Speed Load Research Articles

Co-optimization of power and spinning reserve in multi-area electrical networks with wind farms

Integrating wind farms into electrical networks reconfigures energy matrices and poses new challenges to system operators. For instance, wind farm owners must now guarantee spinning reserves stipulated in grid codes. This prompts an urgent quest for optimizing power and reserve allocation in liberalized markets using advanced models. In this sense, this paper introduces an optimal power flow (OPF) model to co-optimize power and spinning reserve in multi-area electrical networks with wind farms. The granularity and layout of the wind plant are considered for a correct calculation of the spinning reserve in each variable speed wind turbine. Unlike classical OPF studies, where generator participation is free and mandatory in system reserves, this new approach considers both power and reserve as variable factors in the optimization process, which depend on reserve costs, system load, and wind speed. The approach is evaluated through comparative analyzes on two power networks: a small 12-bus, two-area network with two wind farms and a larger 100-bus, four-area network with four wind farms. Multi-period 12-hour look-ahead analyzes are conducted with variable conditions of demand and wind speed. The studies demonstrate the advantages of the new model compared to the classical OPF, showcasing its ability to optimize power dispatch with wind farms actively contributing to the spinning reserve requirements of the power network.

Fatigue life of RC bridge decks affected by speed and load weight of wheel-type moving loads

Over the service life of a bridge, vehicles vary in terms of speed and load weight, leading to varying degrees of fatigue damage. Particularly under wet condition, the fatigue life of reinforced concrete (RC) bridge decks experiences a significant decline. In this study, the results of fatigue life of RC bridge decks are systematically calculated for under wheel-type moving loads with various speed and load weight according to practical situation of bridges in both dry and wet condition by an acceptable approach involves a multi-scale and multi-chemo–physics analysis system (DuCOM-COM3) that incorporates the water-crack interaction. The results indicate that the effect of speed on fatigue life is not significant and follows a complex pattern, and the effect of load weight on fatigue life is dominant, with a heightened sensitivity to load weight variations under wet condition. Based on the simulation results of fatigue life, calculation formulations for fatigue life are presented accurately for dry and wet condition respectively, considering both load weight and speed as parameters, with the determination coefficients R2 are 0.977 and 0.952, respectively. In addition, a predictive method for the service life under constant environmental condition is proposed based on the Palmgren-Miner’s linear rule, and a case analysis is conducted by utilizing practical traffic flow data monitored by a piezoelectric-based dynamic weigh-in-motion system set on Jiashao Bridge, showing that the service life under dry condition is 55.41 years, while that under wet condition reduces to 1.03 years. Finally, a comprehensive service life predictive method considering actual and alternating environmental conditions is proposed.

A novel modified artificial rabbit optimization for stochastic energy management of a grid-connected microgrid: A case study in China

The energy management (EM) solution of the microgrids (MGs) is a crucial task to attain most economic, reliable and sustainable operation state of the MGs. This paper aims to solve the optimal scheduling and stochastic EM problem of a smart MG without and with demand side response (DSR) including MT, FC, PV, WT, and a battery storage system (BSS). A study case in Wenzhou city of China is conducted to reduce the operation cost and maximize the utilization of renewable energy. The system uncertainties like loading, temperature, solar irradiance and wind speed are considered which were obtained from real meteorological data. The normal, lognormal, Weibull PDFs as well as Monte-Carlo and RBS methods are used for uncertainty modelling. A modified artificial rabbit optimization (MARO) is proposed for EM solution based on three strategies including fitness-distance balance, exploitation mechanism of PDO and quasi-opposite-based learning (QOBL) to boost exploration and exploitation phases of traditional ARO. The statistical and non-parametric tests are applied via benchmark functions to validate the performance of MARO. As per the obtained results, the MARO is superior for EM solution compared to other techniques and the operation cost is reduced from 252.0721€ct/day to 184.8435€ct/day with saving of 26.86 % considerably with application of DSR.

Analysis of the Influence of Velocity Effect on the Indirect Tensile Strength Test Results of Asphalt Concrete

The asphalt mixture AC-20C was compacted by standard method, and the physical and mechanical properties of asphalt concrete specimens were tested. In the test process, the difference of indirect tensile strength is investigated by using different loading rates, so as to evaluate the correlation between the test process and the test results of asphalt mix-ture. The test results show that: when the appropriate loading speed is adopted, the asphalt mixture test can achieve more ideal test results, and different test conditions will produce completely different results, so that the test data are completely distorted. Under the condition of excluding other factors, more real test data can be obtained, so the test should be carried out in strict accordance with the requirements of the specification.

Tribological properties of ternary heterojunction nanocomposites with MoS2 as the main body are enhanced

g-C3N4 has a strong C-N covalent bond within the monolayer and a weak van der Waals force between the lamels, which enables it to have similar lubrication properties to other two-dimensional layered materials. In this study, a new type of g-C3N4/MoS2/ZnS heterogeneous nanocomposites was prepared by a one-step hydrothermal method XRD, SEM, FI-IR, and other methods were used to systematically study it. Furthermore, a ball-on-disk tribometer extensively examined the tribological behavior of g-C3N4/MoS2/ZnS heterojunction in pure oil. The relationship between applied load and rotational speed on performance is also revealed. Compared with g-C3N4 and g-C3N4/MoS2 nanocomposites, g-C3N4/MoS2/ZnS has better frictional properties. It is worth noting that when g-C3N4/MoS2/ZnS is in the base oil mass ratio at 1.0 wt.%, the friction coefficient is reduced by 49%. In addition, g-C3N4/MoS2/ZnS ternary heterojunction exhibits better tribological properties than g-C3N4/MoS2/ZnS mixture, expanding their practical applications in industry and agriculture.

In-Plane crushing performance of bionic glass Sponge-Type honeycomb structures

Honeycomb structures are commonly adopted due to their superior energy absorption capacity. In this study, a new bionic glass sponge–type honeycomb structure (BSH) with a quadrilateral octagonal mesh microstructure inspired by the sea sponge structure was proposed. The in-plane crushing performance of the BSH with different geometrical parameters under different crushing speeds was investigated by ABAQUS/Explicit. The numerical findings suggested that the BSH displayed stronger energy absorption in contrast to the square, hexagonal and hierarchical honeycombs at both quasi-static and dynamic crushing conditions. More plastic hinges and more unit walls involved in deformation resulted in a high energy absorption capacity. In addition, three typical deformation modes of the BSH under different loading speeds were discussed, and the empirical model to predict the plateau stress of the BSH was established based on the shock wave theory. Finally, the effect of boundary segmentation parameter m on crushing performance was also illustrated. The energy absorption capacity reaches a maximum at m = 3 for quasi–static loading, whereas at m = 5 for dynamic loading. These findings provide valuable insights into the optimization of bionic honeycombs.

Effect of bearing size on film thickness in grease-lubricated axially loaded deep groove ball bearings

Estimating the film thickness in a grease lubricated bearing in the post-churning phase is complex because of the prevalent starved lubrication conditions. In our earlier work, we showed that the relative film thickness (hg/hff) in an axially loaded 6209 deep groove ball bearing (DGBB) depends on the product of viscosity, load and linear speed (ηbu). In this article, we present the results of experiments performed using bearings of different sizes – 6204, 6206, 6209 – and show that the relative film thickness maintains a power-law relationship with ηbu, independent of the bearing size.

Integrated Parameter Identification Based on a Topological Structure for Servo Resonance Suppression

In the dual-inertia servo system, the servo resonance in which the characteristics are closely related to the mechanical parameters is usually suppressed by adding a notch filter. As a result, accurate mechanical parameter identification facilitates adjusting the notch parameters and avoiding the failed servo resonance suppression caused by the mechanical parameter mismatch. In this paper, a topological structure expanded by five improved Sliding-Mode Observers (ISMOs) is proposed to simultaneously identify the load speed, the motor inertia, the load inertia, the stiffness coefficient, and the load disturbance, where the load speed and the load disturbance are considered as intermediate variables to provide sufficient load-side information to ensure the identification accuracy of the mechanical parameters. Furthermore, according to the natural knowledge of the dual-inertia servo system, a time-varying interconnected gain with an equal derivative to the identification parameter in each ISMO is designed to promote the global convergence of the topological structure. Finally, the identified mechanical parameters are utilized to adjust the notch parameters for the servo resonance suppression. Simulation and experimental results are presented to indicate the superiority of the topological structure and the effectiveness of the servo resonance suppression.

ANTHROPOMETRIC AND PHYSICAL QUALITIES OF SEMI-PROFESSIONAL RUGBY LEAGUE PLAYERS

AIM The aim of the current study was to investigate the physiological and anthropometric characteristics of semi-professional rugby league players across a typical season, including pre- and post-season data. METHODS Thirty-five semi-professional rugby league players, mean age 25.38 ± 2.35 years were measured for height, body mass, sum of skinfolds, and speed (20m sprint). Global positioning system (GPS) data, sampling at 10 Hz, were collected, two pre-season and eighteen Queensland Cup rugby league matches in the 2023 season for 10 players (backs and forwards). Data was categorized into total distance (km), sprint distance (m), power plays, energy expenditure (kcal), player load, and top speed (m/s). RESULTS Compared with forwards the backs had significantly lower body mass (99.4kg vs 90.8kg), and significantly greater speed during 20m sprint (3.00 vs 3.1sec). Sum of skinfolds, no differences between backs and forwards across the three time points, 104.2 vs 106.2mm, 103.9 vs 110.9mm and 93.8 vs 108.1mm. Reviewing the GPS data across the trial and cup games revealed a number of significant differences between backs and forwards, backs greater overall distance (6.63km vs 5.26km), sprint distance (467.53 vs 264.63m), power plays (37 vs 25), energy expenditure (1002.42 vs 778.90 kcal), player load (311.50 vs 275.16), top speed (8.02 vs 7.02m/s). CONCLUSION Retrospective analysis of our data has allowed us to understand the activity demands between match types and differences in activity demands between seasonal phases of training in semi-professional male rugby league players and will permit further specificity of training and improve performance. Determining the fitness and physiological profiles and how they relate to training and match demands will allow the coaching staff to develop more targeted training strategies in order to optimally develop the fitness characteristics that predominantly underpin match demands.

Experimental development and validation of tribological run-in strategies to reduce friction in hydraulic applications

A particularly demanding contact in axial piston pumps is the one between cylinder block and valve plate. The tribological behavior of the contact can be changed by a run-in process. Publications on fast and efficient run-in are rare as this knowledge is often considered confidential. For this paper, tests have been carried out on a disc-on-disc tribometer to examine the run-in behavior of a material pairing and to identify suitable parameters for run-in. A methodology has been developed which can be used to find the optimal normal load and rotational speed for the run-in process to shorten the run-in time significantly.

Hot-press sintering of SiC whisker reinforced TiB2-B4C composites and its mechanical property characterizations

TiB2-B4C composites modified by SiCW with excellent mechanical properties were prepared using hot-press sintering. The effects of SiCW content on the microstructure, densification behavior and mechanical properties were investigated. The dynamic failure behavior was analyzed through the Hopkinson Bar (SHPB) testing. The results demonstrate that the addition of SiCW can effectively refine the microstructure and simultaneously improve the mechanical properties. The TiB2-B4C composite renforced with 6 wt% SiCW exhibits a nearly full-dense microstructure and excellent mechanical properties. The relative density, flexural strength, Vickers hardness and fracture toughness can reach to 99.95 %, 724 ± 61 MPa, 19.8 ± 0.7 GPa and 6.7 ± 0.3 MPa m1/2, respectively. The dynamic failure behavior exhibits that the damage degree increases with elevated loading speed. Moreover, the single-peak and double-peak of the waveform correspond to the two damage degrees of "broken" and "crushed".

Research on the Support Performance of Internal Feedback Hydrostatic Thrust and Journal Bearing Considering Load Effect

This study aims to analyze the impact of uniform and eccentric load conditions on the performance of internal feedback hydrostatic thrust and journal bearing. Two distinct models are established: a three-degrees-of-freedom uniform load model and a five-degrees-of-freedom eccentric load model. The support stiffness, overturning stiffness, and flow rate for both thrust and journal bearings are calculated. Additionally, numerical analysis is conducted to examine the influence of oil film thickness, inlet pressure, and restrictor size on the operational characteristics of the bearings, revealing the interplay between an eccentric load and journal bearing speed. The validity of the theoretical algorithm is verified through finite element simulation. The research outcomes hold significant guiding implications for the design and application of internal feedback hydrostatic bearings.

Progressive damage analysis of embedment of metal washer into timber

ABSTRACT Metal washers are widely used in joints of timber structures. Thick washers embed fully into timber, whereas thin washers partially embed into timber due to their bending deformation. For thick washers, physical models have been proposed to estimate the stiffness and strength of timber. However, for thin washers, these estimation methods are insufficient. The objective of this study is to propose a finite-element analysis (FEA)-based approach to predict the stiffness and strength of wood during washer embedding, as well as forecast plasticity and damage behaviours of timber, regardless of the washer size. The FEA used a constitutive model with plastic and damage criteria for timber. In the FEA, an explicit dynamic solution method was used to prevent solution divergence. The FEA reproduced the embedment load–displacement relation and damage behaviours of three species. In addition, the FEA predicted the initial stiffness, second stiffness, and yield load with error margins of 12%, 16%, and 7%, respectively. The influences of the loading speed and mesh fineness on the FEA were investigated numerically to validate the results. In addition, parametric studies on contact stiffness and damage constants were conducted to understand the influences of material constants on the embedment behaviours of FE models.

Optimization of wear parameters for ECAP-processed ZK30 alloy using response surface and machine learning approaches: a comparative study

The present research applies different statistical analysis and machine learning (ML) approaches to predict and optimize the processing parameters on the wear behavior of ZK30 alloy processed through equal channel angular pressing (ECAP) technique. Firstly, The ECAPed ZK30 billets have been examined at as-annealed (AA), 1-pass, and 4-passes of route Bc (4Bc). Then, the wear output responses in terms of volume loss (VL) and coefficient of friction (COF) have been experimentally investigated by varying load pressure (P) and speed (V) using design of experiments (DOE). In the second step, statistical analysis of variance (ANOVA), 3D response surface plots, and ML have been employed to predict the output responses. Subsequently, genetic algorithm (GA), hybrid DOE–GA, and multi-objective genetic algorithm techniques have been used to optimize the input variables. The experimental results of ECAP process reveal a significant reduction in the average grain size by 92.7% as it processed through 4Bc compared to AA counterpart. Furthermore, 4Bc exhibited a significant improvement in the VL by 99.8% compared to AA counterpart. Both regression and ML prediction models establish a significant correlation between the projected and the actual data, indicating that the experimental and predicted values agreed exceptionally well. The minimal VL at different ECAP passes was obtained at the highest condition of the wear test. Also, the minimal COF for all ECAP passes was obtained at maximum wear load. However, the optimal speed in the wear process decreased with the number of billets passes for minimum COF. The validation of predicted ML models and VL regression under different wear conditions have an accuracy range of 70–99.7%, respectively.

Overview of the Influence of Static Water Saturation on The Mechanical Properties of Concrete

This paper reviews a series of experimental and theoretical research results on the influence of existing pore water on the static and dynamic properties of concrete. This paper summarizes the current experimental research methods and conclusions, analyzes the influence mechanism of moisture content and loading speed on the elastic modulus and strength of concrete, and points out that the influence of pore water on concrete properties should be the result of the joint action of multiple factors.

The effect of loading rate on mixed mode I/II fracture behavior of adhesively bonded joints: Experimental and numerical approach

In this study, the use of a modified Arcan fixture to investigate the fracture behavior of adhesively bonded Al/Al joints has been discussed under rate-dependent loading in various loading conditions (mode I, mode II, and mixed mode (I/II)). It was observed that the testing speed has a significant effect on the fracture properties of the joints, especially in pure mode, II. The results indicated that failure load was increased for all three loading modes and an increase was also observed for strain energy release rate at all loading conditions. The critical fracture loads obtained from the experimental tests were used to calculate the values of the critical stress intensity factors and strain energy release rates for loading modes I, II, and mixed mode I/II at different loading rates by using the finite element method. It was shown that the values of strain energy release rate for loading mode II were higher than mode I and mixed mode at all loading speeds. Finally, scanning electron microscope analyses (SEM) were used to investigate the effects of loading speed on the failure surfaces of the adhesive in microstructural scales and it was shown that at low loading rates, the number of crazes that cause failure in the adhesive layer increases.

Influence Factors of Powerline Communication by Artificial Intelligence Approach based on Rock Electric Signal

The field of powerline communication (PLC) has been around for more than a century and uses the power line as a means of information transport. Because it utilizes the current system to transfer data using electrical power, it is advantageous because it prevents the need for new installations. The impact of coal and rock electric signals is examined using the established test methodology, taking into account the coal and rock temperature, characteristics, friction, loading speed, and load size. The main findings can be summed up as follows: Depending on the intensity of the electrical signals produced, the change rule of electrical signals in the coal rock rising with temperature can be separated into three stages. The electrical signals produced by the uniaxial compression of coal-rock mass with varying properties have distinctly different amplitudes. The friction between coal and rock can produce electrical impulses. As loading speed increases, the electrical signal that indicates when the coal rock is prepared to fracture tends to get stronger. The information bottleneck perspective is then used to study information theory and artificial intelligence. In conclusion, we go through a few concepts about the deep integration of AI methods with wireless communication networks. The fundamental aspects of AI that are pertinent to various uses have been briefly addressed at the outset of the paper.

Effect of operating conditions and surface roughness on grease lubrication efficiency

The aim of this paper is to investigate the effect of operating parameters (load and rotational speed) and arithmetic mean deviation (Ra) roughness value on temperature rise and tribological behavior of greased point contact under heavy load. The 3-factor, 4-level orthogonal friction experiments are designed and carried out. The moving point heat source integration method is applied to calculate the transient temperature rise of interfaces. The results show that the case with load 1900 N, rotational speed 260 rpm and Ra 0.4 μm has the highest friction coefficient and temperature rise. The grease fails and layered spalling and oxidative wear occur on the wear scar. Four second-order regression models are established to predict friction coefficient and the maximum temperature rise under different load, rotational speed and surface roughness. And the determination coefficients R2 of them are higher than 97 %. The models are helpful to determine if the working conditions fall within effective lubrication range and avoid severe damage.

Experimental and simulation investigation for prismatic lithium-ion battery cells under impact loading

In the current work, prismatic lithium-ion battery (LIB) cells were impacted in various rigid cylinder loading speeds (v = 1, 5, 10, 2000 and 5000 mm/s), which provided the data basis for establishing a practical and reasonable LIB cell damage assessment method. Based on thermal-runaway cell safety borders (TCSB) and undamaged cell safe borders (UCSB), the deformed cells can be classified into safe, risk and failure regions. With the increment of the v values, the UCSB and TCSB of cells decreased linearly along a logarithm axis. Moreover, the relationships between key cell parameters (cell thickness, separator thickness and separator fracture strain) and the cell deformation limits (DL) under rigid cylinder impact loads were also revealed. A DL prediction method was newly introduced for the prismatic LIB cells with different sizes. Finally, the tensile mechanical data of cell components (anodes, cathodes and separators) were also measured for cell local detailed simulation models. By the simulations, the effect of the frictional behaviors between cell components on the deformation processes and failure mechanisms of LIB cells were deeply discussed.

Effect of adhesive thickness and loading speed on bonding strength in single-lap adhesive joints with aluminum 5754-H111

This study provides shear test results of single-lap adhesive joints with aluminum 5754-H111. To investigate the effect of adhesive thickness on joint strength in single-lap adhesive joints, three different thicknesses (0.2, 1, and 2 mm) were applied. Increasing the adhesive thickness from 0.2 mm to 1 mm and from 0.2 mm to 2 mm resulted in a reduction in shear load of roughly 36% and 44%, respectively. It has been observed that the joint strength decreases with increasing adhesive thickness in single-lap adhesive joints with aluminum 5754-H111. In addition, single-lap adhesive joints were tested at various loading rates (1, 10, and 100 mm/min), and the influence of loading speed on adhesive strength was studied. The shear load increased with the loading speed in the test results of single-lap adhesive joints.