Search Results (11,457)

Mental fatigue is an important factor affecting athletes’ performance. Explaining the effects of mental fatigue on sports performance from a theoretical point of view can help us deeply understand the interconnection between mental fatigue and sports performance and conduct effective interventions based on this. Combining the relevant literature in China and abroad reveals that the current academic theories on the mechanism of sports fatigue include motivational control theory, underload theory, neural waste disposal hypothesis, and resource depletion theory. The effects of mental fatigue on performance are reflected in aerobic endurance, sports decision-making, tactical performance, and technical performance. Current coping strategies for mental fatigue include physiological coping strategies based on nutrition (caffeine), odor, and noninvasive neuromodulation techniques and psychological and behavioral coping strategies based on music and positive thinking. Full article

The periodic changes in climatic factors cause the pavement temperature field to change significantly, resulting in fatigue damage to the pavement caused by temperature stress, and the influence depth has a critical value. To reveal the influence range and variation pattern of the rubber-modified pavement temperature field under frequent rainfall and high temperatures, based on indoor tests and the finite element model, the evolution law of different influencing factors and pavement temperature fields was determined by a single factor sensitivity analysis method. The degree of influence of each influencing factor on the pavement temperature field was analyzed using the Pearson correlation. The results showed that with different asphalt mixture initial temperatures, the road surface temperature decreased from 20 °C to 40 °C under sudden rainfall. Repeated rainfall following high temperatures induces cyclic temperature changes 30 mm below the road surface. The pavement temperature difference increased linearly with the dramatic temperature difference, and the changes in the pavement temperature field were small when the number of cycles exceeded 30. The number of cycles and cycle temperature difference were the main factors affecting the changes in the pavement temperature field under dramatic cooling–heating cycles. Full article

Steel structure flange connections are extensively employed in structural nodes due to their superior mechanical properties. This study combines fatigue testing and theoretical methods to investigate the fatigue performance of high-strength bolts in flange connections under actual gradient descent loads and provide fatigue design methods. Initially, fatigue tests were conducted on two sets of high-strength bolts under a gradient descent loading mode, yielding a total of 11 sets of fatigue data. Subsequently, the stress–life (S-N) curve was plotted using a cumulative damage model combined with an equivalent constant amplitude stress method, and the results were compared with existing fatigue design specifications. Additionally, digital cameras and electron microscopes were utilized to capture fatigue fracture images of the high-strength bolts, allowing a detailed investigation into the mechanisms underlying bolt fatigue fractures. The results indicate that the allowable stress amplitudes for the two sets of high-strength bolts, corresponding to a fatigue life threshold of 2 million cycles, were 144.211 MPa and 130.316 MPa, respectively—both of which exceed the values specified in current fatigue design codes. Moreover, finite element simulations revealed that the most pronounced stress concentration occurs at the first thread where the bolt and nut interface, which is identified as the critical location for fatigue fracture in bolts. The allowable stress and fatigue calculation method of bolts obtained in this study will provide a reference for flange node design Full article

Background: Ketone body supplementation has emerged as a potential ergogenic aid in cycling. Exogenous ketones, primarily in the form of beta-hydroxybutyrate, offer an alternative fuel source, bypassing the need for strict ketogenic diets. However, the science surrounding their efficacy remains complex, with mixed field findings and unexplored mechanisms. Methods: A narrative review of the current literature was conducted, synthesizing studies on the metabolic and cognitive effects of ketone bodies in cycling. The review included an examination of human and mechanistic studies, along with emerging hypotheses on ketone bodies and their role in modulating red blood cell production and recovery processes. Results: Ketone body supplementation can theoretically spare glycogen, reduce muscle protein breakdown, enhance fat oxidation, and improve recovery by mitigating oxidative stress and inflammation. Additionally, ketone bodies may support cognitive function, reducing perceived mental fatigue. Preliminary evidence also suggests a potential role in modulating erythropoietin levels through histone acetylation, though further research is needed to establish its impact on oxygen delivery. Despite the theoretical potential, the practical assessment of field studies shows disappointing effects on performance from ketone body supplementation. Conclusions: While ketone bodies offer several potential benefits for cyclists, the variability in individual responses, lack of long-term data, and inconsistent findings in performance studies highlight the need for further research. Optimizing dosage, timing, and understanding the broader implications of ketone body supplementation will be crucial for their practical application in cycling. Full article

The Ostergren model is simple in form and widely used in engineering practice, also serving as the modeling basis of both the damage differentiation and crack propagation models. However, the shortcomings of the Ostergren model are that the modeling process is affected by thermomechanical fatigue (TMF) test parameters. To establish a TMF life normalized model, a modified Ostergren model based on hysteresis energy damage and TMF data for H13 steel was proposed. The model was successfully applied to TMF life prediction for 4Cr5Mo2V steel. The band of predicted life and test life is basically within the factor of 1.5. In summary, the modified Ostergren model is suitable for the TMF life prediction of Cr-Mo-V-type die-casting die steel. Full article

Background/Objectives: The physical performance and functional status of individuals with long COVID may be altered. Health resort treatment comprises balneology, exercises, physical medicine modalities, and climate therapy. Complex treatment in a sanatorium may have a positive effect on long COVID patients. This study assessed functional status, physical performance, and fatigue in people with long COVID that qualified for the health resort treatment and its efficacy in this group of patients. Methods: A retrospective review of the medical records of 116 patients (66 women and 50 men) undergoing health resort treatment for long COVID in 2021 at the Rehabilitation Hospital and Sanatorium “Gwarek” in Goczałkowice-Zdrój (Poland) was conducted. Data were collected between March and May 2024. Their functional status, physical performance, and level of fatigue were assessed twice: before and after the treatment. Results: After the health resort treatment, their physical performance (10.41 points ± 1.84 points vs. 11.57 points ± 0.94 points; p < 0.00001) and functional status (2.13 points ± 0.88 points vs. 1.23 points ± 0.62 points; p < 0.00001) improved. Their fatigue (4.83 points ± 2.38 points vs. 2.15 points ± 1.31 points; p < 0.00001) level was diminished after the treatment. Conclusions: Fatigue was of moderate intensity in the long COVID patients that qualified for the health resort treatment. Most of the long COVID patients reported mild functional limitations, whereas their physical performance was undisturbed. Health resort treatment improved functioning in patients with persistent COVID-19 symptoms by reducing fatigue, improving their functional capacity and physical performance. It should be recommended as a supplement to the standard treatment because of its complexity. Full article

This article presents the results of experimental studies and numerical calculations that were conducted to analyse the phenomena that occur during the operation of an ingot mould that is designed for casting steel ingots. The studies were conducted on an experimental stand in a foundry on an ingot mould that was designed to make ingots that weigh up to six tons; they consisted of determining the temperature of the ingot mould and measuring the displacements of its walls during filling with steel and cooling. These studies were used to create and verify a numerical model that was used to determine the temperatures, displacements, deformations, and stresses in ingot mould walls during the operating cycle using the FEM method. Microstructure studies of ingot cast iron that was subjected to thermal fatigue were also conducted on a laboratory stand; the temperature changes and test times were the same as those used under the normal operating conditions of the ingot mould. Cast iron samples were subjected to heating and cooling cycles within a range of 0 to 60 cycles; then, tensile tests were performed to determine their stress–strain curves. As a result of the conducted tests, a great influence was found of the number of cycles on decreases in the values of the modulus of elasticity and tensile strength—especially within a range of 0 to 10 cycles. A relationship was also found between the changes in these values and the image of the cast iron microstructure. Based on images of the cast iron microstructure after being subjected to different numbers of thermal fatigue cycles, the mechanism of the crack initiation and propagation was determined. The influence of the changes in the strength of the cast iron and the stress state that was determined by the FEM method on the durability of the tested type of ingot mould was analysed. The obtained research results will be useful for introducing design changes that are aimed at increasing the fatigue durability of ingot moulds. Full article

Background: Hypophosphatasemia is often overlooked despite its potential to indicate underlying pathologies. The aim of this study was to determine the prevalence of persistent hypophosphatasemia in a large, urban, multi-specialty hospital population and characterize the clinical and laboratory findings in adult patients with this condition. Methods: In this retrospective observational study, the results of 424,434 alkaline phosphatase (ALP) tests in 50,136 patients aged ≥18 years that were performed at Okayama University Hospital between July 2020 and October 2023 were analyzed. Persistent hypophosphatasemia was defined as consistently low ALP levels (≤40 IU/L) for 28 days with a minimum recorded level of ≤35 IU/L. Results: Persistent hypophosphatasemia was detected in 273 patients (0.54% of the tested patients), and the patients with persistent hypophosphatasemia included a higher proportion of females (72.5% vs. 52.9% in the people without persistent hypophosphatasemia; chi-squared test, p < 0.01) and had a younger median age (51 years vs. 63 years; Mann–Whitney U test, p < 0.01) than those in the overall tested population. The common causes of persistent hypophosphatasemia were cancer (30%), glucocorticoid use (21%), and immunosuppressants (16%). Notably, 38 patients (14%) had no apparent cause for low ALP values. These patients were categorized on the basis of their clinical characteristics, with some patients presenting symptoms potentially related to adult hypophosphatasia. Conclusions: This study provides prevalence and insights into the causes and characteristics of persistent hypophosphatasemia in a Japanese tertiary care setting. While most cases were associated with known causes, patients with unexplained hypophosphatasemia and symptoms such as chronic pain, muscle weakness, and general fatigue could have adult hypophosphatasia. In such cases, comprehensive evaluation and further investigation for hypophosphatasia should be considered. Persistent hypophosphatasemia of undetermined etiology could be a crucial initial step in diagnostic algorithms for this condition. Full article

Background: Myasthenia gravis (MG) is an autoimmune neuromuscular disease characterized by fatigue and muscle weakness. Previous research has noted a high incidence of psychological problems, particularly anxiety and depression, as well as alterations in sleep quality among patients with MG. The aim of this study was to assess depression, anxiety, sleep problems, and fatigue in individuals with MG and to analyze the relationships among these variables, as well as to determine the influence of corticosteroid use and thymectomy. Methods: The sample consisted of 72 participants, 42 belonging to the clinical group with MG and 30 healthy participants to the control group. The instruments used were Hospital Anxiety and Depression Scale (HADS), Pittsburgh Sleep Quality Index (PSQI), and Fatigue Severity Scale (FSS). Results: The results showed that MG patients exhibited higher levels of fatigue, anxiety, depression, and poorer sleep quality compared to the control group (p < 0.05). Significant differences in sleep quality and anxiety levels were observed between thymectomized and non-thymectomized patients. Additionally, a positive correlation was found between anxiety symptoms and sleep quality. Conclusions: The study demonstrated the presence of anxious and depressive symptoms in patients with MG, as well as poorer sleep quality and increased fatigue, suggesting that MG affects not only neuromuscular function but also the psychological well-being of patients. Full article

The increase in energy demand due to industrial development and urbanization has resulted in the development of large-scale energy facilities. Republic of Korea’s petrochemical industrial complexes serve as prime examples of this phenomenon. However, because of complex processes and aging facilities, many of which have been in operation for over a decade, these industrial complexes are prone to process-deviation-related accidents. Chemical accidents in energy facilities involving high-pressure liquids or gases are especially dangerous; therefore, proactive accident prevention is critical. This study is also relevant to corporate environment, social, and governance (ESG) management. Preventing chemical accidents to protect workers from injury is critical for business and preventing damage to surrounding areas from chemical accidents is a key component of ESG safety. In this study, we collected accident data, specifically injury-related incidents, from Republic of Korea’s petrochemical industrial complexes, which are the foundation of the energy industry. We analyzed the causes of accidents in a step-by-step manner. Furthermore, we conducted a risk analysis by categorizing accident data based on the level of risk associated with each analysis result; we identified the main causes of accidents and “high-risk process stages” that posed significant risk. The analysis reveals that the majority of accidents occur during general operations (50%, 167 cases) and process operations (39%, 128 cases). In terms of incident types, fire/explosion incidents accounted for the highest proportion (43%, 144 cases), followed by leakage incidents (24%, 78 cases). Furthermore, we propose a disaster safety artificial intelligence (AI) model to prevent major and fatal accidents during these high-risk process stages. A detailed analysis reveals that human factors such as accumulated worker fatigue, insufficient safety training, and non-compliance with operational procedures can significantly increase the likelihood of accidents in petrochemical facilities. This finding emphasizes the importance of introducing measurement sensors and AI convergence technologies to help humans predict and detect any issues. Therefore, we selected representative accident cases for implementing our disaster safety model. Full article

Objectives: To evaluate the effect of bio-electromagnetic energy regulation (BEMER) therapy on erectile dysfunction (ED) in patients with multiple sclerosis (MS). Methods: A triple-blind randomized clinical trial was conducted in two different centers. Fifty-two male participants with MS were randomly allocated into two groups. Patients received either three weeks of BEMER with pelvic floor exercises or sham BEMER with pelvic floor exercises. The primary measure was the International Index of Erectile Function—Erectile Function (IIEF-EF). Secondary measures included the Sexual Health Inventory for Men (SHIM), Erection Hardness Scale (EHS), Arizona Sexual Experience Scale (AXES), Modified Fatigue Impact Scale (MFIS), and Multiple Sclerosis, Intimacy, and Sexuality Questionnaire (MSISQ-19). Results: Compared to the sham BEMER group, the BEMER group showed better improvements in the IIEF-EF (mean difference [MD]: −6.9, p < 0.001), SHIM (MD: −6.1, p < 0.001), EHS (MD: −0.4, p = 0.022), AXES (MD: 2.9, p = 0.030), MSISQ-19 (MD: 15.0, p < 0.001), and MFIS (MD: 31.0, p < 0.001). Conclusions: BEMER therapy improved erectile function and sexual satisfaction and reduced fatigue in patients with MS after three weeks of intervention. Long-term follow-up studies are warranted to ascertain the sustained benefits of BEMER therapy for MS-related ED. Full article

Hydrogen production risers (HPRs) connected to floating offshore wind turbines (FOWTs) must be properly configured to minimize both the top-end tension at the hang-off point and the oscillation amplitude in the touchdown zone (TDZ) under environmental loads. One of the best riser configurations to meet these requirements is the lazy-wave configuration, where the riser is lifted midway by buoyancy tanks to create a negative curvature, mitigating the motion dependency of the catenary part and the TDZ. Analytical solutions can be effectively used in riser optimization and configuration studies, where a large number of analyses need to be conducted iteratively. In this paper, an analytical model for HPRs has been developed by combining different approaches for the hanging and touchdown zones to improve the accuracy and continuity of shear force, bending moment, and axial tension distribution along the riser, which are the key parameters governing fatigue damage accumulation in the TDZ. Modified catenary equations were used for the hanging part, and a boundary layer model was implemented in the touchdown zone to model the seabed interaction, preventing stress discontinuity between the two sections. The model was used to assess a case study and compared with numerical simulations to ensure accuracy and viability. The proposed model can be used in daily engineering practice for preliminary investigations and optimization studies of HPRs. Full article

When cracks appear in reinforced concrete (RC) structures, the tensile load will be borne by steel bars with high ductility, resulting in a large deformation. Traditional strain sensors have difficulties in achieving good performance for large deformations in concrete structures. In this paper, based on a laser-induced graphene (LIG) technique, a flexible sensor is proposed for monitoring large deformations of concrete structures. Polyimide film is used as the carbon precursor to prepare LIG through laser scanning and then LIG is transferred onto a polydimethylsiloxane (PDMS) substrate to form the flexible sensor. The calibration and performance verification of the flexible sensor are completed through tensile tests. The applicability of the flexible sensor in monitoring large deformations of concrete is verified through beam bending experiments. The fatigue resistance of the flexible sensor is verified through fatigue tests on a full-scale beam. The experimental results showed that the flexible sensor has the advantages of low cost, simple preparation, and stable performance, making it suitable for applications in the field of large deformation monitoring of RC structures. Full article

This study describes the features, manifestations and interrelationships of job stress, working capacity, professional performance and safety in loggers with a shift work organization in the North. This study involved 402 loggers. The research methods include questionnaires and psychophysiological diagnostics of stress and working capacity as well as questionnaires on the professional performance and safety of workers. The following statistical methods were used: correlation, multivariate dispersion and multi-regression stepwise analysis. It was found that the severity of stress, speed, accuracy and operator working capacity, as well as well-being, activity and mood in logging equipment operators, timber truck drivers and maintenance specialists statistically differ significantly. Higher professional stress and a more frequent decrease in professional performance are characteristic of truck drivers. Psychological and psychophysiological job stress and working capacity parameters are associated with the professional performance parameters of loggers. According to the results of a number of multi-regression analyses, the reduced professional performance markers of loggers include the index of stress, satiety, monotony and fatigue, vegetative balance and stress (method of M. Luscher and coefficients from G.A. Aminev), operator working capacity and reaction speed (CVMR). Full article

In this paper, the fatigue resistance of a full-scale Steel Catenary Riser (SCR) girth weld is investigated using the Strength–Number of cycles (S–N) curve method based on weld formation quality and fracture mechanics approaches. The test results, presented in the form of S–N curves, are superior to the design curve E in BS 7608. Compared with the S–N curve determined by a resonant bending rig, the analytical fracture mechanics, i.e., engineering critical assessment (ECA) based on BS 7910, can provide a rational estimation of full-scale girth welds. For the numerical methods, the short crack growth phase is crucial to improving the accuracy and reliability of the assessment. For the girth weld with a concave root, the geometries of the weld cap are the predominant factors for fatigue life. Although the crack initiation site is always located at the outer surface regardless of the flushed or welded caps, the weld grinding treatment is still effective in promoting fatigue life. Full article