Long-term Load Research Articles

Climatic and Anthropogenic Influences on Long-Term Discharge and Sediment Load Changes in the Second-Largest Peninsular Indian Catchment

In recent decades, understanding how climate variability and human activities drive long-term changes in river discharge and sediment load has become a crucial field of research in fluvial geomorphology, particularly for South Asia’s densely populated and environmentally sensitive regions. This study analyses spatio-temporal trends in water discharge (Qd) and sediment load (Qs) in the Krishna basin, Peninsular India’s second-largest catchment. Using nearly 50 years of daily discharge, sediment concentration, and rainfall data from the Central Water Commission (CWC) and India Meteorological Department (IMD), we applied Mann–Kendall, Pettitt tests, and double mass equations to detect long-term trends, abrupt changes, and the relative influence of climate and anthropogenic effects. Results showed a notable decline in the annual discharge, with 15 of 20 stations showing decreasing trends, especially along the Bhima, Ghataprabha, and lower Krishna rivers. The annual stream flow data showed a 53% decline in the mean Qd from 26.01 × 109 m3 year−1 before 2000 to 12.32 × 109 m3 year−1 after 2000 at the terminal station. Eight of ten gauging stations showed a significant decrease (p-value < 0.05) in their annual sediment load, with a 76% reduction across the Krishna basin after its changepoint in 1983. The Pettitt test identified a statistically significant downward shift in discharge at seven stations. Double mass plots indicate that anthropogenic factors, such as large-scale reservoirs and water diversion, are the main contributors, accounting for 82.7% of sediment decline, with climatic factors contributing 17.1%. The combined trend analysis and double mass plots confirm these findings, underscoring the need for further study of human impacts on the basin’s hydro-geomorphology. This study offers a clear and robust approach to quantifying the relative effects of climate and human activities, providing a versatile framework that can enhance understanding in similar studies worldwide.

A comparative study of long short-term memory based long-term electrical load forecasting techniques with hyperparameter optimization

A comparative study of long short-term memory based long-term electrical load forecasting techniques with hyperparameter optimization

Ultra-high performance concrete with high strength, workability, loading durability and low curing maintenance for applications in airport pavement

With the rapid development of the aviation industry, airport pavement is subjected to ever-increasing loads, posing urgent and higher demands on the mechanical performance and durability of pavement materials. This study develops a novel Ultra-High Performance Concrete (UHPC) with outstanding mechanical properties, good workability, low curing maintenance, and excellent performance in sustaining long-term load to specially designed for its potential application in airport pavement. The as-developed UHPC contains a mixed portion of fine and coarse aggregate, assuring its workability and avoiding the early-age shrinkage crack for the potential on-site construction. With a 7-day compressive strength of 140MPa, compressive strength of 155.1MPa, flexural strength of 25.4MPa at 28 days, and a wear loss per unit area of 0.043kg/m2, the mechanical properties of UHPC well outperform those of conventional C30 airport pavement concrete. Finite element simulation analysis reveals that a 10cm thick UHPC surface layer demonstrates durability and safety under aircraft taxiing and landing impact loads, with a maximum tensile stress of 4.12MPa well below its tensile strength limit of 8.75MPa. Furthermore, it is predicted that a 10cm thick UHPC overlay could support a load cycle lifespan 1014 times longer than that of conventional C30 concrete of 30cm thickness, indicating its potential to significantly extend the service life of airport pavement. This research provides a theoretical basis for the applications of UHPC in airport pavement and presents innovative perspectives on into material and structural design of airport pavement materials for the future.

Decomposition framework for long term load forecasting on temperature insensitive area

Long-term load forecasting (LTLF) with hourly resolution provides more information for power system planning and becomes increasingly important as the growing penetration of renewable energy sources intensifies system uncertainties. In most LTLF literature, temperature is used as the main driving factor. However, the system load in an area with a high proportion of industrial energy consumption or rich diversity of climate zones is less meteorologically sensitive, which makes it challenging to implement LTLF. To address this issue, we propose a decomposition framework with industrial and temperature-sensitive components separated from the electric load and modeled, respectively. For the industrial component, a seldom-used macroeconomic variable, industrial gross products, is fed into modeling. For the temperature-sensitive component, temperature and its variants are input for modeling via variable selection. With serial and parallel modeling schemes, we further propose two decomposition models under this framework, where one, denoted as DeSerial, models two components serially, while the other, denoted as DeParallel, models them in a parallel way. Compared with representative models, the proposed two decomposition models produce more accurate monthly and annual load forecasts for the selected region, whose system load is less sensitive to temperature but more to the industries.

Design and optimization of the jet cooling structure for permanent magnet synchronous motor

Permanent magnet synchronous motor (PMSM) is widely used in electric vehicles due to its high power density and wide speed range. However, when operating under long-term heavy load conditions, PMSM is prone to heat accumulation. It’s difficult to cool the motor with existing indirect cooling structures efficiently, which may lead to its high temperature and result in winding burnout or even permanent demagnetization of the magnets. In this paper, a novel cooling structure based on jet cooling is proposed to reduce the operating temperature of the PMSM efficiently and improve its stability. The temperature field model, which accounts for the influence of end windings, is developed to analyze and optimize the parameters of the jet cooling structure, leading to the determination of an optimal parameter set. By exploring the cooling effects of motors with different cooling structures under stable, extreme and mixed cycle operating conditions, it is proved that the jet cooling structure designed in this paper can effectively reduce the temperature of the motor and ensure its reliable operation. The results show that with the influence of the jet cooling structure designed in this paper, the maximum temperatures of the rotor and winding are reduced by 35.2℃ and 44.5℃ respectively.

Long-term load forecasting for smart grid

Abstract The load forecasting problem is a complicated non-linear problem connected with the weather, economy, and other complex factors. For electrical power systems, long-term load forecasting provides valuable information for scheduling maintenance, evaluating adequacy, and managing limited energy supplies. A future generating, transmission, and distribution facility's development and planning process begins with long-term demand forecasting. The development of advanced metering infrastructure (AMI) has greatly expanded the amount of real-time data collection on large-scale electricity consumption. The load forecasting techniques have changed significantly as a result of the real-time utilization of this vast amount of smart meter data. This study suggests numerous approaches for long-term load forecasting using smart-metered data from an actual distribution system on the NIT Patna campus. Data pre-processing is the process of converting unprocessed data into a suitable format by eliminating possible errors caused by lost or interrupted communications, the presence of noise or outliers, duplicate or incorrect data, etc. The load forecasting model is trained using historical load data and significant climatic variables discovered through correlation analysis. With a minimum MAPE and RMSE for every testing scenario, the proposed artificial neural network model yields the greatest forecasting performance for the used system data. The efficacy of the proposed technique has been through a comparison of the acquired results with various alternative load forecasting methods.

Predicting Fatigue Damage in Hydrogels Through Force-Induced Luminescence Enhancement.

Fatigue damage of polymers occurs under long-term load cycling, resulting in irreversible fracture failure, which is difficult to predict. The real-time monitoring of material fatigue damage is of great significance. Here, tough hydrogels are prepared with force-induced confined luminescence enhancement of carbonated polymer quantum dot(CPD) clusters to realize the visualization of fracture process and the monitoring of fatigue damage. The enhanced interactions induced by force between the clusters and the polymer in the confined space inhibit the non-radiative leaps and promote the radiative leaps to quantify the fatigue damage into optical signals. Rigid CPDs with abundant active sites on the surface can form dynamic reversible bonds with polymer and dissipate stress concentration, which significantly enhances the crack propagation strain (8000%) and fracture energy (26.4kJ m-2) of hydrogels. CPDhydrogelshave a wide range of applications in novel information encryption and luminescent robotics.

Optimizing Models and Data Denoising Algorithms for Power Load Forecasting

To handle the data imbalance and inaccurate prediction in power load forecasting, an integrated data denoising power load forecasting method is designed. This method divides data into administrative regions, industries, and load characteristics using a four-step method, extracts periodic features using Fourier transform, and uses Kmeans++ for clustering processing. On this basis, a Transformer model based on an adversarial adaptive mechanism is designed, which aligns the data distribution of the source domain and target domain through a domain discriminator and feature extractor, thereby reducing the impact of domain offset on prediction accuracy. The mean square error of the Fourier transform clustering method used in this study was 0.154, which was lower than other methods and had a better data denoising effect. In load forecasting, the mean square errors of the model in predicting long-term load, short-term load, and real-time load were 0.026, 0.107, and 0.107, respectively, all lower than the values of other comparative models. Therefore, the load forecasting model designed for research has accuracy and stability, and it can provide a foundation for the precise control of urban power systems. The contributions of this study include improving the accuracy and stability of the load forecasting model, which provides the basis for the precise control of urban power systems. The model tracks periodicity, short-term load stochasticity, and high-frequency fluctuations in long-term loads well, and possesses high accuracy in short-term, long-term, and real-time load forecasting.

Remaining useful life prediction of flax fibre biocomposites under creep load by acoustic emission and deep learning

Natural fibre composites are increasingly explored for structural applications due to improvements in mechanical performance. For this, damage prognostics are crucial. We integrate acoustic emission (AE) and deep learning techniques to predict the remaining useful life of a flax fibre composite under long-term creep load. Derivatives of cumulative AE features with respect to time, such as cumulative hit and count rates, are introduced to reflect the performance degradation rate of the materials. These proposed features seem more relevant for creep lifespan than traditional AE features. Long short-term memory networks and temporal convolutional networks are adopted to estimate the composite’s remaining useful life. The two models' normalized root mean square errors are below 0.11, less than 20% of the error of a statistical Weibull-distribution benchmark model. Our study demonstrates that AE-based data-driven models can predict the performance degradation of composite materials subject to sustained load.

The contribution of cumulative blood pressure load to dementia, cognitive function and mortality in older adults.

Few studies evaluated the contribution of long-term elevated blood pressure (BP) towards dementia and deaths. We examined the association between cumulative BP (cBP) load and dementia, cognitive decline, all-cause and cardiovascular deaths in older Australians. We also explored whether seated versus standing BP were associated with these outcomes. The Sydney Memory and Aging Study included 1037 community-dwelling individuals aged 70-90 years, recruited from Sydney, Australia. Baseline data was collected in 2005-2007 and the cohort was followed for seven waves until 2021. cSBP load was calculated as the area under the curve (AUC) for SBP ≥140 mmHg divided by the AUC for all SBP values. Cumulative diastolic BP (cDBP) and pulse pressure (cPP) load were calculated using thresholds of 90 mmHg and 60 mmHg. Cox and mixed linear models were used to assess associations. Of 527 participants with both seated and standing BP data (47.7% men, median age 77), 152 (28.8%) developed dementia over a mean follow-up of 10.5 years. Higher cPP load was associated with a higher risk of all-cause deaths, and cSBP load was associated with a higher risk of cardiovascular deaths in multivariate models ( P for trend < 0.05). Associations between cPP load, dementia and cognitive decline lost statistical significance after adjustment for age. Differences between sitting and standing BP load were not associated with the outcomes. Long-term cPP load was associated with a higher risk of all-cause deaths and cSBP load associated with a higher risk of cardiovascular deaths in older Australians.

A Study on the Mechanical Behavior of a Wind Turbine Foundation with a Constrained Structural Shear Connector

Aiming to solve the problems that a wind turbine foundation with a foundation pipe may suffer from grouting, where the concrete around the interface collapses and the interface disintegrates under a long-term wind load, a kind of wind turbine foundation with a constrained structural shear connector is proposed. In this article, the scaling model tests and a finite element simulation of a traditional stud foundation pipe, perforated steel shear connector foundation pipe, and three groups of constrained structural shear connector foundation pipes with different anchored depths are presented. The force transmission mechanism and damage mechanism of constrained structural shear connector wind turbine foundations are revealed, and the shear resistance of a constrained structural shear connector is analyzed. The influences of buried depth and other parameters on the mechanical properties of the shear connector are also investigated. The results show that the constrained structural shear connector has the advantages of stronger interfacial stiffness and significant force transfer and diffusion, and can more effectively connect the foundation pipe and concrete foundation to work together. It can give full play to the material advantages of concrete and reinforcements, and effectively improve the embedded stiffness and durability of concrete foundations. It can solve the problem of cracks in concrete caused by local pressure. At the same time, it is suggested that the diameter of the surrounding concrete should be in the range of 3 to 4 D, and the embedment depth of the stud should not be less than 0.4 D to give full play to the performance of the constrained structural shear connector.

Enhanced Transformer Overcurrent Protection via Oil Temperature Acceleration

When a transformer is in a long-term heavy load operation state, the oil temperature reaches the alarm temperature; if a slight fault occurs inside the transformer, traditional inverse time current protection and other protections that react to phase current may not operate due to insufficient sensitivity or they may operate for too long. Based on this, this article proposes a new principle of accelerating inverse time overcurrent protection based on transformer oil temperature. The proposed method uses transformer oil temperature to accelerate the action time of traditional inverse-time overcurrent protection, then introduces the transformer oil temperature factor and acceleration index to optimize the inverse time characteristic curve, and establishes a mathematical model to optimize the adjustment for the complexity of adjustment of the protection action equation and the risk of mismatch of the protection after the acceleration of oil temperature. The existing theoretical analysis and simulation verification results show that the proposed new overcurrent protection scheme based on the transformer oil temperature acceleration inverse time can effectively improve the protection of the rapidity and sensitivity, providing a new research idea for the combination of non-electrical and electrical quantity protection.

СТІЙКІСТЬ ЗАЛІЗОБЕТОННИХ СТІЙОК ПРИ КОРОТКОЧАСНІЙ ТА ТРИВАЛІЙ ДІЇ НАВАНТАЖЕННЯ

The behavior of hinged support at the ends of the rack with initial bending under the action of load is considered. Spring rods are arranged symmetrically. The rack has an initial bend, compressed by forces constant in time. All real elements have one or another imperfections in the form of technological bends, therefore, they begin to bend from the very beginning of the load. The load, when it is exceeded even by an infinitesimally small amount, there is a loss of stability of this type of deformation, is called critical. In the calculation of stability under the long-term action of external forces, it is necessary to determine the load, at which the rate of movement in time monotonically decays. Solving the problem in such a setting is acceptable for systems, the development of movements of which in time leads to a change in the stress state. This condition for a compressed rack is fulfilled only in the presence of initial imperfections (initial bending, off-center application of compressive force, etc.). When solving the problems of the theory of stability, taking into account the creep of the material plays an important role. Creep can be limited in time or unlimited. When solving the problem of the stability of racks with initial imperfections, made of a material that has creep and reinforced with elastic rods, the following assumptions are made: 1) the hypothesis of flat sections is considered valid; 2) the deformations of the creeping material and the elastic rods at the points of contact are the same; 3) the modulus of deformations during stretching and compression are equal; 4) the creep material works in the stretched zone without the appearance of cracks. The relationship between deformations and elasticities in the material of the rack is established by a formula based on the linear relationship between deformations and elasticities. The creep rate of concrete is based on the hereditary theory of aging. In the work, an integro-differential equation was obtained - the equation of slow motion of the rod, expressions were obtained for the study of bends in any at what point in time, the formula for determining the critical force with long-term load action is derived.

Long-term effects including shrinkage and interfacial creep on bond behavior of concrete-filled steel tubes (CFST): Experiment and design

Concrete-filled steel tubes (CFST) are widely used in significant projects due to their high performance stemming from full utilization of combined material advantages. The interfacial bond behavior is the foundation of their high performance, but will deteriorate during the long-term service. Due to the difficulties on carrying out long-term experiments and decoupling the multi-constitutive component bond strength including chemical adhesion, micro-interlocking and friction, there is still a lack of research on long-term interface constitutive models, restricting the safe design of CFST structures throughout their full-lifecycle. Here, push-out tests were carried out on CFST specimens considering long-term effects spanning 850 days including concrete age and duration of long-term interfacial load. The steel plate-concrete specimens, reversed push-out tests and interfacial normal pressure calculation were used to decouple the components of bond stress. the CFST interface database considering long-term effects was established and the mechanism of long-term effects have been revealed. As the duration increases, the bond stress decreases at the beginning, and thereafter stabilizes where the friction component dominates. Compared to that without interfacial load, long-term interfacial load accelerates the damage to chemical adhesion and micro-interlocking at initial stage, but the difference of their effects on bond stress is not significant in the later stage. On this basis, a long-term interfacial constitutive model for its full-lifecycle safe design and a simplified numerical method for long-term effects on bond behavior have been proposed.

Unsuppressed HIV Viral Load and Related Factors in Patients Receiving Antiretroviral Treatment in Tanganyika Province, Democratic Republic of Congo (DRC)

Antiretroviral treatment (ART) has revolutionized the management of the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS), enabling long-term viral load (VL) suppression in patients. Despite the proven effectiveness of ART, a significant proportion of patients with HIV receiving ART fail to achieve viral load suppression (VLS). This study aimed to identify factors associated with low VLS in the Tanganyika province. An unmatched case–control study was conducted from January 2022 to June 2023, including 22 care facilities with viral load data. Data were collected from patient records. For each reviewed record, the patient was invited for an interview upon providing informed consent. Data were analyzed using SPSS version 27. In a multivariable binary logistic regression model, variables with a p-value &lt; 0.05 and a 95% confidence interval for the adjusted odds ratio were considered significantly associated with unsuppressed VL. A total of 462 individuals, including 156 cases and 306 controls, were included in the study. The mean age (standard deviation) of participants was 42.12 (±11.6) years. The following covariates were significantly associated with unsuppressed VL: poor HIV status disclosure to a confidant [adjusted OR = 2.10, 95% CI (1.33–3.31), p = 0.001], poor ART adherence [adjusted OR = 2.01, 95% CI (1.25–3.23), p = 0.004], ART interruption [adjusted OR = 3.43, 95% CI (2.00–5.88), p &lt; 0.001], no participation in support groups [adjusted OR = 2.16, 95% CI (1.25–3.71), p = 0.005], baseline WHO clinical stage 3 and 4 [adjusted OR = 2.24, 95% CI (1.32–3.79), p = 0.003], opportunistic infections (OIs) [adjusted OR = 2.30, 95% CI (1.27–4.16), p = 0.006], and non-communicable chronic diseases (NCDs) [adjusted OR = 2.30, 95% CI (1.10–4.79), p = 0.026]. Given the clear association between several factors and unsuppressed VL, prevention should involve the implementation of innovative strategies targeting at-risk patient groups. Strengthening the monitoring of these factors among active patients at each appointment is recommended to achieve this goal.

Thermo-mechanical coupling failure mechanisms of reusable SiCf/SiC composites with PyC interphase

The extreme and repeated aerothermal environments working on reusable launch vehicles bring challenges for the design of hot structure. Due to the outstanding high-temperature resistant, SiCf/SiC composite is an excellent candidate material for hot structures in re-entry vehicles. In this paper, the thermo-mechanical coupling failure mechanisms of SiCf/SiC composite are investigated comprehensively. Experimental results reveal different failure mechanisms of SiCf/SiC composites subjected to monotonic quasi-static tension at room temperature and high temperature, cyclic thermal fatigue and thermo-mechanical coupling fatigue. Cyclic thermal environment causing oxidation of interphase layer and embrittlement of fiber plays a significant role in decrease of load bearing capacity of SiCf/SiC composites. The long-term periodic fatigue load that is superimposed on the cyclic thermal condition would further deteriorate the performance of materials. To better understand the damage evolution process, a thermo-mechanical coupling fatigue model is proposed to describe the degradation of SiCf/SiC composites for different stress levels. The service life of SiCf/SiC composites is obtained, which could be used to evaluate the reusable performance of SiCf/SiC hot structure. The results of this study provide novel insights into the design of SiCf/SiC composites for reusable launch vehicles under prolonged and repeated service environment.

Tetris: Proactive Container Scheduling for Long-Term Load Balancing in Shared Clusters

<i>Tetris:</i> Proactive Container Scheduling for Long-Term Load Balancing in Shared Clusters

Fatigue life prediction of cracked cross beam of mining linear vibrating screen under cyclic load

The cross beam of a mining linear vibrating screen is prone to cracking under long-term cyclic load. In order to accurately predict the fatigue life of the cracked cross beam, a coupled analysis method of vibration and crack propagation is proposed. A 2D dynamic model of the vibrating screen is established based on the finite element method, which is verified by the vibration test platform. The cracked Euler beam element is used to model the cracked cross beam. The effects of crack depth, amplitude of excitation force, frequency of excitation force, and crack location on the crack-tip stress intensity factor of the cracked cross beam are investigated in detail. In addition, an iterative method is proposed on the basis of the Paris model. The residual service life of the beam under different frequencies of excitation force, amplitudes of excitation force, spring stiffness, crack positions, and degrees of stiffness imbalance are discussed. The results demonstrate that the fatigue life of the beam increases as the frequency of excitation force and spring stiffness increase. The increase of the amplitude of excitation force and spring permanent deformation reduces the fatigue life. The conclusion obtained provide some theoretical guidance for the design and routine maintenance of mining linear vibrating screens.

Long-Term Permissible Load Currents of Single-Core Cables with a Voltage of 10 kV with Cross-Linked Polyethylene Insulation of Various Designs

Long-Term Permissible Load Currents of Single-Core Cables with a Voltage of 10 kV with Cross-Linked Polyethylene Insulation of Various Designs

Non-linear mechanical behaviour of thermoplastic elastomeric materials and its vulcanizate under tension/tension fatigue deformation by fourier transform rheological studies

Fourier transform (FT) rheology opens up novel frontiers in understanding non-linear mechanical behaviours of polymeric materials under sustained long-term dynamic load. The prediction of the exact point of appearance of a crack in a sample under dynamic mechanical strains of large amplitude and the fatigue analysis has been made possible to such degrees of precision, previously not possible through conventional rheological and mechanical analysis. In this work, the fatigue behaviour of a thermoplastic elastomeric material (TPE) and a thermoplastic vulcanizate (TPV) from thermoplastic polyurethane (TPU) and epichlorohydrin− ethylene oxide−allyl glycidyl ether (GECO) rubber is investigated by Fourier transform studies under oscillatory strain-controlled tensional test to understand the linear and non-linear mechanical behaviour. Fatigue analysis is performed through the fingerprint harmonics of the material’s stress response, i.e., the second and third harmonics, ( I 2/1 and I 3/1) to establish the stress nonlinearity, asymmetry, and the formation of macrocracks. Furthermore, these higher harmonics are fitted with the Neo-Hooke and Mooney-Rivlin model to fundamentally understand the mode of fatigue failure, and a close agreement between theoretical fitting and experimental outcomes is established. Strain-life curves were utilized for the thorough investigation of the fatigue behaviour of the specimens and more than 9-fold enhancement in the strain life of the TPV is observed over TPU at a strain amplitude of ∼1.05 indicating an increasing ductility. Finally, the necessity of FT rheology was further emphasised as it is observed that I 2/1 and I 3/1 harmonics are more sensitive towards fatigue response as compared to the storage modulus and the complex modulus. Henceforth, the FT rheology analysis has enabled the current study to efficiently establish the ductility of each individual specimens and for prediction of the dynamic service lifetime of the developed materials.