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The relationship between repetitive motion and level of fatigue among weaver craftsman

Background: The weaving process is a repetitive activity because of the repetitive hand movement pattern with a load period of < 3 kg. Work patterns that do not pay attention to ergonomics will cause problems such as fatigue, injury, musculoskeletal disorders, work accidents, and issues due to excessive repetitive motion. This study aimed to determine the relationship of repetitive motion to the level of fatigue in weaving workers.
 Methods: This study used a cross-sectional approach using a sample of 44 weaving artisans who joined the association in the Special Region of Yogyakarta. This study used non-parametric statistical tests with Kendall Tau correlation test techniques.
 Results: Based on data analysis in the study, a positive correlation was obtained with a significance value of p= 0.001 (p< 0.05), which means a significant positive correlation exists between repetitive motion and fatigue level in weaving workers.
 Conclusion: Based on the results of research and discussion, it can be concluded that there is a relationship between repetitive motion and fatigue in weaving artisans in the Special Region of Yogyakarta. It is also proven by the Kendals Tau test, which has a p-value = 0.001 or p< 0.050, so it can be said that there is a relationship between repetitive motion and fatigue in weaving artisans in Yogyakarta.

Asymptomatic Autonomic Dysregulation after Recovery from Mild COVID-19 Infection Revealed by Analysis of Heart Rate Variability Responses to Task Load.

(1) Background: The coronavirus disease 2019 (COVID-19) infection is often followed by various complications, which can cause disturbances in daily life after recovery from the infectious state, although etiological mechanisms are not fully elucidated. Previous studies have indicated that autonomic dysregulation is an underlying factor, and it is of interest to clarify whether autonomic dysregulation is also present in the asymptomatic subjects after COVID-19 infection (post-COVID-19) for early detection of post-COVID-19 complications. (2) Methods: In the present study, autonomic activity was assessed using heart rate variability (HRV) analysis in the workers who recovered from mild COVID-19 infection (n = 39). They took a leave of absence for an average of 11.9 days and returned to the original work without complications. HRV was measured after an average of 9.3 days from return. High-frequency (HF) and low-frequency (LF) HRV parameters and heart rate (HR) were recorded during a three-behavioral-state paradigm of approximately 5 min length composed of initial rest, task load, and post-task rest periods and were compared with the data of the workers without the history of COVID-19 infection (normal, n = 38). (3) Results: The HRV and HR scores at the initial rest in the post-COVID-19 subjects showed no difference from those in the control. It is found that the post-COVID-19 subjects exhibited an attenuation of LF/HF increment during the task load and an excessive increase of HF together with a decrease of LF, LF/HF and HR during the post-task rest period in comparison with the initial rest scores. (4) Conclusions: These abnormalities are evaluated as asymptomatic autonomic dysregulation in response to task load, are frequently present after COVID-19 infection, and could be related to the generation of complications.

Modern methods of physical rehabilitation for the prevention of osteochondrosis in sports players

An important component in increasing the efficiency of the training process and achieving the highest possible results of athletes - players are the methods of physical rehabilitation in osteochondrosis, which are aimed at rapid recovery of the body and are an integral part in the development of training programs. Therapeutic physical culture, massage and physiotherapeutic methods used in the prevention of osteochondrosis are considered. Taking into account the methods and means of physical rehabilitation in athletes with osteochondrosis is a priority direction in the correction of loads in different periods of the annual cycle.
 The scientific novelty of the study is due to the fact that osteochondrosis of the spine in athletes is one of the most common chronic diseases. During the training and competitive process, athletes-players endure heavy loads, which provoke further exacerbation of the manifestations of osteochondrosis, where their physical and functional capabilities in motor activity are significantly limited. Therefore, it becomes obvious the need to consider modern methods and programs of physical rehabilitation as a comprehensive approach used in the prevention of osteochondrosis.
 However, in recent years, the specifics of the physical rehabilitation of osteochondrosis of the spine in athletes - highly qualified players have been caused by a number of contradictions. In particular, the issue of the impact of spinal cord pathology on the motor functions of athletes has not been investigated. The effectiveness of the use of rehabilitation programs of physical rehabilitation, which open up new possibilities for the prevention of osteochondrosis, has not been highlighted.

Study on the synergistic regulation strategy of load range and electrolysis efficiency of 250 kW alkaline electrolysis system under high-dynamic operation conditions

Alkaline water electrolysis (AWE) has the highest technological maturity among all the water electrolysis technologies for hydrogen production, however, reducing the minimum load boundary and improving the electrolysis efficiency are the technical challenges of the AWE system that still exist and urgently require optimization. The minimum load is primarily limited by the hydrogen to oxygen (HTO) from cross-diaphragm transfer and lye mixing, with HTO above 2.0% being a significant safety risk. Reducing the lye flow rate and pressure are effective while two of the few ways by regulating the operating parameters to improve the HTO thus extend the minimum load boundary, but will worsen electrolysis efficiency. Therefore, this study proposes a synergistic regulation strategy of pressure and lye flow rate: maximizing pressure and lye flow rate during high load period to ensure high electrolysis efficiency; adjusting lye flow rate and pressure during medium load period to ensure HTO≤2.0% and maximize the electrolysis efficiency; and reducing lye flow rate and pressure to a low level during the low load period to broaden the minimum load so as to improve overall efficiency of AWE system when loading with fluctuant green electric. This work elaborates the HTO routes, influencing factors and parameter optimization mechanism by building a system-level steady-state and dynamic gas purity model. The optimal combination curve of pressure and lye flow rate is obtained and its control effect on performance parameters, in terms of minimum load, system energy consumption, energy utilization, electrolysis efficiency and so on, is compared and verified in high dynamic wind and photovoltaic (PV) power scenarios. Finally, the optimal wind & PV power ratios are explored based on the optimal operation curve, which will provide a reference for the future large-scale development of hydrogen production scenarios direct-coupled with wind and PV power. The minimum load is extended from 42.0% in the lye flow rate alone control to 21.2% in the pressure alone control and finally to 15.6% in the lye flow rate and pressure synergistic control method. In the absence of electrical replenishment, wind and PV energy utilization efficiency can reach up to 98.3% and 95.6%, respectively.

The effect of varying stress intervals on fatigue of rock salt

The surrounding rock of underground energy storage salt caverns is subjected to periodic loading with stress intervals during actual operation. To study the fatigue behavior of rock salt with such stress intervals, one conventional fatigue test and three fatigue tests with multi-step varying stress intervals (MVSIs) were conducted. The results show that the circumferential deformation first decreases and eventually becomes similar to the axial deformation in fatigue tests with MVSIs, as the interval duration increases. Both the dissipated energy and the spacing between the loading and unloading curves of a single cycle first decreased, then remained constant, and finally increased sharply as the stress interval increased. When the stress intervals corresponded to the elastic phase of loading (between 20% and 40% of the uniaxial compressive strength), the rock salt was subjected to the minimum damage. Based on the Bauschinger effect and dislocation internal friction theory, the micromechanism of rock salt fatigue was further explained.

Исследование усталостного старения изоляции тяговых электродвигателей тепловозов при циклической нагрузке

Purpose: To analyze the processes of fatigue aging of the insulation of traction electric machines of locomotives under cyclic loads in operation. Methods: When solving typical problems of fatigue strength of insulating materials of electric locomotives, periodic loading cycles are used in the study. Results: The analysis of the processes of fatigue aging of insulation materials of electrical machines shows that the main parameters that increase the intensity of aging are the frequency and amplitude of the heating cycle. Thermomechanical stresses increase with rise of heating speed and temperature amplitude. Practical significance: Determination of the fatigue characteristics of the insulation material is very important when modeling its damage, which will increase the reliability of electric machines of modern locomotives at the stages of design, manufacture, modernization and operation.

Effect of abutment type and creep behavior on the mechanical properties of implant restorations in the anterior region: A finite element analysis.

This study aimed to assess the effect of abutment variation and creep on dental implant restorations. Three finite element analysis (FEA) models of implant restorations were created, which were restored by conventional one-piece abutment (CA), hybrid abutment crown (HAC), and multi-unit abutment (MUA). The contacts were considered intimate (no friction), except for implant/abutment, abutment/screw, and abutment/screw/crown (HAC) attachments. The related mechanical parameters were used to improve the authenticity of the study. Instantaneous loads and constant loads (100 s) of 130 N were applied at a 30° angle to the palatal portion of the crown. Results were qualitatively and quantitatively evaluated using the equivalent von Mises stress, micro-gap distance of the implant-abutment interface (IAI), preload changes, and safety index. The stress state of each component differed depending on the restoration type, from CA and HAC to MUA. Implants and screws were the structures that suffered the most stress under instantaneous loads. Each metal structure exhibited a substantial decrease in stress during a constant loading period. The screws of the MUA abutment showed more preload loss (62.1 N) after constant loads for 100 s. MUA base produced less micro-gap (0.72 μm) at the IAI when it was compared with the CA group (0.93 μm) and HAC group (3.29 μm). The abutment type influences the mechanical properties and performance of implant restorations. The creep effect decreases the maximum stress level and increases the safety factors of each structure, indicating that stress-related mechanical complications may not occur more easily.

Investigation on Aerodynamic Fluid–Structure Coupling Vibration of 160 km/h EMU Tail in Single-Track Tunnels

Recently, the phenomenon of tail-sustained swaying of the 160[Formula: see text]km/h EMU in single-track tunnels has gained much attention, especially for the rear-powered vehicle. This phenomenon is investigated from the perspective of aerodynamic fluid–structure coupling vibration in this study. The aerodynamics simulation model of the train in tunnels and the multi-body dynamics model of the rear-powered vehicle were respectively established through the software of XFlow and Simpack, and then the fluid–structure coupling vibration was simulated by using real-time data dynamic exchange between the two models. Moreover, the carbody’s vibration acceleration and the aerodynamic loads acting on the carbody under various wheel–rail contact geometrical conditions were discussed. Finally, the train tail swaying in field was tested, and the dominant frequencies were analyzed. The results show that the periodic aerodynamic loads and the frequency locking effect caused by the coupled vibration are the main factors for ride comfort deterioration. The violent vibration caused by fluid–structure coupling is named vortex-induced vibration (VIV) in some industries such as bridge and submarine pipeline. For the vehicle in this work, with the decrease of equivalent conicity in wheel–rail contact, the amplitude of carbody swaying increases owing to the carbody hunting, which enhances the fluid–structure coupling vibration, and further deteriorates the ride comfort. The swaying of the carbody is dominated by the vehicle hunting frequency, and the improvement of vehicle lateral stability can weaken this phenomenon.

A Bi-level optimization strategy for electric vehicle retailers based on robust pricing and hybrid demand response

The high penetration of electric vehicles (EVs) poses both opportunities and challenges for power systems. EV retailers, playing a critical role in the demand response mechanism, face market risks caused by uncertainties in electricity consumption and prices. To address the operational issues of large-scale EVs and tap the potential of EV retailers, a temporal and spatial domain-based optimization strategy is proposed, which is implemented on bi-level (referring to transmission and distribution grid networks). First, a physical scheduling model of the grid is established, consisting of a novel hybrid demand response mechanism considering the incentives of EV retailers and the retail electricity price of EV users, and a new robust retail electricity pricing strategy handling the uncertainties of EV behavior and the electric market. Then, a bi-level optimization strategy is presented: at the upper level, in the transmission network, based on the robust pricing strategy, a unit commitment model that coordinates the hybrid demand response with other distributed energy resources is designed to optimize load periods of EVs in the time domain; at the lower level, in the distribution network, an optimal power flow model is proposed to spatially dispatch the location of EV loads. The impacts of retail price profile, EV penetration, hybrid demand response mechanism, and EV load location are analyzed in ten tests using the IEEE 33 distribution network. Simulation results indicate that the robust pricing strategy can effectively handle uncertainties, the integration of the hybrid demand response mechanism into scheduling can ensure the benefits of all participants, and the bi-level optimization strategy can accommodate distributed energy resources temporally and spatially.

A Fuzzy-Based Proportional–Integral–Derivative with Space-Vector Control and Direct Thrust Control for a Linear Induction Motor

In this study, the analysis and control of a multi-phase linear induction motor loaded with a variable mechanical system are carried out. Mathematical models are established, and simulation results are analyzed for an improved proportional–integral–derivative controller with closed-loop vector control for PLIM. To make the PID controller more responsive to load thrust disturbances, a fuzzy PID load thrust observer was developed. The FPID is similarly based on space-vector modulation DTC technology to regulate the PLIM’s speed, flux, and thrust. The FPID output is used to calculate the reference thrust force, which is compared to the actual thrust value to calculate the second error. To maintain the linear speed of the PLIM at the specified reference values and at different load values, the FPID controller settings are adjusted. Four indicators were used to compare the capabilities of the FPID controller with those of the conventional PID controller in order to evaluate the performance of PLIM in both cases. These indices represent the individual SSE for each operational phase and the total SSE for the entire loading period. According to the simulation results, the FPID works better than a regular PID when used to adjust the operation of DTC-SVM to drive a PLIM to improve the overall system performance. The simulation results using MATLAB Simulink for a PLIM-drive system show that the proposed FPID control provides improved control behavior and operating performance with fast and accurate speed tracking.

Microscopic heterogeneity of low cyclic fatigue damage in Ni-based single crystal superalloy DD413

The heterogeneous low cyclic fatigue damage level in the Ni-based single crystal superalloy DD413 was quantitatively assessed under the strain control of ±0.8% and ± 1.1%. The specimens subjected to ±0.8% strain amplitude exhibited an almost pure elastic deformation response throughout the entire cyclic loading period. In contrast, the ±1.1% strain-controlled deformed specimen exhibited a gradual increase in plastic strain, rising from 0.046% in the 1st cycle to 0.072% by the 268th cycle. The brittle carbides caused a significant mechanical incompatibility with the matrix. This was observed through the orientation dispersal over 16° in the {001} pole figure of the ±1.1% specimen, which was substantially broader than the ±0.8% specimen where the dispersion was only 1.2°. The large orientation gradient in the interdendrite (IR) triggered the dispersion of the microstructure-averaged orientation of the ±1.1% specimen, as evidenced by a mean grain reference orientation deviation (GROD) angle three times higher in the IR compared to the dendrite (DR). While the DR and IR of ±0.8% specimen showed similar mean GROD angles. This substantial orientation gradient was sustained by the high density of geometrically necessary dislocations (GNDs) in the IR, which was double that of the DR. Differently, the DR and IR in the ±0.8% specimen exhibited similar mean densities of GNDs. The study suggests that minimizing microstructural heterogeneity at the dendritic scale may enhance the durability of DD413 alloy components when exposed to cyclical stress with greater strain amplitudes.

Long‐term creep deformation of carbon fiber/epoxy composites with physical aging: Experimental investigation and constitutive modeling

AbstractThe tensile creep tests for two kinds of epoxy resin matrix composite laminates were performed under 25°C and 50°C. Results indicate that these materials deform in a time‐dependent manner, that is, the tensile strain increases within a short time after the tests began, and then decreases during most of the loading period. Such increase and decrease trends reflect the creep characteristic and effect of physical aging, respectively. A linear viscoelastic model is developed to include both the creep temperature effect and physical aging effect, starting from the Boltzmann superposition principle. In modeling, these two effects both contribute to the transient compliance and result in the increase and decrease of the transient compliance. Time–temperature/aging time superposition principle is adopted to deal with the influences of temperature and physical aging. This theoretical model is further implemented numerically within a finite element framework. To verify the newly proposed model, not only the experimental and numerical results of the tensile deformations of laminates are compared, but also the bending deformations of structural components made from the above laminates are analyzed.Highlights Tensile creep tests were done for carbon fiber/epoxy laminates. The strain shows creep temperature and aging effect (TE and AE). New constitutive relation was proposed to describe the TE‐ and AE‐caused strains. Structural‐level flexure creep tests and simulation analyses were conducted.

Reverse Iontophoresis: Noninvasive Assessment of Topical Drug Bioavailability.

Assessing drug disposition in the skin after the application of a topical formulation is difficult. It is hypothesized that reverse iontophoresis (RI), which can extract charged/polar molecules for monitoring purposes, may provide a noninvasive approach for the assessment of local drug bioavailability. The passive and RI extraction of salicylic acid (SA) and nicotine (NIC) from porcine skin in vitro was assessed after a simple solution of the former and a transdermal patch of the latter had been applied for 24 and 8 h, respectively. Immediately after this "passive skin loading", the amount of drug in the stratum corneum (SC) and "viable" tissue (VT) was measured either (a) after tape-stripping and subsequent solvent extraction of both skin layers or (b) following RI extraction over 4 h. Parallel experiments were then performed in vivo in healthy volunteers; in this case, the VT was not sampled and the skin loading period for NIC was only 4 h. RI extraction of both drugs was significantly higher (in vitro and in vivo) than that achieved passively, and the cumulative RI extraction profiles as a function of time were mathematically analyzed using a straightforward compartmental model. Best-fit estimates of drug amounts in the SC and VT (ASC,0 and AVT,0, respectively) at the end of "loading" and two first-order rate constants describing transfer between the model compartments were then determined. The in vitro predictions of ASC,0 and AVT,0 were in excellent agreement with the experimental results, as was the value of the former in vivo. The rate constants derived from the in vitro and in vivo results were also similar. In summary, the results provide proof-of-concept that the RI method has the potential to noninvasively assess relevant metrics of drug bioavailability in the skin.

Numerical simulation of flow and heat transfer in fuel assembly of floating nuclear power platform

ABSTRACT Floating nuclear power platform (FNPP), unlike onshore nuclear power plants, is subjected to periodic rolling loads at sea. These loads will have a more obvious impact on the flow characteristics and temperature distribution inside the fuel assembly (FA). This paper first establishes a refined model of the 7 × 7 core fuel assembly. Then, the flow and heat transfer characteristics of assembly with pure fuel bundles and assembly with guide tubes are analyzed using a segmented grid partitioning method, taking into consideration both accuracy and efficiency in calculation. Finally, the flow and heat transfer characteristics inside the assembly with guide tubes under rolling conditions are simulated and calculated, and compared with the previous simulation results. The calculation results show that the flow and heat transfer characteristics of the assembly with guide tubes are quite different from those of the pure fuel rod bundle assembly, and the rolling environment has obvious adverse effects on the flow field characteristics and temperature distribution in the fuel assembly of the offshore reactor, which must be considered in the design and construction of the floating nuclear power platform. The research results have significant reference value for the design and optimization of floating nuclear power platform assemblies under rolling conditions.

Cumulative trauma load and timing of trauma prior to military deployment differentially influences inhibitory control processing across deployment

Military personnel experience high trauma load that can change brain circuitry leading to impaired inhibitory control and posttraumatic stress disorder (PTSD). Inhibitory control processing may be particularly vulnerable to developmental and interpersonal trauma. This study examines the differential role of cumulative pre-deployment trauma and timing of trauma on inhibitory control using the Go/NoGo paradigm in a military population. The Go/NoGo paradigm was administered to 166 predominately male army combat personnel at pre- and post-deployment. Linear mixed models analyze cumulative trauma, trauma onset, and post-deployment PTSD symptoms on NoGo-N2 and NoGo-P3 amplitude and latency across deployment. Here we report, NoGo-N2 amplitude increases and NoGo-P3 amplitude and latency decreases in those with high prior interpersonal trauma across deployment. Increases in NoGo-P3 amplitude following adolescent-onset trauma and NoGo-P3 latency following childhood-onset and adolescent-onset trauma are seen across deployment. Arousal symptoms positively correlated with conflict monitoring. Our findings support the cumulative trauma load and sensitive period of trauma exposure models for inhibitory control processing in a military population. High cumulative interpersonal trauma impacts conflict monitoring and response suppression and increases PTSD symptoms whereas developmental trauma differentially impacts response suppression. This research highlights the need for tailored strategies for strengthening inhibitory control, and that consider timing and type of trauma in military personnel.

Monitoring system for the construction of buildings in the area of mining exploitation impact

Observations of building structures in mining areas, reveal the occurrence of periodic and permanent excessive loading situations. These include ground deformations associated with the extraction of underground mineral deposits. In urban areas, these deformations significantly alter the operating conditions of building structures. For this reason, forecasts of ground transformation and analyses of possible changes in the technical condition of buildings on the ground surface are made in advance, even before mining is commenced. Taking into account previous in-house experience of the observed effects of mining impacts on building structures, an original method of monitoring changes in the condition of these structures has been developed. The aim of the monitoring is to record phenomena that change the operating conditions of the structures. In the developed method, measurements are made quasi-continuously using strain and deflection sensors mounted directly on structural elements. In the mining area affected by the mining operation being carried out in the years 2020 - 2022, and with a further one planned in the years 2023 - 2024, through the extraction of 14 coal parcels, three public utilities of special interest were monitored. The measurement results of deformation changes in the elements allow for an assessment of changes in the stress state of the structures, and the integration of sensors mounted on the structures into a wireless network fulfils the demands for maintaining public safety conditions in mining areas. It also contributes to the analysis of fatigue issues in masonry structures due to long-term multidirectional loads.

Mathematical Analysis of Aortic Deformation in Aneurysm and Wall Dissection

Aortic dissection is an extremely severe pathology. From the mechanics point of view, the aorta is a multilayered anisotropic reinforced shell, which is subjected to periodic loading under the action of pulse blood pressure. The questions of mathematical modeling of aorta and large arteries dissection are considered. A review of modern mathematical models of aortic and arterial wall structure obtained on the basis of experimental data processing on biaxial stretching of samples is carried out. Mathematical models can be conditionally divided into two classes: 1) effective models, when the internal structure of the wall structure is ignored, but the mechanical parameters of the material "averaged" over the wall thickness are introduced; 2) structured models, when the multilayer (up to three layers) structure of the artery is taken into account with the addition of one to four families of reinforcing fibers. One of the most widely used artery models, the Holzapfel – Hasser – Ogden model, is considered in detail. This model describes a two or three-layered artery with two families of reinforcing fibers. For this model tables of design parameters are given, numerical calculations of arterial rupture and dissection are carried out. The blood vessel is subjected to pulse pressure of blood flowing through it. It is shown that rupture of the inner layer of the vessel leads to an increase in the stress on the outer wall of the vessel. Increasing the thickness and length of the rupture increases the stresses on the outer wall of the vessel. The presence of an aneurysm of the vessel increases stresses twice as much as a vessel without an aneurysm. Splitting of the inner wall of the vessel leads to an increase in stresses on the wall – stresses fall with increasing rupture width for a straight vessel and rise for a vessel with an aneurysm. Stress calculations at the “tip” of delamination showed that the maximum stress is reached at the outer wall of the rupture.

Realizing the load shifting potential of residential space heating - A field study on the control input for thermostatic control of indoor air temperature

Economic model predictive control (MPC) of residential space heating utilizes indoor air temperature fluctuations and thermal mass for load shifting of space heating consumption and it can be used for various demand response purposes in district heating systems. A field experiment imitating the behaviour of an MPC has previously been carried out in three residential buildings in Aalborg, Denmark. Here, digital radiator thermostats were used, and it was found that the load shifting period was cut short when using the temperature measurement embedded in the thermostat as control input for the MPC. Therefore, the field study reported in this paper investigated whether using indoor air temperature sensors as control input for the thermostat improved the realisation of the load shifting. The field study took place in a single-family house in Aarhus, Denmark, and tested the load shifting potential when controlling with either the temperature sensor embedded in the thermostat or an offset between the radiator thermostat setpoint and an indoor air temperature sensor measurement. The study indicates that the use of indoor air temperature measurements as thermostat control input will provide longer periods of loading and unloading the building, thereby increasing the total load shifting potential of the heating consumption.

Improvement of Groin Pain in a Football Player with Femoroacetabular Impingement via a Correction of the Pelvic Position—A Case Report

Background: Femoroacetabular impingement is one possible cause for groin pain and can lead to long periods of absence for football players. In cam impingement, the end-grade position of the leg at kicking makes the hip particularly prone to faulty contact between the acetabulum and the femoral head. Studies suggest that the resting position of the pelvis in the sagittal plane may have an important role in the biomechanics of movement in the presence of cam impingement. Methods: A 19-year-old male competitive footballer complained of sudden groin pain during a period of low athletic load. Biomechanical tests (3D posture and isometric strength analyses) showed that unbalanced individual strength training had resulted in an increased forward tilt of the pelvis. At the same time, cam impingement was confirmed radiologically, which obviously contributed to the sudden onset of the symptoms. The kicking technique of the athlete showed increased hip and trunk flexion, which also indicated a muscular imbalance. Targeted strength and stretching exercises three times a week improved the pelvic position in terms of reduced anteversion. At the same time, the patient performed strength exercises to improve his kicking technique. Results: After 8 weeks, improvements in his pelvic position and global posture and increased muscle strength could be verified. At the same time, the athlete was free of complaints again. Conclusions: When groin pain occurs in football players with cam impingement, special attention should be paid to the resting position of the pelvis in the sagittal plane. Correcting increased pelvic anteversion can prevent unfavourable end-grade collisions of the acetabulum and femoral head during kicking with strong hip flexion and adduction. Possible changes in the pelvic position due to adverse individual strength training performed by young athletes should always be kept in mind.

Physics-Informed Multi-Agent deep reinforcement learning enabled distributed voltage control for active distribution network using PV inverters

With the recent rapid uptake of photovoltaic (PV) resources, the overvoltage condition during low load periods or intermittent renewable generation is one of the most critical challenges for electricity distribution networks. Traditional model-based local or centralized control methods that rely on proper system parameters are difficult to mitigate rapid changes in power systems. Utilizing model-free/data-driven multiagent deep reinforcement learning (MADRL) has been recognized as an effective solution to active voltage control. However, existing MADRL-based control approaches trained solely on data are agnostic to the underlying real-world physics principles. Therefore, this paper aims to incorporate physical knowledge of regional distribution networks into MADRL’s decision-making. The main contributions of this paper are summarized as follows. First, a novel physics-informed MADRL -based distributed voltage control method is proposed, which is still under a centralized training and distributed execution framework and only requires local measurements. Second, graph neural networks are employed to help MADRL agents learn graph knowledge (node features and topological information). Further, transformer is introduced to extract discriminative representations and ensure agents’ cooperative control. Third, we adopt a physics-guided architecture of neural networks in the actor network to stabilize the training process and improve sample efficiency. Finally, simulation results based upon modified IEEE 33-bus and 141-bus networks validate the proposed method's effectiveness, robustness and computation efficiency.