Search Results (299)

This study investigates the hot deformation behaviour and flow stress prediction of metastable β-Ti-15Mo alloy, a promising material for biomedical applications requiring strength–modulus optimisation and thermomechanical tunability. Isothermal compression tests were performed within the temperature range of 923–1173 K and at strain rates of 0.17, 1.72, and 17.2 ${\mathrm{s}}^{-1}$ to assess the material’s response under industrially relevant hot working conditions. The alloy showed significant sensitivity to temperature and strain rate, with dynamic recovery (DRV) and dynamic recrystallisation (DRX) dominating the softening behaviour depending on the conditions. A strain-compensated Arrhenius-type constitutive model was developed and validated, resulting in an apparent activation energy of approximately 234 kJ/mol. Zener–Hollomon parameter analysis confirmed a transition in deformation mechanisms. Although microstructural and diffraction data suggest possible contributions from nanoscale phase transformations, including ω-phase dissolution at high temperatures, these aspects remain to be fully elucidated. The model offers reliable predictions of flow behaviour and supports optimisation of thermomechanical processing routes for biomedical β-Ti alloys. Full article

The high cost of hydrogen production is the primary factor limiting the development of the hydrogen energy industry chain. Additionally, due to the inefficiency of hydrogen production by water electrolysis technology, the development of high-performance catalysts is an effective means of producing low-cost hydrogen. In water electrolysis technology, the electrocatalytic activity of the electrode affects the kinetics of the oxygen evolution reaction (OER) and the hydrogen evolution rate. This study utilizes the liquid phase co-precipitation method to synthesize three types of Prussian blue analog (PBA) electrocatalytic materials: Fe/PBA(Fe₄[Fe(CN)₆]₃), Fe-Mn/PBA((Fe, Mn)₃[Fe(CN)₆]₂·nH₂O), and Fe-Mn-Co/PBA((Mn, Co, Fe)₃^II[Fe^III(CN)₆]₂·nH₂O). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that Fe-Mn-Co/PBA has a smaller particle size and higher crystallinity, and its grain boundary defects provide more active sites for electrochemical reactions. The electrochemical test shows that Fe-Mn-Co/PBA exhibits the best electrochemical performance. The overpotential of the oxygen evolution reaction (OER) under 1 M alkaline electrolyte at 10/50 mA·cm⁻² is 270/350 mV, with a Tafel slope of 48 mV·dec⁻¹, and stable electrocatalytic activity is maintained at 5 mA·cm⁻². All of these are attributed to the synergistic effect of Fe, Mn, and Co metal ions, grain refinement, and the generation of grain boundary defects and internal stresses. Full article

The constitutive model is widely employed to characterize the rheological properties of metallic materials under high-temperature conditions. It is typically derived from a series of high-temperature tests conducted at varying deformation temperatures, strain rates, and strains, including hot stretching, hot compression, separated Hopkinson pressure bar testing, and hot torsion. The original experimental data used for establishing the constitutive model serves as the foundation for developing phenomenological models such as Arrhenius and Johnson–Cook models, as well as physical-based models like Zerilli–Armstrong or machine learning-based constitutive models. The resulting constitutive equations are integrated into finite element analysis software such as Abaqus, Ansys, and Deform to create custom programs that predict the distributions of stress, strain rate, and temperature in materials during processes such as cutting, stamping, forging, and others. By adhering to these methodologies, we can optimize parameters related to metal processing technology; this helps to prevent forming defects while minimizing the waste of consumables and reducing costs. This study provides a comprehensive overview of commonly utilized experimental equipment and methods for developing constitutive models. It discusses various types of constitutive models along with their modifications and applications. Additionally, it reviews recent research advancements in this field while anticipating future trends concerning the development of constitutive models for high-temperature deformation processes involving metallic materials. Full article

The pull-back method for determining dynamic tensile strength assumes one-dimensional stress wave propagation and material homogeneity. This study validates these assumptions for unidirectional reinforced concrete (UDRC) through experiments and numerical simulations. Split Hopkinson pressure bar tests were conducted on plain concrete, plain UDRC, and deformed UDRC specimens containing a central 6 mm steel bar. Ultra-high-speed digital image correlation at 500,000 fps enabled precise local strain rate measurements (3 s⁻¹ to 55 s⁻¹) at fracture locations. Finite element simulations revealed that while reinforcement induces localized multi-axial stresses near the steel–concrete interface, the bulk concrete maintains predominantly uniaxial stress conditions. Experimental results showed less than 1% variation in pull-back velocity between specimen types. Statistical analysis confirmed a unified strain rate-strength relationship: ${\sigma }_{\mathrm{spall}}=4.1+4.7{log}_{10}\left(\dot{\epsilon }\right)$$\mathrm{M}\mathrm{Pa}$, independent of reinforcement configuration (ANCOVA: $p=0.2182$ for interaction term). The dynamic tensile strength is governed by concrete matrix properties rather than reinforcement type. These findings are the first to experimentally and numerically validate the pull-back method’s applicability to UDRC systems, establishing that dynamic tensile failure is matrix-dominated and enabling simplified one-dimensional analysis for reinforced concrete under impact. Full article

This paper, based on the Johnson–Cook damage model, investigates the damage mechanism of high-strength steel tailor welded blanks (TWBs) (Usibor1500P and Ductibor500) during the forming process. Initially, specimens with varying notch sizes were designed and fabricated to perform uniaxial tensile tests to determine their mechanical properties. Then, the deformation process of the notched specimens was simulated using finite element software, revealing the distribution and variation of stress triaxiality at the fracture surface. By combining both experimental and simulation data, the parameters of the Johnson–Cook (J–C) damage model were calibrated, and the effects of temperature, strain rate, and stress triaxiality on material fracture behavior were further analyzed. Based on finite element analysis, the relevant coefficients for stress triaxiality, strain rate, and temperature were systematically calibrated, successfully establishing a J–C fracture criterion for TWB welds, Usibor1500P, and Ductibor500 high-strength steels. Finally, the calibrated damage model was further validated through the Nakajima-type bulge test, and the simulated Forming Limit Diagram (FLD) closely matched the experimental data. The results show that the analysis based on the J–C damage model can effectively predict the fracture behavior of tailor welded blanks (TWB) during the forming process. This study provides reliable numerical predictions for the damage behavior of high-strength steel laser-customized welded sheets and offers a theoretical basis for engineering design and material performance optimization. Full article

This study investigates the influence of rotation on wave propagation in a semiconducting nanostructure thermoelastic solid subjected to a ramp-type heat source within a two-temperature model. The thermoelastic interactions are modeled using the two-temperature theory, which distinguishes between conductive and thermodynamic temperatures, providing a more accurate description of thermal and mechanical responses in semiconductor materials. The effects of rotation, ramp-type heating, and semiconductor properties on elastic wave propagation are analyzed theoretically. Governing equations are formulated and solved analytically, with numerical simulations illustrating the variations in thermal and elastic wave behavior. The key findings highlight the significant impact of rotation, nonlocal parameters $e_{0}a$, and time derivative fractional order (FO) $\alpha$ on physical quantities, offering insights into the thermoelastic performance of semiconductor nanostructures under dynamic thermal loads. A comparison is made with the previous results to show the impact of the external parameters on the propagation phenomenon. The numerical results show that increasing the rotation rate $\mathsf{\Omega }=5$ causes a phase lag of approximately 22% in thermal and elastic wave peaks. When the thermoelectric coupling parameter ${\mathsf{\epsilon }}_3$ is increased from $-0.8\times {10}^{-42}$ to $1.2\times {10}^{-42}$. The temperature amplitude rises by 17%, while the carrier density peak increases by over 25%. For nonlocal parameter values $\mathsf{\epsilon }=0.3\to 0.6$, high-frequency stress oscillations are damped by more than 35%. The results contribute to the understanding of wave propagation in advanced semiconductor materials, with potential applications in microelectronics, optoelectronics, and nanoscale thermal management. Full article

Insulation materials are critical for the reliability and performance of electrical power systems, particularly in high-voltage rotating machines. While failures can arise from thermal, mechanical, or electrical stress, they predominantly manifest as electrical breakdowns. Prior research has primarily concentrated on aging in straight winding sections, despite evidence indicating that failures frequently occur in the bending regions of turn insulation. This study explores the influence of high-frequency pulsed electrical stress on the lifetime behavior of Type II insulation systems used in high-voltage rotating machines. Practical samples, designed with geometric configurations and technology akin to that in rotating machines, were tested under conditions characterized by voltage slew rates (dv/dt) exceeding 10 kV/μs, with variations in frequency and waveform shape. The findings reveal that the rate of electrical aging remains consistent across differing pulse widths, risetimes, and polarities, displaying a similar lifetime exponent. Nonetheless, insulation durability is markedly more compromised under pulsed conditions. At the identical times-to-failure, the sinusoidal waveform necessitated nearly twice the applied peak voltage as the bipolar pulse waveform. This finding clearly suggests that pulsed excitation exacerbates insulation degradation more effectively due to the sharp rise times and high (dv/dt) rates imposing substantial electrical stress on dielectric materials. Full article

Caragana korshinskii Kom. (CKB), widely cultivated in Inner Mongolia, China, has potential for silage feed development due to its favorable nutritional characteristics, including a crude protein content of 14.2% and a neutral detergent fiber content below 55%. However, its vascular bundle fiber structure limits the efficiency of lactic acid conversion and negatively impacts silage quality, which can be improved through mechanical crushing. Currently, conventional crushing equipment generally suffers from uneven particle size distribution, high energy consumption, and low processing efficiency. In this study, a layered aggregate model was constructed using the discrete element method (DEM), and the Hertz–Mindlin with Bonding contact model was employed to characterize the heterogeneous mechanical properties between the epidermis and the core. Model accuracy was enhanced through reverse engineering and a multi-particle-size filling strategy. Key parameters were optimized via a Box–Behnken experimental design, with a core normal stiffness of 7.37 × 10¹¹ N·m⁻¹, a core shear stiffness of 9.46 × 10¹⁰ N·m⁻¹, a core shear stress of 2.52 × 10⁸ Pa, and a skin normal stiffness of 4.01 × 10⁹ N·m⁻¹. The simulated values for bending, tensile, and compressive failure forces had relative errors of less than 10% compared to experimental results. The results showed that rectangular hammers, due to their larger contact area and more uniform stress distribution, reduced the number of residual bonded contacts by 28.9% and 26.5% compared to stepped and blade-type hammers, respectively. Optimized rotational speed improved dynamic crushing efficiency by 41.3%. The material exhibited spatial heterogeneity, with the mass proportion in the tooth plate impact area reaching 43.91%, which was 23.01% higher than that in the primary hammer crushing area. The relative error between the simulation and bench test results for the crushing rate was 6.18%, and the spatial distribution consistency reached 93.6%, verifying the reliability of the DEM parameter calibration method. This study provides a theoretical basis for the structural optimization of crushing equipment, suppression of circulation layer effects, and the realization of low-energy, high-efficiency processing. Full article

The type of non-professional or professional support received affects the quality of life of the patient and their caregivers. Social support is the type of interaction that is taken by the patient and his caregivers in a problematic, difficult, stressful, or critical situation. Aim: The aim of the study was to assess the impact of social support on the functioning of patients under nursing home care. Material and methods: The study included 148 chronically ill patients under home nursing care. The study used the diagnostic survey method; the research technique was a questionnaire containing basic data about the respondent and the Social Support Scale (SWS) by Krystyna Kmiecik-Baran. Results: The need to continue the causal treatment at home means that the main source of support for care beneficiaries are nurses who provide medical services at the patient’s home, supported by doctors and family members of the patient. According to patients’ subjective assessment of the support they received from nurses, patients rated the informational support provided by nurses highest at 14.3 points and emotional support at 13.3 points (SD 1.776). on a scale where the maximum score was 16 points. In the opinion of the surveyed patients, the value-added support provided was the lowest-rated category by patients, 9.74 points (SD 2.505). Instrumental support was also rated very poorly by the respondents (10.17 points (SD 2.069). In each category, there was no statistically significant difference at the p < 0.05 level in the respondents’ evaluation, which means that the expressed opinion on each type of support from the highest to the lowest evaluation: informational, emotional, instrumental, and evaluative—overlapped in the patient group and the family group. Conclusions: Patients under home care highly appreciated the support provided to them by the nursing staff. Social support for a chronically ill person who requires constant care and care by the nursing staff is a form of direct impact that relieves stress and tension, minimizes the effects of the disease, directly affects the course of treatment and care, and prevents stigmatization. Full article

Aiming at the problems of serious pavement temperature diseases, low efficiency and high loss of ice-breaking methods, high occupancy rate of waste tires and the low utilization rate and insufficient durability of rubber particles, this paper aims to improve the service level of roads and ensure the safety of winter pavements. A pavement material with high efficiency, low carbon and environmental friendliness for active snow melting and ice breaking is developed. Firstly, NaOH, NaClO and KH550 were used to optimize the treatment of rubber particles. The hydrophilic properties, surface morphology and phase composition of rubber particles before and after optimization were studied, and the optimal treatment method of rubber particles was determined. Then, the optimized rubber particles were used to replace the natural aggregate in the polyurethane gel mixture by the volume substitution method, and the optimum polyurethane gel dosages and molding and curing processes were determined. Finally, the influence law of the road performance of RPGM was compared and analyzed by means of an indoor test, and the ice-breaking effect of RPGM was explored. The results showed that the contact angles of rubber particles treated with three solutions were reduced by 22.5%, 30.2% and 36.7%, respectively. The surface energy was improved, the element types on the surface of rubber particles were reduced and the surface impurities were effectively removed. Among them, the improvement effect of the KH550 solution was the most significant. With the increase in rubber particle content from 0% to 15%, the dynamic stability of the mixture gradually increases, with a maximum increase of 23.5%. The maximum bending strain increases with the increase in its content. The residual stability increases first and then decreases with the increase in rubber particle content, and the increase ranges are 1.4%, 3.3% and 0.5%, respectively. The anti-scattering performance increases with the increase in rubber content, and an excessive amount will lead to an increase in the scattering loss rate, but it can still be maintained below 5%. The fatigue life of polyurethane gel mixtures with 0%, 5%, 10% and 15% rubber particles is 2.9 times, 3.8 times, 4.3 times and 4.0 times higher than that of the AC-13 asphalt mixture, respectively, showing excellent anti-fatigue performance. The friction coefficient of the mixture increases with an increase in the rubber particle content, which can be increased by 22.3% compared with the ordinary asphalt mixture. RPGM shows better de-icing performance than traditional asphalt mixtures, and with an increase in rubber particle content, the ice-breaking ability is effectively improved. When the thickness of the ice layer exceeds 9 mm, the ice-breaking ability of the mixture is significantly weakened. Mainly through the synergistic effect of stress coupling, thermal effect and interface failure, the bonding performance of the ice–pavement interface is weakened under the action of driving load cycle, and the ice layer is loosened, broken and peeled off, achieving efficient de-icing. Full article

Persons with personality type D are characterized by an “unhealthy lifestyle”, which is manifested by low physical activity, less healthy eating behavior, and failure to comply with doctors’ recommendations. Persons with personality type D have an inadequate response of hemodynamic parameters to psychoemotional stress; the response of other parameters has not been sufficiently studied. The aim of this study was to investigate the association of personality type D with various psychophysiological parameters of the body during mental stress in healthy individuals. Material and Methods: The study involved 79 students of Kemerovo State Medical University aged 18 to 32 years (mean age 20.7 ± 2.4 years). Psychophysiological diagnostics was carried out using the BOSLAB complex; electromyogram, electrocardiogram, body temperature, respiration, galvanic skin response, and photoplethysmogram data were recorded. The stress testing protocol included cognitive tasks and recovery phases. Additionally, the presence of personality type D in students was assessed using the DS-14 questionnaire. The results of stress tests were compared in groups with the presence/absence of type D. Results: The frequency of detection of type D was high (54.4%). When examining the response of psychophysiological parameters, the most pronounced response to stress tests with mental load was noted for heart rate variability and respiratory system parameters. Individuals with type D personality showed more pronounced sympathetic activation in response to mental stress and a slower recovery at rest. Among the studied parameters, association with personality type D was noted for the following indicators during the mental arithmetic test: heart rate (p = 0.022), the Baevsky strain index (p = 0.004), respiratory rate (p = 0.020), and an indicator of regulatory process adequacy (p < 0.001). Conclusion: In the present study, we found differences in the reaction of psychophysiological parameters to mental stress in healthy individuals depending on the presence or absence of personality type D. These data can be useful for developing stress resistance programs and biofeedback training. The possibility of using the above psychophysiological parameters in biofeedback training programs for individuals with personality type D requires further research. Full article

Introduction: People with disabilities are characterized by suboptimal health and lower self-rating health. Their need for health care is greater, they often have a higher prevalence of health problems and they have more difficulty accessing health care. The aim of this study was to assess the health behaviors and health indicators of 12–18-year-old young people with intellectual disabilities and autism spectrum disorder, and to explore their school-related perceptions in the Northern Great Plain region of Hungary. Materials and Methods: A cross-sectional questionnaire survey was conducted with the participation of 185 young people. A custom questionnaire was used, based on the Health Behavior in School-aged Children (HBSC) survey, assessing eating habits, oral care, physical activity, mental well-being, and self-reported health status. The sample was categorized into three groups: the ID1 (Intellectual Disability level 1) group, encompassing young individuals with mild intellectual disability; the ID2 group, encompassing young people with moderate intellectual disability; and the ID+ASD group, encompassing young individuals affected by both intellectual disability and autism spectrum disorder. Results: Consumption of various food types was below optimal levels. Low intake of fruits and vegetables was common, with only 21.6% of the respondents consuming fruit daily and 23.8% consuming vegetables daily. ID1 group reported significantly higher rates of nervousness several times a week (17.8% vs. 5.6% and 6.9%, p < 0.001), sleep difficulties (28.8% vs. 7.4% and 15.5%, p = 0.032), and dizziness (9.6% vs. 1.9% and 3.4%, p = 0.022) compared to the other two groups. A third school-related factor, related to negative emotions, showed a near-significant difference (p = 0.064), suggesting that students with both autism spectrum disorder and intellectual disability perceive lower levels of acceptance from teachers. On school-free days, computer usage was significantly highest in the ID+ASD group; 50% of them used a computer for at least 4 h per day. Conclusions: To improve mental well-being among affected children, psychological support and the implementation of mental health programs are recommended. In addition to teaching stress management techniques and coping mechanisms, integrating relaxation techniques into comprehensive developmental programs—both individually and in groups—is advised. For teachers, it is recommended to acquire disability-specific communication strategies. Full article

The 2014 Mt. Ontake eruption in Japan highlighted the need for improved volcanic shelters. To contribute to their reinforcement, this study focuses on the energy absorption characteristics of pumice, particularly artificial pumice made from waste glass. Compression tests were conducted under unconfined and oedometric conditions using a universal testing machine, drop-weight testing machine, and split Hopkinson bar across a wide strain rate range (10⁻³ to 10² s⁻¹). The deformation behavior was categorized into two types: one with a distinct initial peak followed by stress drop and another with a continuous transition to plateau deformation. Regardless of deformation type, the absorbed energy showed a positive dependence on strain rate. The average absorbed energy increased from approximately 1.6 MJ/m³ at 10⁻³ s⁻¹ to over 4.3 MJ/m³ at 10² s⁻¹. A simple predictive model was proposed to evaluate the energy absorption capacity of pumice reinforcement. The model’s predictions were in good agreement with experimental results for pumice layers up to 150 mm thick. These findings provide fundamental insights into the high strain rate behavior of artificial pumice and its potential application as a passive energy-absorbing material for impact-resistant volcanic shelters. Full article

Modern requirements for aluminum alloys used in mechanical engineering and aviation include increased strength characteristics and refined microstructure. One of the promising methods for improving the properties of aluminum alloys is rolling on a three-high skew rolling mill, which provides intense plastic deformation and a fine-grained structure. This study describes the results of numerical modeling of the rolling process of aluminum alloy 6082 rods in a three-high skew-type mill. Numerical modeling of alloy 6082 was conducted using the ForgeNxT 2.1 software designed to simulate metal-forming processes, including rolling. The rheological behavior of the material under study was investigated by compression tests using a Gleeble 3800 plastometer (“DSI”, Austin, TX, USA), which enabled the determination of the main parameters of material flow under specified conditions. The process of rolling bars of alloy 6082 on a three-high skew mill was numerically analyzed in the temperature range of 350–400 °C. This allowed for the study of the distribution of stresses, temperatures, and strain rates from the rolling mode. A physical experiment was conducted to validate the results of numerical modeling. The obtained results enabled the identification of rolling modes that promote microstructure refinement and enhance the mechanical properties of the alloy. Full article

High temperatures in summer often trigger disease outbreaks in shrimp, resulting in significant economic losses. To investigate the heat tolerance mechanisms of Penaeus monodon, juvenile tiger shrimp were subjected to a high-temperature stress of 38 °C for 144 h. The cumulative survival rate of shrimp sharply decreased to 5.29% in the later 144 h. The heat-sensitive shrimps (S group) were collected in the first 24 h, while those that survived beyond 120 h were collected as the heat-tolerant group (T group). The hepatopancreas of two groups was subjected to transcriptomic and metabolomic analysis. The results revealed that, compared to the S group, the T group exhibited a total of 3527 DEGs, including 2199 upregulated and 1328 downregulated genes. Additionally, 353 DAMs were identified in the T group, with 75 metabolites showing increased levels and 278 metabolites displaying decreased levels. The results revealed that the mechanisms of heat tolerance involve energy supply strategies, immune system regulation, amino acid metabolism, and glutathione metabolism. Energy supply strategies include the digestion and absorption of carbohydrates and proteins, glycolysis/gluconeogenesis, fructose and mannose metabolism, and pyruvate metabolism, all of which collectively meet energy demands in high-temperature environments. The immune system is regulated by C-type lectin receptor pathways and IL-17 signaling pathways, which together coordinate innate immunity to prevent pathogen invasion. In amino acid metabolism, various glycogenic amino acids, such as histidine, phenylalanine, valine, and serine, are metabolized for energy, while excess ammonia is converted to γ-glutamyl-glutamate and L-glutamate to mitigate ammonia accumulation. Combined transcriptomic and metabolomic analyses further indicate that glutathione metabolism plays a crucial role in the adaptation of P. monodon to high-temperature environments. This study explains the high-temperature tolerance mechanism of P. monodon from the aspects of gene expression regulation and material metabolism regulation and also provides a scientific basis and basic data for the selection and breeding of new varieties of P. monodon with a high-temperature tolerance. Full article