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Flexible regulation of airport air-conditioning systems: Impact of cooling load variations on temperature stability

The integration of renewable energy sources has led to notable supply-demand imbalances due to their intermittent nature. Air-conditioning systems, as significant energy consumers with considerable flexibility, play a crucial role in integrating renewable energy and regulating power systems. This paper delves into the capability of air-conditioning systems in airports to flexibly adjust, particularly examining how varying cooling loads impact indoor temperatures. The energy flexibility of the air-conditioning system is evaluated based on three fundamental cooling load variations (incremental, translational, and discrete), and several evaluation parameters are defined. For areas with smaller cooling load fluctuations, there is a greater adjustment margin, but long adjustment periods should be avoided. For areas with larger fluctuations, the original cooling load curve should be considered in the adjustment strategy. The simulation results show that advancing or delaying the supply by 1 hour during peak cooling load periods can ensure indoor temperature stability, and step-type cooling load curves do not adversely affect indoor comfort levels. Practical case studies further demonstrate that utilizing water storage as an active regulation strategy can reduce operational costs by 26%, and with flexible adjustments, this reduction can increase to 35-54%. The study offers a framework to optimize air-conditioning flexibility in airports, facilitating better renewable energy integration and grid stability, which holds significant potential to reduce costs and improve energy efficiency, thus contributing to sustainable energy management.

ADJUSTMENT OF THE ELEMENTS OF THE FLOW PART OF THE HIGH-EFFICIENCY OF PUMP- TURBINE

The problem of the development of pumped storage power plants in Ukraine is considered, especially in the conditions of military operations, which damaged the energy infrastructure and created capacity shortage. The pumped storage power plants will help stabilize the power system by storing energy during periods of low load and efficiently using it during peak needs or accidents. All this has a positive impact on the role of energy autonomy and the integration of renewable energy sources. Efficiency increase of the hydro-turbine equipment of the PSPP requires the improvement of the water passage of the reversible hydraulic machines. This work shows that the creation of high-efficiency reversible hydraulic equipment depends on the correct selection of the geometry of the pater passage elements of the reversible hydraulic machines, consequently ensure the necessary level of energy characteristics of the hydraulic equipment. The equation of the optimal mode was used for the calculated assessment of kinematic and energy characteristics, analysis of their formation and search for rational variants that provide the specified requirements for the runner energy characteristics of the reversible hydraulic machines. Calculations are carried out using dimensionless kinematic parameters, which simplifies the process and eliminates the need for complex calculations. The numerical analysis data on the influence of the hydrodynamic parameters of the water passage on the parameters of the optimal mode can be used both for profiling the blade system of the runner, with the aim of improving energy characteristics (increasing power, efficiency level, etc.), and for modifying the blade system. The numerical study method for finding optimal variants of the runner blade system is given. The proposed approach was used to estimate the kinematic and energy characteristics of water passages of Francis turbines, as well as high-head reversible hydraulic machines ОRО200 and ОRО500 (both for basic and modified variants of the water passage).

Laboratory evaluation of calcareous sand specimens with inclined sedimentary surfaces

Sedimentary processes often produce natural and blown calcareous sands that are deposited in inclined and layered formations. These calcareous sands frequently exist in a complex stress state with rotating principal stress axes that result in intricate mechanical properties. To investigate the mechanical behaviors of calcareous sands with inclined sedimentary surfaces, we developed a device to prepare hollow cylindrical specimens from artificially crushed calcareous sands. By combining this device with a hollow cylindrical torsional shear apparatus, undrained monotonic loading and pure principal stress rotation tests were conducted to investigate the static and dynamic properties of the inherently anisotropic calcareous sands. The results indicate that the shear dilatancy property is related to the principal stress direction; the shear dilatancy of calcareous sand decreases as the direction of the principal stress increases, and the peak stress ratio decreases with increasing principal stress direction and increases with increasing deposition direction. In the precyclic loading period, increases in the deposition direction led to increases in the stabilities of the specimens and decreases in excess pore pressure accumulation, which further affect the dynamic shear modulus and damping ratio of the calcareous sand. In the late stage of cyclic loading, the inherent anisotropies of the specimens are destroyed, so that the excess pressure and hysteresis loop characteristics start to converge.

Optimized shock-protecting microstructures

Mechanical shock is a common occurrence in various settings, there are two different scenarios for shock protection: catastrophic protection (e.g. car collisions and falls) and routine protection (e.g. shoe soles and mattresses). The former protects against one-time events, the latter against periodic shocks and loads. Common shock absorbers based on plasticity and fracturing materials are suitable for the former, while our focus is on the latter, where elastic structures are useful. Further, we optimize the effective elastic material properties which control the critical shock parameter, maximal stress, with energy dissipation by viscous forces assumed adequate. Improved elastic materials protecting against shock can be used in applications such as automotive suspension, furniture like sofas and mattresses, landing gear systems, etc. Materials offering optimal protection against shock have a highly non-linear elastic response: their reaction force needs to be as close as possible to constant with respect to deformation. In this paper, we use shape optimization and topology search to design 2D families of microstructures approximating the ideal behavior across a range of deformations, leading to superior shock protection. We present an algorithmic pipeline for the optimal design of such families combining differentiable nonlinear homogenization with self-contact and an optimization algorithm. We validate the effectiveness of our advanced 2D designs by extruding and fabricating them with 3D printing technologies and performing material and drop testing.

Project Report: Thermal Performance of FIRSTLIFE House

The paper deals with selected thermal properties of a small building that was built during the international student competition Solar Decathlon 2021/2022 and is now part of the Living Lab in Wuppertal. It summarizes the essential information about the overall design of this wooden building with construction and technologies corresponding to the passive building standard. Built-in sensors and other equipment enable long-term monitoring of thermal parameters. Part of the information comes from the building operation control system. The thermal transmittance value for the perimeter wall matches calculated expectation well, even from a short period of time and not at an achievable perfectly steady state boundary condition. The (positive) difference between the calculated values and the measured ones did not exceed 0.015 W/(m2K). It was proven that even for such a small building with a very small heat demand, the heat transfer coefficient can be estimated alternatively from a co-heating test (measured electricity power for a fan heater) and from energy delivered to underfloor heating (calorimeter in heating system). Differences among both measurement types and calculation matched in the range ± 10%. In the last section, the dynamic response test is briefly described. The measured indoor air temperature curves under periodic dynamic loads (use of fan heater) are compared with the simulation results. The simulation model working with lumped parameters for each element of the building envelope was able to replicate the measured situation well, while its use does not require special knowledge of the user. In the studied case, the differences between measured and simulated air temperatures were less than 1 Kelvin if the first two to three days of the test period are ignored due to large thermal inertia. Finally, the measurement campaign program for the next period is outlined.

Innovative Strategies for Tannery Wastewater Remediation with Sequential batch reactor and phycoremediation

<p style="line-height:150%;text-align:justify;"><span style="font-family:"Times New Roman",serif;font-size:12.0pt;" lang="EN-IN">This research assessed the performance of combining Sequential Batch Reactor (SBR) and phycoremediation method used for tanning effluent. The SBR system obtained high removal efficiencies with Chemical Oxygen Demand (COD)  is reduced by  85%, Biological Oxygen Demand (BOD) is reduced  by 80% as well as ammonia by more than 75%. Chromium and lead were dropped by 65% and 60% correspondingly after treatment. Following SBR process, inclusion of Chlorella vulgaris in the phycoremediation stage further improves the removal of pollutants achieving 95% COD and 92% BOD reductions. Heavy metal removal was enhanced with chromium and lead by reducing 85% each. Kinetic analysis indicated that ammonia and COD removal followed first-order kinetics with high model fit (R2=0.93 for COD; R2=0.91 for ammonia). Heavy metal removal using Chlorella vulgaris also conformed to first-order kinetics. A temporary increase in ammonia levels was observed due to nitrification inhibition during periods of high organic loads in the wastewater discharged from tanneries into rivers or lakes without treatment facilities such as oxidation ditches or stabilization ponds used in some cases. Finally, it can be concluded that an integrated SBR phycoremediation process shows very good potentialities with respect to good performances in treating wastewater efficiently.</span></p>

Youth and Adolescent Athlete Musculoskeletal Health: Dietary and Nutritional Strategies to Optimise Injury Prevention and Support Recovery.

Background: Despite the well-documented benefits of exercise and sports participation, young athletes are particularly vulnerable to musculoskeletal injuries. This is especially true during periods of rapid growth, sports specialisation, and high training loads. While injuries are an inevitable aspect of sports participation, the risk can be minimised by promoting the development of strong, resilient tissues through proper nutrition and injury prevention strategies. Moreover, targeted nutrition strategies can accelerate recovery and rehabilitation, allowing for a quicker return to sports participation. Methods: This narrative review synthesises scientific evidence with practical insights to offer comprehensive dietary recommendations aimed at strengthening tissues and supporting the healing process during recovery and rehabilitation. The selection of all sources cited and synthesised in this narrative review were agreed upon by contributing author consensus, experts in sports nutrition (R.A., H.V., B.D.) and exercise and sports medicine (M.H.). Results: Key topics include factors that contribute to injury susceptibility, general dietary recommendations for growth and development, sports nutrition guidelines, and nutrition considerations during injury and rehabilitation. This review also addresses external factors that may lead to suboptimal nutrition, such as food literacy and eating disorders. Conclusions: By highlighting these factors, this article aims to equip coaches, nutritionists, dietitians, athletic trainers, physical therapists, parents/guardians, sporting organisations, and schools with essential knowledge to implement effective nutritional strategies for injury prevention, recovery, and rehabilitation, ultimately enhancing long-term health and athletic performance.

Long Duration Load Carriage Performance Is Associated With Army Combat Fitness Test Scores and Fat-Free Mass.

Sax van der Weyden, M, Merrigan, JJ, and Martin, J. Long duration load carriage performance is associated with Army Combat Fitness Test scores and fat free mass. J Strength Cond Res 38(11): 1959-1966, 2024-A common occupational task for the military is carrying heavy loads for long periods of time. The US Army has set a time standard of 3 hours to complete a 19.31-km march with a 15.9-kg ruck sack for combat arms training and specialty schools. The purpose of this study was to identify characteristics associated with 19.31-km foot march completion rates in Reserve Officers' Training Corps (ROTC) Cadets. Demographics, anthropometrics/body composition, Army Combat Fitness Test (ACFT) scores, and vertical countermovement jump (CMJ) data were collected on 65 ROTC cadets who conducted a 19.31-km foot march. Independent t tests and Mann-Whitney U tests compared variables between those who did and did not finish the foot march in less than 3 hours. Logistic regressions were used to calculate the odds of completing the foot march using military experience, fat-free mass, ACFT, and CMJ outcomes. Cadets who met the 3 hours standard had lower body fat percent, greater fat-free mass, higher ACFT scores, and higher CMJs than those who did not. In addition, for every one point increase in ACFT score and 1-kg increase in fat-free mass, a cadet's chances of finishing the foot march increased by 6.1 and 24%, respectively. When analyzing ACFT events separately, 2-mile run was the only significant variable, and for every 1 point increase in 2-mile run score, a cadet's chances of finishing the foot march increased by 9%. Thus, aspiring and current soldiers should train to improve aerobic fitness and build muscle mass in preparation for load carriage requirements.

Use of Apple Pomace for Intensification of Biogas Production in the Anaerobic Digestion of Cattle Manure

The goal of the work is to increase the yield of methane in biogas plants due to the joint methane fermentation of cattle manure with apple pomace. To achieve this goal, the following tasks were solved: the yield of biogas from cattle manure was determined with the addition of apple pomace to the substrate and fermentation in psychrophilic and mesophilic temperature conditions of the biogas plant. Based on the obtained experimental data of fermentation at temperatures of 22±1°C and 36±1°C of the fermenter, the biogas yield was assessed and the rational temperature regime for the operation of the biogas plant was determined. The studies were carried out on a laboratory biogas plant, consisting of a fermenter and a wet-type gasholder. A glass container with a total volume of 3 dm3 was used as a fermenter. The novelty of the chosen topic lies in the fact that the maximum methane output rate was determined under periodic loading of the fermenter, which for the psychrophilic temperature regime is 0.0033 m3/(kg DOM∙day), and in the mesophilic temperature regime mode 4 times more - 0.012 m3/(kg DOM∙day). The significance of the results lies in the fact that based on the results of the dynamics of methane output during periodic loading of the fermenter, it is possible to predict a constant methane output in industrial biogas plants that operate in a quasi-continuous mode, which will be equal to the maximum methane output during periodic loading of the fermenter.

A Higher-Order Theory for Nonlinear Dynamic of an FG Porous Piezoelectric Microtube Exposed to a Periodic Load

This paper investigates the nonlinear dynamic deflection, natural frequency, and wave propagation in functionally graded (FG) porous piezoelectric microscale tubes under periodic load, hygrothermal conditions, and an external electric field. The piezoelectric material used to make the smart microtubes has pores that may be smoothly changed or uniformly distributed over the tube wall. Here, three types of porosity distribution are taken into consideration. The nonlinear motion equations are constructed using a novel shear deformation beam theory and the modified couple stress theory (MCST). The nonlinear motion equations are solved using the fourth-order Runge–Kutta technique and the Galerkin approach. The effects of various geometric parameters, porosity distribution type, porosity factor, periodic load amplitude and frequency, material length scale parameter, moisture, and temperature on the nonlinear dynamic deflection, natural frequency, and wave frequency of FG porous piezoelectric microtubes are explored through a number of parametric investigations.

Modernization of the PGU-450 thermal circuit with an increase in the thermal power of heating selections and preservation of the total electric power

PURPOSE. Modernization of the PGU with an increase in thermal power and preservation of electrical power using a block afterburning device (BDU) in a heat recovery boiler (CU). METHODS. Comparative studies of the characteristics of the PGU-450 without a BDU and with an installed DBU were conducted results. As a result of comparative studies of the main characteristics of the PGU-450 and the main characteristics of the PGU-450 before and after installation of the DBU in recovery boilers, it was shown that the use of the BDU effectively solves the problem of covering peak thermal loads in the transition periods of the OSP (spring – summer; autumn – winter); the possibility of long-term operation of the BDU during the entire period of operation of the PG unit is shown; it is revealed that it is most advisable to implement the BDU on the PGU blocks for which the obligations under the DPM agreements have expired. By increasing the electric power by 6% (in the heating mode), the payment for power in the KOM market increases; an increase in the electric power of the PGU unit when operating in condensation mode by 11% minimizes the under-supply of power to the OREM at outdoor temperatures above + 15 degrees; Despite a 3% increase in URUE to 190 g/kWh, the electric energy produced remains competitive in the OREM. CONCLUSION. Thus, as a result of the research, it was shown that when the DBU is switched on, the thermal power of the PGU-450 increases to 320 Gcal/hour, which makes it possible to cover the missing thermal power. Thus, the operation of the T-250 in a mode close to condensation with an URUT ee of 350 g / kWh is excluded, and the entire thermal load is covered by the PGU-450, but with a slightly degraded URUT ee of 190 g / kWh. Such a composition of the CHP equipment ensures the maximum possible economic efficiency of the plant in the electricity market with full coverage of heat consumption.

Dynamics of the Euler — Bernoully beam with distributed hysteresis properties

In this paper, we present a new mathematical approach to the analysis of a beam with distributed hysteresis properties. These hysteresis characteristics are described by two methods: phenomenological (Bouc — Wen model) and constructive (Prandtl — Ishlinskii model). The equations for beam are developed using the well-known Hamilton method. We investigate the dynamic response of a hysteresis beam under various external loads, including impulse, periodic and seismic loads. The results of numerical simulations show that the hysteresis beam exhibits differently to external influences as compared to the classical Euler-Bernoulli beam. In particular, under the same external loads, the vibration amplitude and energy characteristics of the hysteresis beam are lower than those of the classical one. These findings can be useful for buildings developers in the design of external load resistant buildings and structures

Bearing Performance of a Helical Pile for Offshore Photovoltaic under Horizontal Cyclic Loading

For an offshore photovoltaic helical pile foundation, significant horizontal cyclic loading is imposed by wind and waves. To study a fixed offshore PV helical pile’s horizontal cyclic bearing performance, a numerical model of the helical pile under horizontal cyclic loading was established using an elastic–plastic boundary interface constitutive model of the clay soil. This model was compared with a monopile of the same diameter under similar conditions. The study examined the effects of horizontal cyclic loading amplitude, period, and vertical loads on the horizontal cyclic bearing performance. The results show that under horizontal monotonic loading, the bearing capacities of a helical pile and monopile in a serviceability limit state are quite similar. However, as the amplitude of horizontal cyclic loading increases, soil stiffness deteriorates significantly, leading to greater horizontal displacement accumulation for both types of piles. The helical pile’s bearing capacity under horizontal cyclic loadings is approximately 60% of that under monotonic loading. With shorter cyclic loading periods, horizontal displacement accumulates rapidly in the initial stage and stabilizes over a shorter duration. In contrast, longer cyclic loading periods lead to slower initial displacement accumulation, but the total accumulated displacement at stabilization is greater. When vertical loads are applied, the helical pile exhibits more stable horizontal cyclic bearing performance than the monopile.

A frequency-dependent model for bone remodeling using a micromorphic porous medium subjected to harmonic mechanical loading

In this paper, the bone tissue was modeled as a linear viscoelastic material saturated with interstitial fluid. We considered a specific case of harmonic loading and related the mechanical stimuli to the loading frequency. In this way, we could include the inertial effect in the model while not having to deal with the perturbation during each loading period. Two types of mechanical signals were considered: strain energy and dissipation energy. A parametric study revealed the dependency of the two signals on loading frequency and material property. The evolution of the apparent mass density supported the parametric study’s findings. Under the three different frequency loadings, the strain energy-stimulated samples experienced identical remodeling scenarios. The samples stimulated with dissipation energy, on the other hand, exhibited a strong frequency dependence. An additional study was performed to investigate the effect of long-term variations in the loading frequency on the remodeling process. This demonstrated the model’s capabilities in designing and evaluating load regimes for rehabilitation following a bone injury or bone reconstruction.

Training Model for Extended Career Athletes: A Narrative Review.

Today's elite and professional sports tend to feature older, more seasoned athletes, who have longer sporting careers. As advancing age can potentially limit peak performance, balancing training load is necessary to maintain an optimal state of performance and extend their sports career. To describe an appropriate training model for extended career athletes. Medline (PubMed), SPORTDiscus, ScienceDirect, Web of Science, and Google Scholar. A search of the literature between January 1, 2015 and November 22, 2023 was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Narrative review. Level 4. Data were extracted from studies related to the management of training and performance of athletes with extended and long careers. A total of 21 articles related to extended careers were found. Key themes from these papers included: expertise, biological maturation, and specificity; epidemiology and health; athlete monitoring; strength training; load management and detraining; success management. A training model for extended career athletes should balance the deleterious effects of age with the athletes' knowledge of, and expertise within, the sport. Designing specific training that accommodates previous injuries, training load intolerances, and caters for quality of life after retirement should be key considerations. Load management strategies for athletes with extended careers should include strength training adaptations to minimize pain, load-response monitoring, a broad range of movement, recovery and intensity activities, and the avoidance of large training load peaks and periods of inactivity.

Decentralized Periodic Dynamic Event-Triggering Fuzzy Load Frequency Control for Multiarea Nonlinear Power Systems Based on IT2 Fuzzy Model

Decentralized Periodic Dynamic Event-Triggering Fuzzy Load Frequency Control for Multiarea Nonlinear Power Systems Based on IT2 Fuzzy Model

Cumulative effects of cyclic train loading on strains in reinforced soils around tunnels

Metro tunnels often experience uneven settlement of the soil beneath them during operation, a problem that is especially pronounced in soft soil layers such as silt. This uneven settlement negatively affects the operational safety of subways, prompting engineers to use soil reinforcement techniques to mitigate ground deformation. However, there is a lack of research on the cumulative deformation of reinforced soils under cyclic train loading. In this study, dynamic triaxial tests were conducted to obtain the deformation parameters of silty reinforced soils under cyclic loading. The principal dynamic relationship was summarized, and the effect of loading frequency on soil deformation was analyzed. The results indicated that as the loading frequency increased, the cumulative deformation of the soil decreased. Using the dynamic constitutive relationship derived from the tests, the finite element method was employed to model the interaction system between the load, tunnel, and strata, as well as the dynamic modulus attenuation behavior of the reinforced soil layer. This approach was used to investigate the cumulative deformation characteristics of reinforced soils under cyclic loading. The findings indicated that the dynamic modulus of the reinforced soil decayed rapidly at the beginning of the loading period, leading to an accelerated increase in the cumulative deformation. Additionally, the cumulative deformation was measured at different train speeds, revealing that when the speeds exceeded 80 km/h, the cumulative strain of the soil increased gradually with speed.

A joint time–space extrapolation approach within the Wiener path integral technique for efficient stochastic response determination of nonlinear systems

A joint time–space extrapolation approach within the Wiener path integral (WPI) technique is developed for determining, efficiently and accurately, the non-stationary stochastic response of diverse nonlinear dynamical systems. The approach can be construed as an extension of a recently developed space-domain extrapolation scheme to account also for the temporal dimension. Specifically, based on a variational principle, the WPI technique yields a boundary value problem (BVP) to be solved for determining a most probable path corresponding to specific final boundary conditions. Further, the most probable path is used for evaluating, approximately, a point of the system response joint probability density function (PDF) corresponding to a specific time instant. Remarkably, the BVP exhibits two unique features that are exploited in this paper for developing an efficient joint time–space extrapolation approach. First, the BVPs corresponding to two neighboring grid points in the spatial domain of the response PDF not only share the same equations, but also the boundary conditions differ only slightly. Second, information inherent in the time-history of an already determined most probable path can be used for evaluating points of the response PDF corresponding to arbitrary time instants, without the need for solving additional BVPs. In a nutshell, relying on the aforementioned unique and advantageous features of the WPI-based BVP, the complete non-stationary response joint PDF is determined, first, by calculating numerically a relatively small number of PDF points, and second, by extrapolating in the joint time–space domain at practically zero additional computational cost. Compared to a standard brute-force implementation of the WPI technique, the developed extrapolation approach reduces the associated computational cost by several orders of magnitude. Two numerical examples relating to an oscillator with asymmetric nonlinearities and fractional derivative elements, and to a nonlinear structure under combined stochastic and deterministic periodic loading are considered for demonstrating the reliability of the extrapolation approach. Juxtapositions with pertinent Monte Carlo simulation data are included as well.

State of the Art on Retrofitting of Fatigue Damaged Concrete Structures

This article provides a general up to date review of the investigation on performances and resistances of plain and fiber containing concrete structures under periodical loadings of long endurance up to fatigue failure. Structures are almost, under the frequent influences of repeated loadings such as vibrations of rotary machines, sea /river waves, wind, earthquakes and moving vehicles. Long term application of cyclic loading leads to continually slow rate degradation of the structure rigidity leading to fatigue damage. In spite of the dominant usage of concrete, worldwide, as a building material, its fatigue behavior is not straight forward. In addition, this lack of comparison is confronted for fiber fortified concrete. The article also presently a survey of the available techniques for monitoring and measurement of fatigue impressions in concrete structures founded both their impact within the treatise domain and the non-destructive inspection. Those technical means are classified into, at least, two designations, specifically, the monitoring of fatigue induced cracking and the detection of fatigue charged damage. Those techniques parameters, evaluate the changes in the mechanical and physical materials properties during the fatigue endurance, are distantly reviewed in concern of the mechanism creating the change, shortcomings, constraints, etc. The merits, dependency, feasibility, disadvantages and limitations of each technique are assessed and compared to make an index to select the appropriated e technique for fatigues fracture or failure inspection of the type fibered or not of structural concrete

Microcracking evolution and clustering fractal characteristics in coal failure under multi step and cyclic loading

During the deep mining process, coal mass encounter intricate geo-environmental stress, such as periodic weighting loading and repeatedly excavation unloading–reloading cycles, which weakens coal’s mechanical integrity and predisposing it to severe coalburst accidents. To investigate the microcracking damage mechanisms and predictive indicators in coal failure under in-situ stress analogs, the multistage step and cyclic loading experiments are conducted on cubic coal specimens. Acoustic emission (AE) technology is employed to track the spatiotemporal-energy evolution of stress-induced damages and discern the microcracking nature through AF/RA assessments, and the power-law scaling relation of AE activity near the catastrophic failure of coal is investigated. Then the clustering fractal structures of microcracking events in the stressed coal are quantified across temporal, spatial and energetic domains, utilizing correlation integral methodologies and b-value derivations from magnitude-frequency relation. Findings indicate that irrespective of the loading mode (step or cyclic), escalating stress triggers an intensification of irreversible fatigue deformations. AE characteristic parameters manifest a gradual rise, culminating in a precipitous peak coinciding with the critical failure point. This escalation adheres to a power-law correlation between AE occurrence frequency and time to failure, observable in the immediate pre-failure seconds, reflecting a universal attribute of coal fracture. Prior to ultimate failure, a marked increase in shear microcracks is discernible, despite tensile-dominated cracks (constituting about 80 % of total microcracks) prevailing as inferred from the variation of AF/RA values, aligning with an inferred “X” conjugate wedge splitting pattern from AE event density and energy mapping. The microcracking events in the loaded coal exhibit a clustering fractal structure that spans across temporal, spatial, and energetic (or magnitude) domains. Notably, the temporal fractal dimension, spatial fractal dimension, and b-value (i.e., a parameter characterized the energetic fractal dimension) all follow a parallel decrease pattern as the loading stress escalates, with a pronounced diminution becoming especially evident as the specimen approaches its catastrophic failure threshold. This insight offers fresh perspectives for predicting rock/coal dynamic disasters, emphasizing the necessity of concurrently monitoring the shift from diffuse microcracking to localized failure across time, space and energy domains. These research findings contribute to a deeper understanding of microcracking damage evolution and failure mechanism of loaded coal, and provide a foundational basis for early warning of rock failure such as the coalburst disasters.