of PFASs are found in the dissolved phase (>95%), followed by fractions sorbed to organic particles like detritus (1.0–3.5%) and phytoplankton (1–2%). We also assess the potential risks in both the water column and sediments of the reservoir. The risk quotients for PFOS and PFOA are <0.32 and < 0.00016, respectively, indicating an acceptable risk level for PFASs in this water body. The reservoir also exhibits substantial buffering capacity, even with a tenfold increase in external loading, particularly in managing the risks associated with PFOA compared to PFOS. This study not only enhances our understanding of the mechanisms influencing the fate and transport of surfactant contaminants but also establishes a framework for future research to explore how dominant environmental factors and processes can mitigate emerging contaminants in aquatic ecosystems.

Entrance process and interface distribution of nanoparticles in point contact

Nanoparticles have proven to be effective in reducing friction and wear in tribological systems. Previous research mainly focused on the behavior of nanoparticles within the contact region, often overlooking the dynamics of particle's ingress into the interface. This study introduces an innovative model to elucidate the entry process of particles in point contact, grounded in mechanical analysis. The model is employed to investigate the distribution and load-bearing capacity of nanoparticles within the interface, considering variables such as velocity, applied load, particle concentration, particle size, and friction coefficient. Relative ball-on-disk experiments were conducted to verify the model’s prediction, with particular attention to the elemental distribution of particles along the wear tracks. Both theoretical and experimental results indicate that the distribution of particles shifts from covering the whole contact interface to concentrating at the edge in the movement direction as the external load increases and the velocity decreases. Additionally, while the spatial distribution of particles remains constant, the particle concentration within the interface significantly increases with higher nanoparticle concentrations. The enhanced tribological performance of nanofluid is attributed to a greater number of particles entering the contact region.

Impact of Lean-Burn Combustor Flow on Nozzle Guide Vane Performance

Abstract In this paper we investigate the impact of lean-burn-representative swirl and temperature distortion on the aerothermal performance of fully-cooled high-pressure nozzle guide vanes (NGVs) from a modern aero-engine. Experiments were carried out in the Engine Component AeroThermal (ECAT) facility at the University of Oxford. This is a fully-annular warm-flow engine parts facility, designed to operate at engine-representative conditions of Reynolds and Mach number. Inlet profiles of swirl, turbulence, and non-dimensional total temperature were generated using a non-reacting combustor simulator. The NGV outlet flow was experimentally characterized at three downstream planes in experiments with and without lean-burn-representative inlet conditions. Area-survey measurements included distributions of whirl angle, kinetic energy (KE) loss, and non-dimensional total temperature. Experimental data is compared to computational fluid dynamics (CFD) simulations. Fully-featured NGV geometry (including film cooling holes and internal passages) was used, to account for internal cooling flow redistribution resulting from altered external loading. We show that lean-burn inlet conditions result in significant surface flow redistribution, relatively high levels of residual swirl in the downstream flow, and a small increase of integrated KE loss.

Training Load Monitoring in Elite Youth Women's Artistic Gymnasts: A Pilot Study.

Women's artistic gymnastics (WAG) is a complex aesthetic sport in which athletes start at a young age and are exposed to high loads during their careers. Little is known about the external and internal training load characteristics among elite young gymnasts. High training loads, with variations over the weeks, are expected. There is a relationship between external and internal load variables. Cohort study. Level 3. Seven elite-level Brazilian youth artistic gymnasts (age, 11.3 ± 0.4 years; mass, 33.0 ± 7.0 kg; height, 137.7 ± 10.6 cm; experience, 4.0 ± 1.2 years) participated in this study. Five nonconsecutive microcycles were monitored. Both external and internal training loads were quantified by counting the number of elements in video recordings of training sessions and by the session rating of perceived exertion method. A total of 168 individual training sessions were monitored. The microcycle that succeeded the main competition showed a significantly lower training load than ≥3 of the other 4 microcycles for all training load variables, except for vault elements, of which microcycle 4 was inferior only to the microcycle before the competition. Significant correlations were found between weekly internal training load and the total of elements and elements performed on uneven bars. Youth women's artistic gymnasts present fluctuations in external and internal training load variables over the weeks close to a major competition. Training load management in this sport must consider the specificity of each apparatus, as they have different demands and training load behaviors. A better comprehension of external and internal training loads in youth WAG and its apparatuses can benefit coaches and support staff and provide more information to overcome the challenge of training load management in gymnastics.

Supercapacitor-Assisted Energy Harvesting Systems

Energy harvesting from energy sources is a rapidly developing cost-effective and sustainable technique for powering low-energy consumption devices such as wireless sensor networks, RFID, IoT devices, and wearable electronics. Although these devices consume very low average power, they require peak power bursts during the collection and transmission of data. These requirements are satisfied by the use of energy-storage devices such as batteries or supercapacitors (SCs). Batteries offer significantly higher energy density but are subject to regular replacement, thermal runaway risk, and environmental concerns. On the other hand, SCs provide over a million-fold increase in capacitance compared to a traditional capacitor of the same volume. They are considered as the energy-storing devices that bridge the gap between conventional capacitors and batteries. They also offer fast charging times, a long lifecycle, and low equivalent series resistance (ESR). Most importantly, they are capable of handling the high transient currents produced by energy harvesters and provide a stable power source for external loads. This study encompasses a brief exploration of the three fundamental SC types. Then, the discussion delves into the integration of SCs into energy harvesting applications. The collective knowledge presented aims to guide future research endeavors fostering the development of novel energy harvesting systems using SCs.

Acoustic Radiation Characteristics of a Forced Vibrating Elastic Panel Under Thermal Environments

This paper presents the thermo-acoustic frequency response of an un-baffled rectangular panel subjected to an external excitation load. A boundary element method BEM has been employed taking into account the Kirchhoff-Helmholtz K-H integral equation for the acoustic pressure and with the fluid-plate interface boundary condition the acoustic pressure jump over the panel is calculated. The thermal effects are considered regarding in the form of a uniform increment of temperature of the panel and are analysed in order to prevent the buckling phenomena. The excitation force considered is in the form of a concentrated load at some point of the panel and the deformation modes correspond to the vacuum case. Applying a collocation method for the panel equation, a frequency transfer function is obtained that relates the deflexion of the panel with the applied load. The effect of several geometric parameters, different thermal loads and location of the load applied on the acoustic radiated power and the acoustic efficiency spectrum are evaluated. Furthermore, the influence of the excitation frequency on the sound directivity is evaluated. The verification of the method is proven with other works.

AcousTac: Tactile Sensing with Acoustic Resonance for Electronics-Free Soft Skin.

Sound is a rich information medium that transmits through air; people communicate through speech and can even discern material through tapping and listening. To capture frequencies in the human hearing range, commercial microphones typically have a sampling rate of over 40 kHz. These accessible acoustic technologies are not yet widely adopted for the explicit purpose of giving robots a sense of touch. Some researchers have used sound to sense tactile information, both monitoring ambient soundscape and with embedded speakers and microphones to measure sounds within structures. However, these options commonly do not provide a direct measure of steady state force or require electronics integrated somewhere near the contact location. In this work, we present AcousTac, an acoustic tactile sensor for electronics-free, force-sensitive soft skin. Compliant silicone caps and plastic tubes compose the resonant chambers that emit pneumatic-driven sound measurable with a conventional off-board microphone. The resulting frequency changes depend on the external loads on the compliant endcaps. The compliant cap vibrates with the resonant pressure waves and is a nonidealized boundary condition, initially producing a nonmonotonic force response. We characterize two solutions-adding a distal hole and mass to the cap-resulting in monotonic and nonhysteretic force readings with this technology. We can tune each AcousTac taxel to specific force and frequency ranges, based on geometric parameters including tube length, and thus uniquely sense each taxel simultaneously in an array. We demonstrate AcousTac's functionality on two robotic systems: a 4-taxel array and a 3-taxel astrictive gripper. Simple to implement with off-the-shelf parts, AcousTac is a promising concept for force sensing on soft robotic surfaces, especially in situations where electronics near the contact are not suitable. Equipping robots with tactile sensing and soft skin provides them with a sense of touch and the ability to safely interact with their surroundings.

A Fully Coupled Model for Predicting Geomechanical and Multiphase Flow Behaviour in Fractured Rocks

Geomechanical and multiphase flow characteristics are essential in recovering oil from naturally fractured rocks during hydrocarbon production because of changes in pore pressure and tension within the rock. It is a well-established fact that the geomechanical and multiphase flow characteristics of fractured rocks are interdependent on each other. Evaluation of these characteristics, for hydrocarbons displaced by water in fractured rocks under external stress loading, is severely lacking in published literature. This study aims to develop a novel numerical framework for a fully coupled model of fractured rocks, taking into consideration the pore pressure and porous media discontinuity at the fracture-matrix interface, along with an expanded Darcy's equation. The fully coupled Finite Element Method (FEM) and Computational Fluid Dynamics (CFD) model developed in this study is shown to accurately predict geomechanical and multiphase flow behaviour at the fracture-matrix interface. The results show that as external stress loading on the fractured rock increases, the porosity and permeability of the rock matrix decrease, capillary pressure at the fracture-matrix interface decreases, and the relative permeability curves shift to the right, indicating a water-soaked fracture-matrix interface. The findings of this study can be used to develop innovative strategies for enhanced oil recovery from fractured rocks.

Adhesive strength improvement by providing steps in joints and differentiating initial and final debonding stresses

Step adhesive joints have a special characteristic quite different from other joints. When initial delamination occurs in other joints such as butt, lap and scarf joints, final failure always occurs. In these cases, the external stress causing initial delamination σcInitial is equal to the final failure stress asσcFinal = σcInitial. However, in step joints, the final failure stress σcFinalcan be greater than the initial delamination stress σcInitial < σcFinal. To clarify the adhesive improvement mechanism, first, this paper discusses the ISSF (Intensity of Singular Stress Fields) for fully bonded step joint by varying the number of steps NS. Second, the singular stress field causing 2nd debonding is discussed by analyzing partially delaminated step joint. The results show that 2nd debonding requires larger external load than the initial debonding as σcInitial < σcFinal. This is because under the same external load the singular stress causing the 2nd deboning is smaller than the one causing the initial debonding. When NS≥6 and suitable overlap length, the final bond strength σcFinal can be more than 3.6 ∼ 4.4 times larger than the initial delamination stress σcInitial≪σcFinal resulting in much larger bond strength

Application of fractal analysis to characterise the fracture and mechanical properties of concrete.

Abstract Concrete structures consist of cracks even under service loads. The presence of micro-cracks and other flaws such as pores and voids act as potential sources for crack propagation leading to fracture under external loadings. Irregularities produced during the fracturing process in concrete are manifested on the fracture surface, characterizing it as fractal. Therefore, the investigation and quantification of the fractal pattern exhibited by fracture surfaces have become a focal point of research in recent years. In this work, beam specimens made with four different concrete mixes underwent a three-point bending test in order to determine a correlation between the fracture energy and mechanical characteristics of concrete. Concrete’s mechanical characteristics and fracture energy are discovered to be positively correlated. The fractal analysis is done using an LVDT instrument. Using a program written in MATLAB code, the fractured surface is regenerated with measured undulations. Concrete’s flexural strength and fracture energy are then connected with the fractal dimension value that was found. In conclusion, it was observed that a strong correlation exists between the fractal dimension value and fracture energy.

Changes in Hip Isometric Strength of Female College Soccer Players After High-Workload Training Session.

The hip adductor and abductor muscles play vital roles as stabilizers in the lower-extremity. Their activation during soccer-specific actions is essential, but local muscular fatigue can hinder athletic performance and increase the risk of injury. This study aimed to observe the variations in frontal plane hip strength in female college soccer players before and after ahigh-workload soccer-specific training session. Furthermore, the study sought to compare the relative changes in hip strength with the internal and external load measures obtained during that session. Twenty female college soccer players participated in a retrospective observational study. Isometric hip adductor and abductor strength were measured before and after a training session in the college spring season. Measurements were taken with a handheld dynamometer (MicroFET 2) while the players were supine. Global positioning system sensors (Catapult Vector S7), commonly worn by players during training sessions and competitive matches, were used to measure external and internal loads. Statistical analyses were performed using paired samples t test to assess hip adductor and abductor strength changes before and after the training session. Spearman rank was used to identify correlation coefficients between global positioning system data and isometric hip strength. The findings revealed significant decreases in the strength of the right hip adduction (P = .012, -7% relative change), right abduction (P = .009, -7.6% relative change), and left abduction (P = .016, -4.9% relative change) after the training session. Furthermore, relative decreases in hip isometric adduction and abduction strength are related to the distance covered at high speeds. The results of this study highlight that hip isometric adduction and abduction strength tend to decrease after exposure to high workloads during soccer-specific training.